Merge pull request #2350 from iced-rs/theming-revolutions

Theming Revolutions

Cargo.toml

@@ -52,7 +52,7 @@ highlighter = ["iced_highlighter"]
 # Enables experimental multi-window support.
 multi-window = ["iced_winit/multi-window"]
 # Enables the advanced module
-advanced = []
+advanced = ["iced_widget/advanced"]
 # Enables embedding Fira Sans as the default font on Wasm builds
 fira-sans = ["iced_renderer/fira-sans"]
 # Enables auto-detecting light/dark mode for the built-in theme

core/src/widget/text.rs

@@ -18,6 +18,7 @@ pub use text::{LineHeight, Shaping};
 #[allow(missing_debug_implementations)]
 pub struct Text<'a, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     content: Cow<'a, str>,
@@ -29,18 +30,16 @@ where
     vertical_alignment: alignment::Vertical,
     font: Option<Renderer::Font>,
     shaping: Shaping,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Theme, Renderer> Text<'a, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Create a new fragment of [`Text`] with the given contents.
-    pub fn new(content: impl Into<Cow<'a, str>>) -> Self
+    pub fn new(content: impl Into<Cow<'a, str>>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Text {
             content: content.into(),
             size: None,
@@ -51,7 +50,7 @@ where
             horizontal_alignment: alignment::Horizontal::Left,
             vertical_alignment: alignment::Vertical::Top,
             shaping: Shaping::Basic,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -75,25 +74,6 @@ where
         self
     }
 
-    /// Sets the style of the [`Text`].
-    pub fn style(mut self, style: impl Fn(&Theme) -> Appearance + 'a) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
-    /// Sets the [`Color`] of the [`Text`].
-    pub fn color(self, color: impl Into<Color>) -> Self {
-        self.color_maybe(Some(color))
-    }
-
-    /// Sets the [`Color`] of the [`Text`], if `Some`.
-    pub fn color_maybe(mut self, color: Option<impl Into<Color>>) -> Self {
-        let color = color.map(Into::into);
-
-        self.style = Box::new(move |_theme| Appearance { color });
-        self
-    }
-
     /// Sets the width of the [`Text`] boundaries.
     pub fn width(mut self, width: impl Into<Length>) -> Self {
         self.width = width.into();
@@ -129,6 +109,42 @@ where
         self.shaping = shaping;
         self
     }
+
+    /// Sets the style of the [`Text`].
+    #[must_use]
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the [`Color`] of the [`Text`].
+    pub fn color(self, color: impl Into<Color>) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.color_maybe(Some(color))
+    }
+
+    /// Sets the [`Color`] of the [`Text`], if `Some`.
+    pub fn color_maybe(self, color: Option<impl Into<Color>>) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        let color = color.map(Into::into);
+
+        self.style(move |_theme| Style { color })
+    }
+
+    /// Sets the style class of the [`Text`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 /// The internal state of a [`Text`] widget.
@@ -138,6 +154,7 @@ pub struct State<P: Paragraph>(P);
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Text<'a, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn tag(&self) -> tree::Tag {
@@ -182,15 +199,15 @@ where
         tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         _cursor_position: mouse::Cursor,
         viewport: &Rectangle,
     ) {
         let state = tree.state.downcast_ref::<State<Renderer::Paragraph>>();
-        let appearance = (self.style)(theme);
+        let style = theme.style(&self.class);
 
-        draw(renderer, style, layout, state, appearance, viewport);
+        draw(renderer, defaults, layout, state, style, viewport);
     }
 }
 
@@ -250,7 +267,7 @@ pub fn draw<Renderer>(
     style: &renderer::Style,
     layout: Layout<'_>,
     state: &State<Renderer::Paragraph>,
-    appearance: Appearance,
+    appearance: Style,
     viewport: &Rectangle,
 ) where
     Renderer: text::Renderer,
@@ -281,7 +298,7 @@ pub fn draw<Renderer>(
 impl<'a, Message, Theme, Renderer> From<Text<'a, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(
@@ -293,7 +310,7 @@ where
 
 impl<'a, Theme, Renderer> From<&'a str> for Text<'a, Theme, Renderer>
 where
-    Theme: DefaultStyle + 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer,
 {
     fn from(content: &'a str) -> Self {
@@ -304,7 +321,7 @@ where
 impl<'a, Message, Theme, Renderer> From<&'a str>
     for Element<'a, Message, Theme, Renderer>
 where
-    Theme: DefaultStyle + 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(content: &'a str) -> Self {
@@ -314,30 +331,38 @@ where
 
 /// The appearance of some text.
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Color`] of the text.
     ///
     /// The default, `None`, means using the inherited color.
     pub color: Option<Color>,
 }
 
-/// The style of some [`Text`].
+/// The theme catalog of a [`Text`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of this [`Catalog`].
+    type Class<'a>;
 
-/// The default style of some [`Text`].
+    /// The default class produced by this [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of some [`Text`].
+
-    fn default_style(&self) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, item: &Self::Class<'_>) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Text`].
-    fn default_style(&self) -> Appearance {
+///
-        Appearance::default()
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
-    }
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
-}
+
-
+impl Catalog for Theme {
-impl DefaultStyle for Color {
+    type Class<'a> = StyleFn<'a, Self>;
-    fn default_style(&self) -> Appearance {
+
-        Appearance { color: Some(*self) }
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(|_theme| Style::default())
+    }
+
+    fn style(&self, class: &Self::Class<'_>) -> Style {
+        class(self)
     }
 }

examples/component/src/main.rs

@@ -73,10 +73,7 @@ mod numeric_input {
 
     impl<Message, Theme> Component<Message, Theme> for NumericInput<Message>
     where
-        Theme: text::DefaultStyle
+        Theme: text::Catalog + button::Catalog + text_input::Catalog + 'static,
-            + button::DefaultStyle
-            + text_input::DefaultStyle
-            + 'static,
     {
         type State = ();
         type Event = Event;
@@ -151,10 +148,7 @@ mod numeric_input {
     impl<'a, Message, Theme> From<NumericInput<Message>>
         for Element<'a, Message, Theme>
     where
-        Theme: text::DefaultStyle
+        Theme: text::Catalog + button::Catalog + text_input::Catalog + 'static,
-            + button::DefaultStyle
-            + text_input::DefaultStyle
-            + 'static,
         Message: 'a,
     {
         fn from(numeric_input: NumericInput<Message>) -> Self {

examples/gradient/src/main.rs

@@ -60,7 +60,7 @@ impl Gradient {
         } = *self;
 
         let gradient_box = container(horizontal_space())
-            .style(move |_theme, _status| {
+            .style(move |_theme| {
                 let gradient = gradient::Linear::new(angle)
                     .add_stop(0.0, start)
                     .add_stop(1.0, end);

examples/layout/src/main.rs

@@ -81,10 +81,10 @@ impl Layout {
         } else {
             self.example.view()
         })
-        .style(|theme, _status| {
+        .style(|theme| {
             let palette = theme.extended_palette();
 
-            container::Appearance::default()
+            container::Style::default()
                 .with_border(palette.background.strong.color, 4.0)
         })
         .padding(4)
@@ -245,10 +245,10 @@ fn application<'a>() -> Element<'a, Message> {
         .padding(10)
         .align_items(Alignment::Center),
     )
-    .style(|theme, _status| {
+    .style(|theme| {
         let palette = theme.extended_palette();
 
-        container::Appearance::default()
+        container::Style::default()
             .with_border(palette.background.strong.color, 1)
     });
 

examples/pane_grid/src/main.rs

@@ -338,39 +338,30 @@ mod style {
     use iced::widget::container;
     use iced::{Border, Theme};
 
-    pub fn title_bar_active(
+    pub fn title_bar_active(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
-        container::Appearance {
+        container::Style {
             text_color: Some(palette.background.strong.text),
             background: Some(palette.background.strong.color.into()),
             ..Default::default()
         }
     }
 
-    pub fn title_bar_focused(
+    pub fn title_bar_focused(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
-        container::Appearance {
+        container::Style {
             text_color: Some(palette.primary.strong.text),
             background: Some(palette.primary.strong.color.into()),
             ..Default::default()
         }
     }
 
-    pub fn pane_active(
+    pub fn pane_active(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
-        container::Appearance {
+        container::Style {
             background: Some(palette.background.weak.color.into()),
             border: Border {
                 width: 2.0,
@@ -381,13 +372,10 @@ mod style {
         }
     }
 
-    pub fn pane_focused(
+    pub fn pane_focused(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
-        container::Appearance {
+        container::Style {
             background: Some(palette.background.weak.color.into()),
             border: Border {
                 width: 2.0,

examples/scrollable/src/main.rs

@@ -341,8 +341,8 @@ impl Default for ScrollableDemo {
     }
 }
 
-fn progress_bar_custom_style(theme: &Theme) -> progress_bar::Appearance {
+fn progress_bar_custom_style(theme: &Theme) -> progress_bar::Style {
-    progress_bar::Appearance {
+    progress_bar::Style {
         background: theme.extended_palette().background.strong.color.into(),
         bar: Color::from_rgb8(250, 85, 134).into(),
         border: Border::default(),

examples/svg/src/main.rs

@@ -31,7 +31,7 @@ impl Tiger {
         ));
 
         let svg = svg(handle).width(Length::Fill).height(Length::Fill).style(
-            |_theme, _status| svg::Appearance {
+            |_theme, _status| svg::Style {
                 color: if self.apply_color_filter {
                     Some(color!(0x0000ff))
                 } else {

examples/toast/src/main.rs

@@ -651,45 +651,33 @@ mod toast {
         }
     }
 
-    fn styled(pair: theme::palette::Pair) -> container::Appearance {
+    fn styled(pair: theme::palette::Pair) -> container::Style {
-        container::Appearance {
+        container::Style {
             background: Some(pair.color.into()),
             text_color: pair.text.into(),
             ..Default::default()
         }
     }
 
-    fn primary(
+    fn primary(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
         styled(palette.primary.weak)
     }
 
-    fn secondary(
+    fn secondary(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
         styled(palette.secondary.weak)
     }
 
-    fn success(
+    fn success(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
         styled(palette.success.weak)
     }
 
-    fn danger(
+    fn danger(theme: &Theme) -> container::Style {
-        theme: &Theme,
-        _status: container::Status,
-    ) -> container::Appearance {
         let palette = theme.extended_palette();
 
         styled(palette.danger.weak)

widget/Cargo.toml

@@ -21,6 +21,7 @@ svg = ["iced_renderer/svg"]
 canvas = ["iced_renderer/geometry"]
 qr_code = ["canvas", "qrcode"]
 wgpu = ["iced_renderer/wgpu"]
+advanced = []
 
 [dependencies]
 iced_renderer.workspace = true

widget/src/button.rs

@@ -49,6 +49,7 @@ use crate::core::{
 pub struct Button<'a, Message, Theme = crate::Theme, Renderer = crate::Renderer>
 where
     Renderer: crate::core::Renderer,
+    Theme: Catalog,
 {
     content: Element<'a, Message, Theme, Renderer>,
     on_press: Option<Message>,
@@ -56,20 +57,18 @@ where
     height: Length,
     padding: Padding,
     clip: bool,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Button<'a, Message, Theme, Renderer>
 where
     Renderer: crate::core::Renderer,
+    Theme: Catalog,
 {
     /// Creates a new [`Button`] with the given content.
     pub fn new(
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         let content = content.into();
         let size = content.as_widget().size_hint();
 
@@ -80,7 +79,7 @@ where
             height: size.height.fluid(),
             padding: DEFAULT_PADDING,
             clip: false,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -119,21 +118,30 @@ where
         self
     }
 
-    /// Sets the style variant of this [`Button`].
-    pub fn style(
-        mut self,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
-    ) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
     /// Sets whether the contents of the [`Button`] should be clipped on
     /// overflow.
     pub fn clip(mut self, clip: bool) -> Self {
         self.clip = clip;
         self
     }
+
+    /// Sets the style of the [`Button`].
+    #[must_use]
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Button`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
@@ -146,6 +154,7 @@ impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
 where
     Message: 'a + Clone,
     Renderer: 'a + crate::core::Renderer,
+    Theme: Catalog,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<State>()
@@ -304,19 +313,19 @@ where
             Status::Active
         };
 
-        let styling = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
-        if styling.background.is_some()
+        if style.background.is_some()
-            || styling.border.width > 0.0
+            || style.border.width > 0.0
-            || styling.shadow.color.a > 0.0
+            || style.shadow.color.a > 0.0
         {
             renderer.fill_quad(
                 renderer::Quad {
                     bounds,
-                    border: styling.border,
+                    border: style.border,
-                    shadow: styling.shadow,
+                    shadow: style.shadow,
                 },
-                styling
+                style
                     .background
                     .unwrap_or(Background::Color(Color::TRANSPARENT)),
             );
@@ -333,7 +342,7 @@ where
             renderer,
             theme,
             &renderer::Style {
-                text_color: styling.text_color,
+                text_color: style.text_color,
             },
             content_layout,
             cursor,
@@ -378,7 +387,7 @@ impl<'a, Message, Theme, Renderer> From<Button<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: crate::core::Renderer + 'a,
 {
     fn from(button: Button<'a, Message, Theme, Renderer>) -> Self {
@@ -407,9 +416,9 @@ pub enum Status {
     Disabled,
 }
 
-/// The appearance of a button.
+/// The style of a button.
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the button.
     pub background: Option<Background>,
     /// The text [`Color`] of the button.
@@ -420,8 +429,8 @@ pub struct Appearance {
     pub shadow: Shadow,
 }
 
-impl Appearance {
+impl Style {
-    /// Updates the [`Appearance`] with the given [`Background`].
+    /// Updates the [`Style`] with the given [`Background`].
     pub fn with_background(self, background: impl Into<Background>) -> Self {
         Self {
             background: Some(background.into()),
@@ -430,7 +439,7 @@ impl Appearance {
     }
 }
 
-impl std::default::Default for Appearance {
+impl Default for Style {
     fn default() -> Self {
         Self {
             background: None,
@@ -441,41 +450,41 @@ impl std::default::Default for Appearance {
     }
 }
 
-/// The style of a [`Button`].
+/// The theme catalog of a [`Button`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Button`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Button`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Button`].
-    fn default_style(&self, status: Status) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-        primary(self, status)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(primary)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
-    }
-}
-
-impl DefaultStyle for Color {
-    fn default_style(&self, _status: Status) -> Appearance {
-        Appearance::default().with_background(*self)
     }
 }
 
 /// A primary button; denoting a main action.
-pub fn primary(theme: &Theme, status: Status) -> Appearance {
+pub fn primary(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
     let base = styled(palette.primary.strong);
 
     match status {
         Status::Active | Status::Pressed => base,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             background: Some(Background::Color(palette.primary.base.color)),
             ..base
         },
@@ -484,13 +493,13 @@ pub fn primary(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A secondary button; denoting a complementary action.
-pub fn secondary(theme: &Theme, status: Status) -> Appearance {
+pub fn secondary(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
     let base = styled(palette.secondary.base);
 
     match status {
         Status::Active | Status::Pressed => base,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             background: Some(Background::Color(palette.secondary.strong.color)),
             ..base
         },
@@ -499,13 +508,13 @@ pub fn secondary(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A success button; denoting a good outcome.
-pub fn success(theme: &Theme, status: Status) -> Appearance {
+pub fn success(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
     let base = styled(palette.success.base);
 
     match status {
         Status::Active | Status::Pressed => base,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             background: Some(Background::Color(palette.success.strong.color)),
             ..base
         },
@@ -514,13 +523,13 @@ pub fn success(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A danger button; denoting a destructive action.
-pub fn danger(theme: &Theme, status: Status) -> Appearance {
+pub fn danger(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
     let base = styled(palette.danger.base);
 
     match status {
         Status::Active | Status::Pressed => base,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             background: Some(Background::Color(palette.danger.strong.color)),
             ..base
         },
@@ -529,17 +538,17 @@ pub fn danger(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A text button; useful for links.
-pub fn text(theme: &Theme, status: Status) -> Appearance {
+pub fn text(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
-    let base = Appearance {
+    let base = Style {
         text_color: palette.background.base.text,
-        ..Appearance::default()
+        ..Style::default()
     };
 
     match status {
         Status::Active | Status::Pressed => base,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             text_color: palette.background.base.text.scale_alpha(0.8),
             ..base
         },
@@ -547,21 +556,21 @@ pub fn text(theme: &Theme, status: Status) -> Appearance {
     }
 }
 
-fn styled(pair: palette::Pair) -> Appearance {
+fn styled(pair: palette::Pair) -> Style {
-    Appearance {
+    Style {
         background: Some(Background::Color(pair.color)),
         text_color: pair.text,
         border: Border::rounded(2),
-        ..Appearance::default()
+        ..Style::default()
     }
 }
 
-fn disabled(appearance: Appearance) -> Appearance {
+fn disabled(style: Style) -> Style {
-    Appearance {
+    Style {
-        background: appearance
+        background: style
             .background
             .map(|background| background.scale_alpha(0.5)),
-        text_color: appearance.text_color.scale_alpha(0.5),
+        text_color: style.text_color.scale_alpha(0.5),
-        ..appearance
+        ..style
     }
 }

widget/src/checkbox.rs

@@ -39,6 +39,7 @@ pub struct Checkbox<
     Renderer = crate::Renderer,
 > where
     Renderer: text::Renderer,
+    Theme: Catalog,
 {
     is_checked: bool,
     on_toggle: Option<Box<dyn Fn(bool) -> Message + 'a>>,
@@ -51,12 +52,13 @@ pub struct Checkbox<
     text_shaping: text::Shaping,
     font: Option<Renderer::Font>,
     icon: Icon<Renderer::Font>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Checkbox<'a, Message, Theme, Renderer>
 where
     Renderer: text::Renderer,
+    Theme: Catalog,
 {
     /// The default size of a [`Checkbox`].
     const DEFAULT_SIZE: f32 = 16.0;
@@ -69,10 +71,7 @@ where
     /// It expects:
     ///   * the label of the [`Checkbox`]
     ///   * a boolean describing whether the [`Checkbox`] is checked or not
-    pub fn new(label: impl Into<String>, is_checked: bool) -> Self
+    pub fn new(label: impl Into<String>, is_checked: bool) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Checkbox {
             is_checked,
             on_toggle: None,
@@ -91,7 +90,7 @@ where
                 line_height: text::LineHeight::default(),
                 shaping: text::Shaping::Basic,
             },
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -174,11 +173,20 @@ where
     }
 
     /// Sets the style of the [`Checkbox`].
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Checkbox`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -187,6 +195,7 @@ impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Checkbox<'a, Message, Theme, Renderer>
 where
     Renderer: text::Renderer,
+    Theme: Catalog,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<widget::text::State<Renderer::Paragraph>>()
@@ -285,7 +294,7 @@ where
         tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         viewport: &Rectangle,
@@ -304,7 +313,7 @@ where
             Status::Active { is_checked }
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
         {
             let layout = children.next().unwrap();
@@ -313,10 +322,10 @@ where
             renderer.fill_quad(
                 renderer::Quad {
                     bounds,
-                    border: appearance.border,
+                    border: style.border,
                     ..renderer::Quad::default()
                 },
-                appearance.background,
+                style.background,
             );
 
             let Icon {
@@ -341,7 +350,7 @@ where
                         shaping: *shaping,
                     },
                     bounds.center(),
-                    appearance.icon_color,
+                    style.icon_color,
                     *viewport,
                 );
             }
@@ -352,11 +361,11 @@ where
 
             crate::text::draw(
                 renderer,
-                style,
+                defaults,
                 label_layout,
                 tree.state.downcast_ref(),
-                crate::text::Appearance {
+                crate::text::Style {
-                    color: appearance.text_color,
+                    color: style.text_color,
                 },
                 viewport,
             );
@@ -368,7 +377,7 @@ impl<'a, Message, Theme, Renderer> From<Checkbox<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: 'a + Catalog,
     Renderer: 'a + text::Renderer,
 {
     fn from(
@@ -413,9 +422,9 @@ pub enum Status {
     },
 }
 
-/// The appearance of a checkbox.
+/// The style of a checkbox.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the checkbox.
     pub background: Background,
     /// The icon [`Color`] of the checkbox.
@@ -426,29 +435,37 @@ pub struct Appearance {
     pub text_color: Option<Color>,
 }
 
-/// The style of a [`Checkbox`].
+/// The theme catalog of a [`Checkbox`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Checkbox`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Checkbox`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Checkbox`].
-    fn default_style(&self, status: Status) -> Appearance {
+///
-        primary(self, status)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(primary)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// A primary checkbox; denoting a main toggle.
-pub fn primary(theme: &Theme, status: Status) -> Appearance {
+pub fn primary(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     match status {
@@ -474,7 +491,7 @@ pub fn primary(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A secondary checkbox; denoting a complementary toggle.
-pub fn secondary(theme: &Theme, status: Status) -> Appearance {
+pub fn secondary(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     match status {
@@ -500,7 +517,7 @@ pub fn secondary(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A success checkbox; denoting a positive toggle.
-pub fn success(theme: &Theme, status: Status) -> Appearance {
+pub fn success(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     match status {
@@ -526,7 +543,7 @@ pub fn success(theme: &Theme, status: Status) -> Appearance {
 }
 
 /// A danger checkbox; denoting a negaive toggle.
-pub fn danger(theme: &Theme, status: Status) -> Appearance {
+pub fn danger(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     match status {
@@ -556,8 +573,8 @@ fn styled(
     base: palette::Pair,
     accent: palette::Pair,
     is_checked: bool,
-) -> Appearance {
+) -> Style {
-    Appearance {
+    Style {
         background: Background::Color(if is_checked {
             accent.color
         } else {

widget/src/combo_box.rs

@@ -32,6 +32,7 @@ pub struct ComboBox<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     state: &'a State<T>,
@@ -42,7 +43,7 @@ pub struct ComboBox<
     on_option_hovered: Option<Box<dyn Fn(T) -> Message>>,
     on_close: Option<Message>,
     on_input: Option<Box<dyn Fn(String) -> Message>>,
-    menu_style: menu::Style<'a, Theme>,
+    menu_class: <Theme as menu::Catalog>::Class<'a>,
     padding: Padding,
     size: Option<f32>,
 }
@@ -50,6 +51,7 @@ pub struct ComboBox<
 impl<'a, T, Message, Theme, Renderer> ComboBox<'a, T, Message, Theme, Renderer>
 where
     T: std::fmt::Display + Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Creates a new [`ComboBox`] with the given list of options, a placeholder,
@@ -60,18 +62,10 @@ where
         placeholder: &str,
         selection: Option<&T>,
         on_selected: impl Fn(T) -> Message + 'static,
-    ) -> Self
+    ) -> Self {
-    where
+        let text_input = TextInput::new(placeholder, &state.value())
-        Theme: DefaultStyle + 'a,
+            .on_input(TextInputEvent::TextChanged)
-    {
+            .class(Theme::default_input());
-        let style = Theme::default_style();
-
-        let text_input = TextInput::with_style(
-            placeholder,
-            &state.value(),
-            style.text_input,
-        )
-        .on_input(TextInputEvent::TextChanged);
 
         let selection = selection.map(T::to_string).unwrap_or_default();
 
@@ -84,7 +78,7 @@ where
             on_option_hovered: None,
             on_input: None,
             on_close: None,
-            menu_style: style.menu,
+            menu_class: <Theme as Catalog>::default_menu(),
             padding: text_input::DEFAULT_PADDING,
             size: None,
         }
@@ -124,18 +118,6 @@ where
         self
     }
 
-    /// Sets the style of the [`ComboBox`].
-    pub fn style(mut self, style: impl Into<Style<'a, Theme>>) -> Self
-    where
-        Theme: 'a,
-    {
-        let style = style.into();
-
-        self.text_input = self.text_input.style(style.text_input);
-        self.menu_style = style.menu;
-        self
-    }
-
     /// Sets the [`Renderer::Font`] of the [`ComboBox`].
     ///
     /// [`Renderer::Font`]: text::Renderer
@@ -173,6 +155,55 @@ where
             ..self
         }
     }
+
+    /// Sets the style of the input of the [`ComboBox`].
+    #[must_use]
+    pub fn input_style(
+        mut self,
+        style: impl Fn(&Theme, text_input::Status) -> text_input::Style + 'a,
+    ) -> Self
+    where
+        <Theme as text_input::Catalog>::Class<'a>:
+            From<text_input::StyleFn<'a, Theme>>,
+    {
+        self.text_input = self.text_input.style(style);
+        self
+    }
+
+    /// Sets the style of the menu of the [`ComboBox`].
+    #[must_use]
+    pub fn menu_style(
+        mut self,
+        style: impl Fn(&Theme) -> menu::Style + 'a,
+    ) -> Self
+    where
+        <Theme as menu::Catalog>::Class<'a>: From<menu::StyleFn<'a, Theme>>,
+    {
+        self.menu_class = (Box::new(style) as menu::StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the input of the [`ComboBox`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn input_class(
+        mut self,
+        class: impl Into<<Theme as text_input::Catalog>::Class<'a>>,
+    ) -> Self {
+        self.text_input = self.text_input.class(class);
+        self
+    }
+
+    /// Sets the style class of the menu of the [`ComboBox`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn menu_class(
+        mut self,
+        class: impl Into<<Theme as menu::Catalog>::Class<'a>>,
+    ) -> Self {
+        self.menu_class = class.into();
+        self
+    }
 }
 
 /// The local state of a [`ComboBox`].
@@ -296,6 +327,7 @@ impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
 where
     T: Display + Clone + 'static,
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn size(&self) -> Size<Length> {
@@ -686,7 +718,7 @@ where
                     (self.on_selected)(x)
                 },
                 self.on_option_hovered.as_deref(),
-                &self.menu_style,
+                &self.menu_class,
             )
             .width(bounds.width)
             .padding(self.padding);
@@ -712,7 +744,7 @@ impl<'a, T, Message, Theme, Renderer>
 where
     T: Display + Clone + 'static,
     Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(combo_box: ComboBox<'a, T, Message, Theme, Renderer>) -> Self {
@@ -720,6 +752,21 @@ where
     }
 }
 
+/// The theme catalog of a [`ComboBox`].
+pub trait Catalog: text_input::Catalog + menu::Catalog {
+    /// The default class for the text input of the [`ComboBox`].
+    fn default_input<'a>() -> <Self as text_input::Catalog>::Class<'a> {
+        <Self as text_input::Catalog>::default()
+    }
+
+    /// The default class for the menu of the [`ComboBox`].
+    fn default_menu<'a>() -> <Self as menu::Catalog>::Class<'a> {
+        <Self as menu::Catalog>::default()
+    }
+}
+
+impl Catalog for Theme {}
+
 fn search<'a, T, A>(
     options: impl IntoIterator<Item = T> + 'a,
     option_matchers: impl IntoIterator<Item = &'a A> + 'a,
@@ -762,30 +809,3 @@ where
         })
         .collect()
 }
-
-/// The style of a [`ComboBox`].
-#[allow(missing_debug_implementations)]
-pub struct Style<'a, Theme> {
-    /// The style of the [`TextInput`] of the [`ComboBox`].
-    pub text_input: text_input::Style<'a, Theme>,
-
-    /// The style of the [`Menu`] of the [`ComboBox`].
-    ///
-    /// [`Menu`]: menu::Menu
-    pub menu: menu::Style<'a, Theme>,
-}
-
-/// The default style of a [`ComboBox`].
-pub trait DefaultStyle: Sized {
-    /// Returns the default style of a [`ComboBox`].
-    fn default_style() -> Style<'static, Self>;
-}
-
-impl DefaultStyle for Theme {
-    fn default_style() -> Style<'static, Self> {
-        Style {
-            text_input: Box::new(text_input::default),
-            menu: menu::DefaultStyle::default_style(),
-        }
-    }
-}

widget/src/container.rs

@@ -9,8 +9,9 @@ use crate::core::renderer;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::widget::{self, Operation};
 use crate::core::{
-    Background, Border, Clipboard, Color, Element, Layout, Length, Padding,
+    self, Background, Border, Clipboard, Color, Element, Layout, Length,
-    Pixels, Point, Rectangle, Shadow, Shell, Size, Theme, Vector, Widget,
+    Padding, Pixels, Point, Rectangle, Shadow, Shell, Size, Theme, Vector,
+    Widget,
 };
 use crate::runtime::Command;
 
@@ -24,7 +25,8 @@ pub struct Container<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     id: Option<Id>,
     padding: Padding,
@@ -36,27 +38,17 @@ pub struct Container<
     vertical_alignment: alignment::Vertical,
     clip: bool,
     content: Element<'a, Message, Theme, Renderer>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Container<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     /// Creates a [`Container`] with the given content.
     pub fn new(
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
-    ) -> Self
-    where
-        Theme: DefaultStyle + 'a,
-    {
-        Self::with_style(content, Theme::default_style)
-    }
-
-    /// Creates a [`Container`] with the given content and style.
-    pub fn with_style(
-        content: impl Into<Element<'a, Message, Theme, Renderer>>,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
     ) -> Self {
         let content = content.into();
         let size = content.as_widget().size_hint();
@@ -71,7 +63,7 @@ where
             horizontal_alignment: alignment::Horizontal::Left,
             vertical_alignment: alignment::Vertical::Top,
             clip: false,
-            style: Box::new(style),
+            class: Theme::default(),
             content,
         }
     }
@@ -136,27 +128,37 @@ where
         self
     }
 
-    /// Sets the style of the [`Container`].
-    pub fn style(
-        mut self,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
-    ) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
     /// Sets whether the contents of the [`Container`] should be clipped on
     /// overflow.
     pub fn clip(mut self, clip: bool) -> Self {
         self.clip = clip;
         self
     }
+
+    /// Sets the style of the [`Container`].
+    #[must_use]
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Container`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Container<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     fn tag(&self) -> tree::Tag {
         self.content.as_widget().tag()
@@ -272,14 +274,7 @@ where
         viewport: &Rectangle,
     ) {
         let bounds = layout.bounds();
-
+        let style = theme.style(&self.class);
-        let status = if cursor.is_over(bounds) {
-            Status::Hovered
-        } else {
-            Status::Idle
-        };
-
-        let style = (self.style)(theme, status);
 
         if let Some(clipped_viewport) = bounds.intersection(viewport) {
             draw_background(renderer, &style, bounds);
@@ -324,8 +319,8 @@ impl<'a, Message, Theme, Renderer> From<Container<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
-    Renderer: 'a + crate::core::Renderer,
+    Renderer: core::Renderer + 'a,
 {
     fn from(
         column: Container<'a, Message, Theme, Renderer>,
@@ -362,25 +357,25 @@ pub fn layout(
     )
 }
 
-/// Draws the background of a [`Container`] given its [`Appearance`] and its `bounds`.
+/// Draws the background of a [`Container`] given its [`Style`] and its `bounds`.
 pub fn draw_background<Renderer>(
     renderer: &mut Renderer,
-    appearance: &Appearance,
+    style: &Style,
     bounds: Rectangle,
 ) where
-    Renderer: crate::core::Renderer,
+    Renderer: core::Renderer,
 {
-    if appearance.background.is_some()
+    if style.background.is_some()
-        || appearance.border.width > 0.0
+        || style.border.width > 0.0
-        || appearance.shadow.color.a > 0.0
+        || style.shadow.color.a > 0.0
     {
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: appearance.border,
+                border: style.border,
-                shadow: appearance.shadow,
+                shadow: style.shadow,
             },
-            appearance
+            style
                 .background
                 .unwrap_or(Background::Color(Color::TRANSPARENT)),
         );
@@ -502,7 +497,7 @@ pub fn visible_bounds(id: Id) -> Command<Option<Rectangle>> {
 
 /// The appearance of a container.
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Appearance {
+pub struct Style {
     /// The text [`Color`] of the container.
     pub text_color: Option<Color>,
     /// The [`Background`] of the container.
@@ -513,8 +508,8 @@ pub struct Appearance {
     pub shadow: Shadow,
 }
 
-impl Appearance {
+impl Style {
-    /// Updates the border of the [`Appearance`] with the given [`Color`] and `width`.
+    /// Updates the border of the [`Style`] with the given [`Color`] and `width`.
     pub fn with_border(
         self,
         color: impl Into<Color>,
@@ -530,7 +525,7 @@ impl Appearance {
         }
     }
 
-    /// Updates the background of the [`Appearance`].
+    /// Updates the background of the [`Style`].
     pub fn with_background(self, background: impl Into<Background>) -> Self {
         Self {
             background: Some(background.into()),
@@ -539,99 +534,78 @@ impl Appearance {
     }
 }
 
-impl From<Color> for Appearance {
+impl From<Color> for Style {
     fn from(color: Color) -> Self {
         Self::default().with_background(color)
     }
 }
 
-impl From<Gradient> for Appearance {
+impl From<Gradient> for Style {
     fn from(gradient: Gradient) -> Self {
         Self::default().with_background(gradient)
     }
 }
 
-impl From<gradient::Linear> for Appearance {
+impl From<gradient::Linear> for Style {
     fn from(gradient: gradient::Linear) -> Self {
         Self::default().with_background(gradient)
     }
 }
 
-/// The possible status of a [`Container`].
+/// The theme catalog of a [`Container`].
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub trait Catalog {
-pub enum Status {
+    /// The item class of the [`Catalog`].
-    /// The [`Container`] is idle.
+    type Class<'a>;
-    Idle,
+
-    /// The [`Container`] is being hovered.
+    /// The default class produced by the [`Catalog`].
-    Hovered,
+    fn default<'a>() -> Self::Class<'a>;
+
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>) -> Style;
 }
 
-/// The style of a [`Container`].
+/// A styling function for a [`Container`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
 
-/// The default style of a [`Container`].
+impl Catalog for Theme {
-pub trait DefaultStyle {
+    type Class<'a> = StyleFn<'a, Self>;
-    /// Returns the default style of a [`Container`].
-    fn default_style(&self, status: Status) -> Appearance;
-}
 
-impl DefaultStyle for Theme {
+    fn default<'a>() -> Self::Class<'a> {
-    fn default_style(&self, status: Status) -> Appearance {
+        Box::new(transparent)
-        transparent(self, status)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self)
-        *self
-    }
-}
-
-impl DefaultStyle for Color {
-    fn default_style(&self, _status: Status) -> Appearance {
-        Appearance::from(*self)
-    }
-}
-
-impl DefaultStyle for Gradient {
-    fn default_style(&self, _status: Status) -> Appearance {
-        Appearance::from(*self)
-    }
-}
-
-impl DefaultStyle for gradient::Linear {
-    fn default_style(&self, _status: Status) -> Appearance {
-        Appearance::from(*self)
     }
 }
 
 /// A transparent [`Container`].
-pub fn transparent<Theme>(_theme: &Theme, _status: Status) -> Appearance {
+pub fn transparent<Theme>(_theme: &Theme) -> Style {
-    Appearance::default()
+    Style::default()
 }
 
 /// A rounded [`Container`] with a background.
-pub fn rounded_box(theme: &Theme, _status: Status) -> Appearance {
+pub fn rounded_box(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
-    Appearance {
+    Style {
         background: Some(palette.background.weak.color.into()),
         border: Border::rounded(2),
-        ..Appearance::default()
+        ..Style::default()
     }
 }
 
 /// A bordered [`Container`] with a background.
-pub fn bordered_box(theme: &Theme, _status: Status) -> Appearance {
+pub fn bordered_box(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
-    Appearance {
+    Style {
         background: Some(palette.background.weak.color.into()),
         border: Border {
             width: 1.0,
             radius: 0.0.into(),
             color: palette.background.strong.color,
         },
-        ..Appearance::default()
+        ..Style::default()
     }
 }

widget/src/helpers.rs

@@ -7,6 +7,7 @@ use crate::core;
 use crate::core::widget::operation;
 use crate::core::{Element, Length, Pixels};
 use crate::keyed;
+use crate::overlay;
 use crate::pick_list::{self, PickList};
 use crate::progress_bar::{self, ProgressBar};
 use crate::radio::{self, Radio};
@@ -58,7 +59,7 @@ pub fn container<'a, Message, Theme, Renderer>(
     content: impl Into<Element<'a, Message, Theme, Renderer>>,
 ) -> Container<'a, Message, Theme, Renderer>
 where
-    Theme: container::DefaultStyle + 'a,
+    Theme: container::Catalog + 'a,
     Renderer: core::Renderer,
 {
     Container::new(content)
@@ -104,7 +105,7 @@ pub fn scrollable<'a, Message, Theme, Renderer>(
     content: impl Into<Element<'a, Message, Theme, Renderer>>,
 ) -> Scrollable<'a, Message, Theme, Renderer>
 where
-    Theme: scrollable::DefaultStyle + 'a,
+    Theme: scrollable::Catalog + 'a,
     Renderer: core::Renderer,
 {
     Scrollable::new(content)
@@ -117,7 +118,7 @@ pub fn button<'a, Message, Theme, Renderer>(
     content: impl Into<Element<'a, Message, Theme, Renderer>>,
 ) -> Button<'a, Message, Theme, Renderer>
 where
-    Theme: button::DefaultStyle + 'a,
+    Theme: button::Catalog + 'a,
     Renderer: core::Renderer,
 {
     Button::new(content)
@@ -134,7 +135,7 @@ pub fn tooltip<'a, Message, Theme, Renderer>(
     position: tooltip::Position,
 ) -> crate::Tooltip<'a, Message, Theme, Renderer>
 where
-    Theme: container::DefaultStyle + 'a,
+    Theme: container::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     Tooltip::new(content, tooltip, position)
@@ -147,7 +148,7 @@ pub fn text<'a, Theme, Renderer>(
     text: impl ToString,
 ) -> Text<'a, Theme, Renderer>
 where
-    Theme: text::DefaultStyle + 'a,
+    Theme: text::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     Text::new(text.to_string())
@@ -161,7 +162,7 @@ pub fn checkbox<'a, Message, Theme, Renderer>(
     is_checked: bool,
 ) -> Checkbox<'a, Message, Theme, Renderer>
 where
-    Theme: checkbox::DefaultStyle + 'a,
+    Theme: checkbox::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     Checkbox::new(label, is_checked)
@@ -178,7 +179,7 @@ pub fn radio<'a, Message, Theme, Renderer, V>(
 ) -> Radio<'a, Message, Theme, Renderer>
 where
     Message: Clone,
-    Theme: radio::DefaultStyle + 'a,
+    Theme: radio::Catalog + 'a,
     Renderer: core::text::Renderer,
     V: Copy + Eq,
 {
@@ -194,7 +195,7 @@ pub fn toggler<'a, Message, Theme, Renderer>(
     f: impl Fn(bool) -> Message + 'a,
 ) -> Toggler<'a, Message, Theme, Renderer>
 where
-    Theme: toggler::DefaultStyle + 'a,
+    Theme: toggler::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     Toggler::new(label, is_checked, f)
@@ -209,7 +210,7 @@ pub fn text_input<'a, Message, Theme, Renderer>(
 ) -> TextInput<'a, Message, Theme, Renderer>
 where
     Message: Clone,
-    Theme: text_input::DefaultStyle + 'a,
+    Theme: text_input::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     TextInput::new(placeholder, value)
@@ -223,7 +224,7 @@ pub fn text_editor<'a, Message, Theme, Renderer>(
 ) -> TextEditor<'a, core::text::highlighter::PlainText, Message, Theme, Renderer>
 where
     Message: Clone,
-    Theme: text_editor::DefaultStyle + 'a,
+    Theme: text_editor::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     TextEditor::new(content)
@@ -240,7 +241,7 @@ pub fn slider<'a, T, Message, Theme>(
 where
     T: Copy + From<u8> + std::cmp::PartialOrd,
     Message: Clone,
-    Theme: slider::DefaultStyle + 'a,
+    Theme: slider::Catalog + 'a,
 {
     Slider::new(range, value, on_change)
 }
@@ -256,7 +257,7 @@ pub fn vertical_slider<'a, T, Message, Theme>(
 where
     T: Copy + From<u8> + std::cmp::PartialOrd,
     Message: Clone,
-    Theme: vertical_slider::DefaultStyle + 'a,
+    Theme: vertical_slider::Catalog + 'a,
 {
     VerticalSlider::new(range, value, on_change)
 }
@@ -274,7 +275,7 @@ where
     L: Borrow<[T]> + 'a,
     V: Borrow<T> + 'a,
     Message: Clone,
-    Theme: pick_list::DefaultStyle,
+    Theme: pick_list::Catalog + overlay::menu::Catalog,
     Renderer: core::text::Renderer,
 {
     PickList::new(options, selected, on_selected)
@@ -291,7 +292,7 @@ pub fn combo_box<'a, T, Message, Theme, Renderer>(
 ) -> ComboBox<'a, T, Message, Theme, Renderer>
 where
     T: std::fmt::Display + Clone,
-    Theme: combo_box::DefaultStyle + 'a,
+    Theme: combo_box::Catalog + 'a,
     Renderer: core::text::Renderer,
 {
     ComboBox::new(state, placeholder, selection, on_selected)
@@ -318,7 +319,7 @@ pub fn vertical_space() -> Space {
 /// [`Rule`]: crate::Rule
 pub fn horizontal_rule<'a, Theme>(height: impl Into<Pixels>) -> Rule<'a, Theme>
 where
-    Theme: rule::DefaultStyle + 'a,
+    Theme: rule::Catalog + 'a,
 {
     Rule::horizontal(height)
 }
@@ -328,7 +329,7 @@ where
 /// [`Rule`]: crate::Rule
 pub fn vertical_rule<'a, Theme>(width: impl Into<Pixels>) -> Rule<'a, Theme>
 where
-    Theme: rule::DefaultStyle + 'a,
+    Theme: rule::Catalog + 'a,
 {
     Rule::vertical(width)
 }
@@ -345,7 +346,7 @@ pub fn progress_bar<'a, Theme>(
     value: f32,
 ) -> ProgressBar<'a, Theme>
 where
-    Theme: progress_bar::DefaultStyle + 'a,
+    Theme: progress_bar::Catalog + 'a,
 {
     ProgressBar::new(range, value)
 }
@@ -367,7 +368,7 @@ pub fn svg<'a, Theme>(
     handle: impl Into<core::svg::Handle>,
 ) -> crate::Svg<'a, Theme>
 where
-    Theme: crate::svg::DefaultStyle + 'a,
+    Theme: crate::svg::Catalog,
 {
     crate::Svg::new(handle)
 }
@@ -395,7 +396,7 @@ pub fn qr_code<'a, Theme>(
     data: &'a crate::qr_code::Data,
 ) -> crate::QRCode<'a, Theme>
 where
-    Theme: crate::qr_code::DefaultStyle + 'a,
+    Theme: crate::qr_code::Catalog + 'a,
 {
     crate::QRCode::new(data)
 }

widget/src/overlay/menu.rs

@@ -1,5 +1,4 @@
 //! Build and show dropdown menus.
-use crate::container::{self, Container};
 use crate::core::alignment;
 use crate::core::event::{self, Event};
 use crate::core::layout::{self, Layout};
@@ -20,12 +19,15 @@ use crate::scrollable::{self, Scrollable};
 #[allow(missing_debug_implementations)]
 pub struct Menu<
     'a,
+    'b,
     T,
     Message,
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
+    Theme: Catalog,
     Renderer: text::Renderer,
+    'b: 'a,
 {
     state: &'a mut State,
     options: &'a [T],
@@ -38,15 +40,17 @@ pub struct Menu<
     text_line_height: text::LineHeight,
     text_shaping: text::Shaping,
     font: Option<Renderer::Font>,
-    style: &'a Style<'a, Theme>,
+    class: &'a <Theme as Catalog>::Class<'b>,
 }
 
-impl<'a, T, Message, Theme, Renderer> Menu<'a, T, Message, Theme, Renderer>
+impl<'a, 'b, T, Message, Theme, Renderer>
+    Menu<'a, 'b, T, Message, Theme, Renderer>
 where
     T: ToString + Clone,
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
+    'b: 'a,
 {
     /// Creates a new [`Menu`] with the given [`State`], a list of options,
     /// the message to produced when an option is selected, and its [`Style`].
@@ -56,7 +60,7 @@ where
         hovered_option: &'a mut Option<usize>,
         on_selected: impl FnMut(T) -> Message + 'a,
         on_option_hovered: Option<&'a dyn Fn(T) -> Message>,
-        style: &'a Style<'a, Theme>,
+        class: &'a <Theme as Catalog>::Class<'b>,
     ) -> Self {
         Menu {
             state,
@@ -70,7 +74,7 @@ where
             text_line_height: text::LineHeight::default(),
             text_shaping: text::Shaping::Basic,
             font: None,
-            style,
+            class,
         }
     }
 
@@ -153,27 +157,29 @@ impl Default for State {
     }
 }
 
-struct Overlay<'a, Message, Theme, Renderer>
+struct Overlay<'a, 'b, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: crate::core::Renderer,
 {
     position: Point,
     state: &'a mut Tree,
-    container: Container<'a, Message, Theme, Renderer>,
+    list: Scrollable<'a, Message, Theme, Renderer>,
     width: f32,
     target_height: f32,
-    style: &'a Style<'a, Theme>,
+    class: &'a <Theme as Catalog>::Class<'b>,
 }
 
-impl<'a, Message, Theme, Renderer> Overlay<'a, Message, Theme, Renderer>
+impl<'a, 'b, Message, Theme, Renderer> Overlay<'a, 'b, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + scrollable::Catalog + 'a,
     Renderer: text::Renderer + 'a,
+    'b: 'a,
 {
     pub fn new<T>(
         position: Point,
-        menu: Menu<'a, T, Message, Theme, Renderer>,
+        menu: Menu<'a, 'b, T, Message, Theme, Renderer>,
         target_height: f32,
     ) -> Self
     where
@@ -191,46 +197,43 @@ where
             text_size,
             text_line_height,
             text_shaping,
-            style,
+            class,
         } = menu;
 
-        let container = Container::with_style(
+        let list = Scrollable::with_direction(
-            Scrollable::with_direction_and_style(
+            List {
-                List {
+                options,
-                    options,
+                hovered_option,
-                    hovered_option,
+                on_selected,
-                    on_selected,
+                on_option_hovered,
-                    on_option_hovered,
+                font,
-                    font,
+                text_size,
-                    text_size,
+                text_line_height,
-                    text_line_height,
+                text_shaping,
-                    text_shaping,
+                padding,
-                    padding,
+                class,
-                    style: &style.list,
+            },
-                },
+            scrollable::Direction::default(),
-                scrollable::Direction::default(),
-                &style.scrollable,
-            ),
-            container::transparent,
         );
 
-        state.tree.diff(&container as &dyn Widget<_, _, _>);
+        state.tree.diff(&list as &dyn Widget<_, _, _>);
 
         Self {
             position,
             state: &mut state.tree,
-            container,
+            list,
             width,
             target_height,
-            style,
+            class,
         }
     }
 }
 
-impl<'a, Message, Theme, Renderer>
+impl<'a, 'b, Message, Theme, Renderer>
     crate::core::Overlay<Message, Theme, Renderer>
-    for Overlay<'a, Message, Theme, Renderer>
+    for Overlay<'a, 'b, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn layout(&mut self, renderer: &Renderer, bounds: Size) -> layout::Node {
@@ -251,7 +254,7 @@ where
         )
         .width(self.width);
 
-        let node = self.container.layout(self.state, renderer, &limits);
+        let node = self.list.layout(self.state, renderer, &limits);
         let size = node.size();
 
         node.move_to(if space_below > space_above {
@@ -272,7 +275,7 @@ where
     ) -> event::Status {
         let bounds = layout.bounds();
 
-        self.container.on_event(
+        self.list.on_event(
             self.state, event, layout, cursor, renderer, clipboard, shell,
             &bounds,
         )
@@ -285,7 +288,7 @@ where
         viewport: &Rectangle,
         renderer: &Renderer,
     ) -> mouse::Interaction {
-        self.container
+        self.list
             .mouse_interaction(self.state, layout, cursor, viewport, renderer)
     }
 
@@ -293,30 +296,32 @@ where
         &self,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
     ) {
         let bounds = layout.bounds();
 
-        let appearance = (self.style.list)(theme);
+        let style = Catalog::style(theme, self.class);
 
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: appearance.border,
+                border: style.border,
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
-        self.container
+        self.list.draw(
-            .draw(self.state, renderer, theme, style, layout, cursor, &bounds);
+            self.state, renderer, theme, defaults, layout, cursor, &bounds,
+        );
     }
 }
 
-struct List<'a, T, Message, Theme, Renderer>
+struct List<'a, 'b, T, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     options: &'a [T],
@@ -328,13 +333,14 @@ where
     text_line_height: text::LineHeight,
     text_shaping: text::Shaping,
     font: Option<Renderer::Font>,
-    style: &'a dyn Fn(&Theme) -> Appearance,
+    class: &'a <Theme as Catalog>::Class<'b>,
 }
 
-impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
+impl<'a, 'b, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
-    for List<'a, T, Message, Theme, Renderer>
+    for List<'a, 'b, T, Message, Theme, Renderer>
 where
     T: Clone + ToString,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn size(&self) -> Size<Length> {
@@ -477,7 +483,7 @@ where
         _cursor: mouse::Cursor,
         viewport: &Rectangle,
     ) {
-        let appearance = (self.style)(theme);
+        let style = Catalog::style(theme, self.class);
         let bounds = layout.bounds();
 
         let text_size =
@@ -507,14 +513,14 @@ where
                 renderer.fill_quad(
                     renderer::Quad {
                         bounds: Rectangle {
-                            x: bounds.x + appearance.border.width,
+                            x: bounds.x + style.border.width,
-                            width: bounds.width - appearance.border.width * 2.0,
+                            width: bounds.width - style.border.width * 2.0,
                             ..bounds
                         },
-                        border: Border::rounded(appearance.border.radius),
+                        border: Border::rounded(style.border.radius),
                         ..renderer::Quad::default()
                     },
-                    appearance.selected_background,
+                    style.selected_background,
                 );
             }
 
@@ -531,9 +537,9 @@ where
                 },
                 Point::new(bounds.x + self.padding.left, bounds.center_y()),
                 if is_selected {
-                    appearance.selected_text_color
+                    style.selected_text_color
                 } else {
-                    appearance.text_color
+                    style.text_color
                 },
                 *viewport,
             );
@@ -541,23 +547,24 @@ where
     }
 }
 
-impl<'a, T, Message, Theme, Renderer>
+impl<'a, 'b, T, Message, Theme, Renderer>
-    From<List<'a, T, Message, Theme, Renderer>>
+    From<List<'a, 'b, T, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     T: ToString + Clone,
     Message: 'a,
-    Theme: 'a,
+    Theme: 'a + Catalog,
     Renderer: 'a + text::Renderer,
+    'b: 'a,
 {
-    fn from(list: List<'a, T, Message, Theme, Renderer>) -> Self {
+    fn from(list: List<'a, 'b, T, Message, Theme, Renderer>) -> Self {
         Element::new(list)
     }
 }
 
 /// The appearance of a [`Menu`].
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the menu.
     pub background: Background,
     /// The [`Border`] of the menu.
@@ -570,35 +577,43 @@ pub struct Appearance {
     pub selected_background: Background,
 }
 
-/// The style of the different parts of a [`Menu`].
+/// The theme catalog of a [`Menu`].
-#[allow(missing_debug_implementations)]
+pub trait Catalog: scrollable::Catalog {
-pub struct Style<'a, Theme> {
+    /// The item class of the [`Catalog`].
-    /// The style of the list of the [`Menu`].
+    type Class<'a>;
-    pub list: Box<dyn Fn(&Theme) -> Appearance + 'a>,
+
-    /// The style of the [`Scrollable`] of the [`Menu`].
+    /// The default class produced by the [`Catalog`].
-    pub scrollable: scrollable::Style<'a, Theme>,
+    fn default<'a>() -> <Self as Catalog>::Class<'a>;
+
+    /// The default class for the scrollable of the [`Menu`].
+    fn default_scrollable<'a>() -> <Self as scrollable::Catalog>::Class<'a> {
+        <Self as scrollable::Catalog>::default()
+    }
+
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &<Self as Catalog>::Class<'_>) -> Style;
 }
 
-/// The default style of a [`Menu`].
+/// A styling function for a [`Menu`].
-pub trait DefaultStyle: Sized {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
-    /// Returns the default style of a [`Menu`].
-    fn default_style() -> Style<'static, Self>;
-}
 
-impl DefaultStyle for Theme {
+impl Catalog for Theme {
-    fn default_style() -> Style<'static, Self> {
+    type Class<'a> = StyleFn<'a, Self>;
-        Style {
+
-            list: Box::new(default),
+    fn default<'a>() -> StyleFn<'a, Self> {
-            scrollable: Box::new(scrollable::default),
+        Box::new(default)
-        }
+    }
+
+    fn style(&self, class: &StyleFn<'_, Self>) -> Style {
+        class(self)
     }
 }
 
 /// The default style of the list of a [`Menu`].
-pub fn default(theme: &Theme) -> Appearance {
+pub fn default(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
-    Appearance {
+    Style {
         background: palette.background.weak.color.into(),
         border: Border {
             width: 1.0,

widget/src/pane_grid.rs

@@ -30,6 +30,7 @@ pub use split::Split;
 pub use state::State;
 pub use title_bar::TitleBar;
 
+use crate::container;
 use crate::core::event::{self, Event};
 use crate::core::layout;
 use crate::core::mouse;
@@ -39,8 +40,8 @@ use crate::core::touch;
 use crate::core::widget;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::{
-    Background, Border, Clipboard, Color, Element, Layout, Length, Pixels,
+    self, Background, Border, Clipboard, Color, Element, Layout, Length,
-    Point, Rectangle, Shell, Size, Theme, Vector, Widget,
+    Pixels, Point, Rectangle, Shell, Size, Theme, Vector, Widget,
 };
 
 const DRAG_DEADBAND_DISTANCE: f32 = 10.0;
@@ -101,7 +102,8 @@ pub struct PaneGrid<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     contents: Contents<'a, Content<'a, Message, Theme, Renderer>>,
     width: Length,
@@ -110,12 +112,13 @@ pub struct PaneGrid<
     on_click: Option<Box<dyn Fn(Pane) -> Message + 'a>>,
     on_drag: Option<Box<dyn Fn(DragEvent) -> Message + 'a>>,
     on_resize: Option<(f32, Box<dyn Fn(ResizeEvent) -> Message + 'a>)>,
-    style: Style<'a, Theme>,
+    class: <Theme as Catalog>::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> PaneGrid<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     /// Creates a [`PaneGrid`] with the given [`State`] and view function.
     ///
@@ -124,10 +127,7 @@ where
     pub fn new<T>(
         state: &'a State<T>,
         view: impl Fn(Pane, &'a T, bool) -> Content<'a, Message, Theme, Renderer>,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         let contents = if let Some((pane, pane_state)) =
             state.maximized.and_then(|pane| {
                 state.panes.get(&pane).map(|pane_state| (pane, pane_state))
@@ -158,7 +158,7 @@ where
             on_click: None,
             on_drag: None,
             on_resize: None,
-            style: Box::new(Theme::default_style),
+            class: <Theme as Catalog>::default(),
         }
     }
 
@@ -218,8 +218,23 @@ where
     }
 
     /// Sets the style of the [`PaneGrid`].
-    pub fn style(mut self, style: impl Fn(&Theme) -> Appearance + 'a) -> Self {
+    #[must_use]
-        self.style = Box::new(style);
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        <Theme as Catalog>::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`PaneGrid`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(
+        mut self,
+        class: impl Into<<Theme as Catalog>::Class<'a>>,
+    ) -> Self {
+        self.class = class.into();
         self
     }
 
@@ -233,7 +248,8 @@ where
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for PaneGrid<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<state::Action>()
@@ -596,7 +612,7 @@ where
         tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         viewport: &Rectangle,
@@ -677,7 +693,7 @@ where
             None
         };
 
-        let appearance = (self.style)(theme);
+        let style = Catalog::style(theme, &self.class);
 
         for ((id, (content, tree)), pane_layout) in
             contents.zip(layout.children())
@@ -692,7 +708,7 @@ where
                         tree,
                         renderer,
                         theme,
-                        style,
+                        defaults,
                         pane_layout,
                         pane_cursor,
                         viewport,
@@ -710,10 +726,10 @@ where
                             renderer.fill_quad(
                                 renderer::Quad {
                                     bounds,
-                                    border: appearance.hovered_region.border,
+                                    border: style.hovered_region.border,
                                     ..renderer::Quad::default()
                                 },
-                                appearance.hovered_region.background,
+                                style.hovered_region.background,
                             );
                         }
                     }
@@ -723,7 +739,7 @@ where
                         tree,
                         renderer,
                         theme,
-                        style,
+                        defaults,
                         pane_layout,
                         pane_cursor,
                         viewport,
@@ -738,10 +754,10 @@ where
             renderer.fill_quad(
                 renderer::Quad {
                     bounds,
-                    border: appearance.hovered_region.border,
+                    border: style.hovered_region.border,
                     ..renderer::Quad::default()
                 },
-                appearance.hovered_region.background,
+                style.hovered_region.background,
             );
         }
 
@@ -759,7 +775,7 @@ where
                             tree,
                             renderer,
                             theme,
-                            style,
+                            defaults,
                             layout,
                             pane_cursor,
                             viewport,
@@ -772,9 +788,9 @@ where
         if picked_pane.is_none() {
             if let Some((axis, split_region, is_picked)) = picked_split {
                 let highlight = if is_picked {
-                    appearance.picked_split
+                    style.picked_split
                 } else {
-                    appearance.hovered_split
+                    style.hovered_split
                 };
 
                 renderer.fill_quad(
@@ -832,8 +848,8 @@ impl<'a, Message, Theme, Renderer> From<PaneGrid<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
-    Renderer: crate::core::Renderer + 'a,
+    Renderer: core::Renderer + 'a,
 {
     fn from(
         pane_grid: PaneGrid<'a, Message, Theme, Renderer>,
@@ -1116,7 +1132,7 @@ impl<'a, T> Contents<'a, T> {
 
 /// The appearance of a [`PaneGrid`].
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub struct Appearance {
+pub struct Style {
     /// The appearance of a hovered region highlight.
     pub hovered_region: Highlight,
     /// The appearance of a picked split.
@@ -1145,32 +1161,40 @@ pub struct Line {
     pub width: f32,
 }
 
-/// The style of a [`PaneGrid`].
+/// The theme catalog of a [`PaneGrid`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme) -> Appearance + 'a>;
+pub trait Catalog: container::Catalog {
+    /// The item class of this [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`PaneGrid`].
+    /// The default class produced by this [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> <Self as Catalog>::Class<'a>;
-    /// Returns the default style of a [`PaneGrid`].
+
-    fn default_style(&self) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &<Self as Catalog>::Class<'_>) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`PaneGrid`].
-    fn default_style(&self) -> Appearance {
+///
-        default(self)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> StyleFn<'a, Self> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &StyleFn<'_, Self>) -> Style {
-    fn default_style(&self) -> Appearance {
+        class(self)
-        *self
     }
 }
 
 /// The default style of a [`PaneGrid`].
-pub fn default(theme: &Theme) -> Appearance {
+pub fn default(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
-    Appearance {
+    Style {
         hovered_region: Highlight {
             background: Background::Color(Color {
                 a: 0.5,

widget/src/pane_grid/content.rs

@@ -6,7 +6,7 @@ use crate::core::overlay;
 use crate::core::renderer;
 use crate::core::widget::{self, Tree};
 use crate::core::{
-    Clipboard, Element, Layout, Point, Rectangle, Shell, Size, Vector,
+    self, Clipboard, Element, Layout, Point, Rectangle, Shell, Size, Vector,
 };
 use crate::pane_grid::{Draggable, TitleBar};
 
@@ -20,30 +20,29 @@ pub struct Content<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     title_bar: Option<TitleBar<'a, Message, Theme, Renderer>>,
     body: Element<'a, Message, Theme, Renderer>,
-    style: container::Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Content<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     /// Creates a new [`Content`] with the provided body.
-    pub fn new(body: impl Into<Element<'a, Message, Theme, Renderer>>) -> Self
+    pub fn new(body: impl Into<Element<'a, Message, Theme, Renderer>>) -> Self {
-    where
-        Theme: container::DefaultStyle + 'a,
-    {
         Self {
             title_bar: None,
             body: body.into(),
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
-    /// Sets the [`TitleBar`] of this [`Content`].
+    /// Sets the [`TitleBar`] of the [`Content`].
     pub fn title_bar(
         mut self,
         title_bar: TitleBar<'a, Message, Theme, Renderer>,
@@ -53,18 +52,31 @@ where
     }
 
     /// Sets the style of the [`Content`].
+    #[must_use]
     pub fn style(
         mut self,
-        style: impl Fn(&Theme, container::Status) -> container::Appearance + 'a,
+        style: impl Fn(&Theme) -> container::Style + 'a,
-    ) -> Self {
+    ) -> Self
-        self.style = Box::new(style);
+    where
+        Theme::Class<'a>: From<container::StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as container::StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Content`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
 
 impl<'a, Message, Theme, Renderer> Content<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     pub(super) fn state(&self) -> Tree {
         let children = if let Some(title_bar) = self.title_bar.as_ref() {
@@ -93,7 +105,7 @@ where
 
     /// Draws the [`Content`] with the provided [`Renderer`] and [`Layout`].
     ///
-    /// [`Renderer`]: crate::core::Renderer
+    /// [`Renderer`]: core::Renderer
     pub fn draw(
         &self,
         tree: &Tree,
@@ -107,15 +119,7 @@ where
         let bounds = layout.bounds();
 
         {
-            let style = {
+            let style = theme.style(&self.class);
-                let status = if cursor.is_over(bounds) {
-                    container::Status::Hovered
-                } else {
-                    container::Status::Idle
-                };
-
-                (self.style)(theme, status)
-            };
 
             container::draw_background(renderer, &style, bounds);
         }
@@ -381,7 +385,8 @@ where
 impl<'a, Message, Theme, Renderer> Draggable
     for &Content<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     fn can_be_dragged_at(
         &self,
@@ -403,8 +408,8 @@ impl<'a, T, Message, Theme, Renderer> From<T>
     for Content<'a, Message, Theme, Renderer>
 where
     T: Into<Element<'a, Message, Theme, Renderer>>,
-    Theme: container::DefaultStyle + 'a,
+    Theme: container::Catalog + 'a,
-    Renderer: crate::core::Renderer,
+    Renderer: core::Renderer,
 {
     fn from(element: T) -> Self {
         Self::new(element)

widget/src/pane_grid/title_bar.rs

@@ -6,7 +6,8 @@ use crate::core::overlay;
 use crate::core::renderer;
 use crate::core::widget::{self, Tree};
 use crate::core::{
-    Clipboard, Element, Layout, Padding, Point, Rectangle, Shell, Size, Vector,
+    self, Clipboard, Element, Layout, Padding, Point, Rectangle, Shell, Size,
+    Vector,
 };
 
 /// The title bar of a [`Pane`].
@@ -19,32 +20,31 @@ pub struct TitleBar<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     content: Element<'a, Message, Theme, Renderer>,
     controls: Option<Element<'a, Message, Theme, Renderer>>,
     padding: Padding,
     always_show_controls: bool,
-    style: container::Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> TitleBar<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     /// Creates a new [`TitleBar`] with the given content.
     pub fn new(
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: container::DefaultStyle + 'a,
-    {
         Self {
             content: content.into(),
             controls: None,
             padding: Padding::ZERO,
             always_show_controls: false,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -63,15 +63,6 @@ where
         self
     }
 
-    /// Sets the style of the [`TitleBar`].
-    pub fn style(
-        mut self,
-        style: impl Fn(&Theme, container::Status) -> container::Appearance + 'a,
-    ) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
     /// Sets whether or not the [`controls`] attached to this [`TitleBar`] are
     /// always visible.
     ///
@@ -84,11 +75,33 @@ where
         self.always_show_controls = true;
         self
     }
+
+    /// Sets the style of the [`TitleBar`].
+    #[must_use]
+    pub fn style(
+        mut self,
+        style: impl Fn(&Theme) -> container::Style + 'a,
+    ) -> Self
+    where
+        Theme::Class<'a>: From<container::StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as container::StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`TitleBar`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 impl<'a, Message, Theme, Renderer> TitleBar<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: container::Catalog,
+    Renderer: core::Renderer,
 {
     pub(super) fn state(&self) -> Tree {
         let children = if let Some(controls) = self.controls.as_ref() {
@@ -117,7 +130,7 @@ where
 
     /// Draws the [`TitleBar`] with the provided [`Renderer`] and [`Layout`].
     ///
-    /// [`Renderer`]: crate::core::Renderer
+    /// [`Renderer`]: core::Renderer
     pub fn draw(
         &self,
         tree: &Tree,
@@ -130,16 +143,7 @@ where
         show_controls: bool,
     ) {
         let bounds = layout.bounds();
-
+        let style = theme.style(&self.class);
-        let style = {
-            let status = if cursor.is_over(bounds) {
-                container::Status::Hovered
-            } else {
-                container::Status::Idle
-            };
-
-            (self.style)(theme, status)
-        };
 
         let inherited_style = renderer::Style {
             text_color: style.text_color.unwrap_or(inherited_style.text_color),

widget/src/pick_list.rs

@@ -32,6 +32,7 @@ pub struct PickList<
     T: ToString + PartialEq + Clone,
     L: Borrow<[T]> + 'a,
     V: Borrow<T> + 'a,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     on_select: Box<dyn Fn(T) -> Message + 'a>,
@@ -47,7 +48,8 @@ pub struct PickList<
     text_shaping: text::Shaping,
     font: Option<Renderer::Font>,
     handle: Handle<Renderer::Font>,
-    style: Style<'a, Theme>,
+    class: <Theme as Catalog>::Class<'a>,
+    menu_class: <Theme as menu::Catalog>::Class<'a>,
 }
 
 impl<'a, T, L, V, Message, Theme, Renderer>
@@ -57,6 +59,7 @@ where
     L: Borrow<[T]> + 'a,
     V: Borrow<T> + 'a,
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Creates a new [`PickList`] with the given list of options, the current
@@ -65,10 +68,7 @@ where
         options: L,
         selected: Option<V>,
         on_select: impl Fn(T) -> Message + 'a,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: DefaultStyle,
-    {
         Self {
             on_select: Box::new(on_select),
             on_open: None,
@@ -83,7 +83,8 @@ where
             text_shaping: text::Shaping::Basic,
             font: None,
             handle: Handle::default(),
-            style: Theme::default_style(),
+            class: <Theme as Catalog>::default(),
+            menu_class: <Theme as Catalog>::default_menu(),
         }
     }
 
@@ -151,8 +152,23 @@ where
     }
 
     /// Sets the style of the [`PickList`].
-    pub fn style(mut self, style: impl Into<Style<'a, Theme>>) -> Self {
+    #[must_use]
-        self.style = style.into();
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
+    where
+        <Theme as Catalog>::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`PickList`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(
+        mut self,
+        class: impl Into<<Theme as Catalog>::Class<'a>>,
+    ) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -164,6 +180,7 @@ where
     L: Borrow<[T]>,
     V: Borrow<T>,
     Message: Clone + 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn tag(&self) -> tree::Tag {
@@ -409,15 +426,15 @@ where
             Status::Active
         };
 
-        let appearance = (self.style.field)(theme, status);
+        let style = Catalog::style(theme, &self.class, status);
 
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: appearance.border,
+                border: style.border,
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
         let handle = match &self.handle {
@@ -478,7 +495,7 @@ where
                     bounds.x + bounds.width - self.padding.right,
                     bounds.center_y(),
                 ),
-                appearance.handle_color,
+                style.handle_color,
                 *viewport,
             );
         }
@@ -505,9 +522,9 @@ where
                 },
                 Point::new(bounds.x + self.padding.left, bounds.center_y()),
                 if is_selected {
-                    appearance.text_color
+                    style.text_color
                 } else {
-                    appearance.placeholder_color
+                    style.placeholder_color
                 },
                 *viewport,
             );
@@ -539,7 +556,7 @@ where
                     (on_select)(option)
                 },
                 None,
-                &self.style.menu,
+                &self.menu_class,
             )
             .width(bounds.width)
             .padding(self.padding)
@@ -565,7 +582,7 @@ where
     L: Borrow<[T]> + 'a,
     V: Borrow<T> + 'a,
     Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(
@@ -662,7 +679,7 @@ pub enum Status {
 
 /// The appearance of a pick list.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The text [`Color`] of the pick list.
     pub text_color: Color,
     /// The placeholder [`Color`] of the pick list.
@@ -675,36 +692,49 @@ pub struct Appearance {
     pub border: Border,
 }
 
-/// The styles of the different parts of a [`PickList`].
+/// The theme catalog of a [`PickList`].
-#[allow(missing_debug_implementations)]
+pub trait Catalog: menu::Catalog {
-pub struct Style<'a, Theme> {
+    /// The item class of the [`Catalog`].
-    /// The style of the [`PickList`] itself.
+    type Class<'a>;
-    pub field: Box<dyn Fn(&Theme, Status) -> Appearance + 'a>,
 
-    /// The style of the [`Menu`] of the pick list.
+    /// The default class produced by the [`Catalog`].
-    pub menu: menu::Style<'a, Theme>,
+    fn default<'a>() -> <Self as Catalog>::Class<'a>;
+
+    /// The default class for the menu of the [`PickList`].
+    fn default_menu<'a>() -> <Self as menu::Catalog>::Class<'a> {
+        <Self as menu::Catalog>::default()
+    }
+
+    /// The [`Style`] of a class with the given status.
+    fn style(
+        &self,
+        class: &<Self as Catalog>::Class<'_>,
+        status: Status,
+    ) -> Style;
 }
 
-/// The default style of a [`PickList`].
+/// A styling function for a [`PickList`].
-pub trait DefaultStyle: Sized {
+///
-    /// Returns the default style of a [`PickList`].
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
-    fn default_style() -> Style<'static, Self>;
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-}
 
-impl DefaultStyle for Theme {
+impl Catalog for Theme {
-    fn default_style() -> Style<'static, Self> {
+    type Class<'a> = StyleFn<'a, Self>;
-        Style {
+
-            field: Box::new(default),
+    fn default<'a>() -> StyleFn<'a, Self> {
-            menu: menu::DefaultStyle::default_style(),
+        Box::new(default)
-        }
+    }
+
+    fn style(&self, class: &StyleFn<'_, Self>, status: Status) -> Style {
+        class(self, status)
     }
 }
 
 /// The default style of the field of a [`PickList`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
-    let active = Appearance {
+    let active = Style {
         text_color: palette.background.weak.text,
         background: palette.background.weak.color.into(),
         placeholder_color: palette.background.strong.color,
@@ -718,7 +748,7 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
 
     match status {
         Status::Active => active,
-        Status::Hovered | Status::Opened => Appearance {
+        Status::Hovered | Status::Opened => Style {
             border: Border {
                 color: palette.primary.strong.color,
                 ..active.border

widget/src/progress_bar.rs

@@ -4,7 +4,8 @@ use crate::core::mouse;
 use crate::core::renderer;
 use crate::core::widget::Tree;
 use crate::core::{
-    Background, Border, Element, Layout, Length, Rectangle, Size, Theme, Widget,
+    self, Background, Border, Element, Layout, Length, Rectangle, Size, Theme,
+    Widget,
 };
 
 use std::ops::RangeInclusive;
@@ -22,15 +23,21 @@ use std::ops::RangeInclusive;
 ///
 /// ![Progress bar drawn with `iced_wgpu`](https://user-images.githubusercontent.com/18618951/71662391-a316c200-2d51-11ea-9cef-52758cab85e3.png)
 #[allow(missing_debug_implementations)]
-pub struct ProgressBar<'a, Theme = crate::Theme> {
+pub struct ProgressBar<'a, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     range: RangeInclusive<f32>,
     value: f32,
     width: Length,
     height: Option<Length>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
-impl<'a, Theme> ProgressBar<'a, Theme> {
+impl<'a, Theme> ProgressBar<'a, Theme>
+where
+    Theme: Catalog,
+{
     /// The default height of a [`ProgressBar`].
     pub const DEFAULT_HEIGHT: f32 = 30.0;
 
@@ -39,16 +46,13 @@ impl<'a, Theme> ProgressBar<'a, Theme> {
     /// It expects:
     ///   * an inclusive range of possible values
     ///   * the current value of the [`ProgressBar`]
-    pub fn new(range: RangeInclusive<f32>, value: f32) -> Self
+    pub fn new(range: RangeInclusive<f32>, value: f32) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         ProgressBar {
             value: value.clamp(*range.start(), *range.end()),
             range,
             width: Length::Fill,
             height: None,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -65,8 +69,20 @@ impl<'a, Theme> ProgressBar<'a, Theme> {
     }
 
     /// Sets the style of the [`ProgressBar`].
-    pub fn style(mut self, style: impl Fn(&Theme) -> Appearance + 'a) -> Self {
+    #[must_use]
-        self.style = Box::new(style);
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`ProgressBar`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -74,7 +90,8 @@ impl<'a, Theme> ProgressBar<'a, Theme> {
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for ProgressBar<'a, Theme>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     fn size(&self) -> Size<Length> {
         Size {
@@ -116,15 +133,15 @@ where
                 / (range_end - range_start)
         };
 
-        let appearance = (self.style)(theme);
+        let style = theme.style(&self.class);
 
         renderer.fill_quad(
             renderer::Quad {
                 bounds: Rectangle { ..bounds },
-                border: appearance.border,
+                border: style.border,
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
         if active_progress_width > 0.0 {
@@ -134,10 +151,10 @@ where
                         width: active_progress_width,
                         ..bounds
                     },
-                    border: Border::rounded(appearance.border.radius),
+                    border: Border::rounded(style.border.radius),
                     ..renderer::Quad::default()
                 },
-                appearance.bar,
+                style.bar,
             );
         }
     }
@@ -147,8 +164,8 @@ impl<'a, Message, Theme, Renderer> From<ProgressBar<'a, Theme>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: 'a + Catalog,
-    Renderer: 'a + crate::core::Renderer,
+    Renderer: 'a + core::Renderer,
 {
     fn from(
         progress_bar: ProgressBar<'a, Theme>,
@@ -159,7 +176,7 @@ where
 
 /// The appearance of a progress bar.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the progress bar.
     pub background: Background,
     /// The [`Background`] of the bar of the progress bar.
@@ -168,29 +185,37 @@ pub struct Appearance {
     pub border: Border,
 }
 
-/// The style of a [`ProgressBar`].
+/// The theme catalog of a [`ProgressBar`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`ProgressBar`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`ProgressBar`].
+
-    fn default_style(&self) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`ProgressBar`].
-    fn default_style(&self) -> Appearance {
+///
-        primary(self)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(primary)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>) -> Style {
-    fn default_style(&self) -> Appearance {
+        class(self)
-        *self
     }
 }
 
 /// The primary style of a [`ProgressBar`].
-pub fn primary(theme: &Theme) -> Appearance {
+pub fn primary(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
     styled(
@@ -200,7 +225,7 @@ pub fn primary(theme: &Theme) -> Appearance {
 }
 
 /// The secondary style of a [`ProgressBar`].
-pub fn secondary(theme: &Theme) -> Appearance {
+pub fn secondary(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
     styled(
@@ -210,14 +235,14 @@ pub fn secondary(theme: &Theme) -> Appearance {
 }
 
 /// The success style of a [`ProgressBar`].
-pub fn success(theme: &Theme) -> Appearance {
+pub fn success(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
     styled(palette.background.strong.color, palette.success.base.color)
 }
 
 /// The danger style of a [`ProgressBar`].
-pub fn danger(theme: &Theme) -> Appearance {
+pub fn danger(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
     styled(palette.background.strong.color, palette.danger.base.color)
@@ -226,8 +251,8 @@ pub fn danger(theme: &Theme) -> Appearance {
 fn styled(
     background: impl Into<Background>,
     bar: impl Into<Background>,
-) -> Appearance {
+) -> Style {
-    Appearance {
+    Style {
         background: background.into(),
         bar: bar.into(),
         border: Border::rounded(2),

widget/src/qr_code.rs

@@ -19,22 +19,25 @@ const QUIET_ZONE: usize = 2;
 /// A type of matrix barcode consisting of squares arranged in a grid which
 /// can be read by an imaging device, such as a camera.
 #[allow(missing_debug_implementations)]
-pub struct QRCode<'a, Theme = crate::Theme> {
+pub struct QRCode<'a, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     data: &'a Data,
     cell_size: u16,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
-impl<'a, Theme> QRCode<'a, Theme> {
+impl<'a, Theme> QRCode<'a, Theme>
+where
+    Theme: Catalog,
+{
     /// Creates a new [`QRCode`] with the provided [`Data`].
-    pub fn new(data: &'a Data) -> Self
+    pub fn new(data: &'a Data) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Self {
             data,
             cell_size: DEFAULT_CELL_SIZE,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -45,14 +48,27 @@ impl<'a, Theme> QRCode<'a, Theme> {
     }
 
     /// Sets the style of the [`QRCode`].
-    pub fn style(mut self, style: impl Fn(&Theme) -> Appearance + 'a) -> Self {
+    #[must_use]
-        self.style = Box::new(style);
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`QRCode`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
 
-impl<'a, Message, Theme> Widget<Message, Theme, Renderer>
+impl<'a, Message, Theme> Widget<Message, Theme, Renderer> for QRCode<'a, Theme>
-    for QRCode<'a, Theme>
+where
+    Theme: Catalog,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<State>()
@@ -96,13 +112,13 @@ impl<'a, Message, Theme> Widget<Message, Theme, Renderer>
         let bounds = layout.bounds();
         let side_length = self.data.width + 2 * QUIET_ZONE;
 
-        let appearance = (self.style)(theme);
+        let style = theme.style(&self.class);
-        let mut last_appearance = state.last_appearance.borrow_mut();
+        let mut last_style = state.last_style.borrow_mut();
 
-        if Some(appearance) != *last_appearance {
+        if Some(style) != *last_style {
             self.data.cache.clear();
 
-            *last_appearance = Some(appearance);
+            *last_style = Some(style);
         }
 
         // Reuse cache if possible
@@ -114,7 +130,7 @@ impl<'a, Message, Theme> Widget<Message, Theme, Renderer>
             frame.fill_rectangle(
                 Point::ORIGIN,
                 Size::new(side_length as f32, side_length as f32),
-                appearance.background,
+                style.background,
             );
 
             // Avoid drawing on the quiet zone
@@ -133,7 +149,7 @@ impl<'a, Message, Theme> Widget<Message, Theme, Renderer>
                     frame.fill_rectangle(
                         Point::new(column as f32, row as f32),
                         Size::UNIT,
-                        appearance.cell,
+                        style.cell,
                     );
                 });
         });
@@ -152,7 +168,7 @@ impl<'a, Message, Theme> Widget<Message, Theme, Renderer>
 impl<'a, Message, Theme> From<QRCode<'a, Theme>>
     for Element<'a, Message, Theme, Renderer>
 where
-    Theme: 'a,
+    Theme: Catalog + 'a,
 {
     fn from(qr_code: QRCode<'a, Theme>) -> Self {
         Self::new(qr_code)
@@ -324,44 +340,50 @@ impl From<qrcode::types::QrError> for Error {
 
 #[derive(Default)]
 struct State {
-    last_appearance: RefCell<Option<Appearance>>,
+    last_style: RefCell<Option<Style>>,
 }
 
 /// The appearance of a QR code.
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub struct Appearance {
+pub struct Style {
     /// The color of the QR code data cells
     pub cell: Color,
     /// The color of the QR code background
     pub background: Color,
 }
 
-/// The style of a [`QRCode`].
+/// The theme catalog of a [`QRCode`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`QRCode`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`QRCode`].
+
-    fn default_style(&self) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`QRCode`].
-    fn default_style(&self) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
-        default(self)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>) -> Style {
-    fn default_style(&self) -> Appearance {
+        class(self)
-        *self
     }
 }
 
 /// The default style of a [`QRCode`].
-pub fn default(theme: &Theme) -> Appearance {
+pub fn default(theme: &Theme) -> Style {
     let palette = theme.palette();
 
-    Appearance {
+    Style {
         cell: palette.text,
         background: palette.background,
     }

widget/src/radio.rs

@@ -69,6 +69,7 @@ use crate::core::{
 #[allow(missing_debug_implementations)]
 pub struct Radio<'a, Message, Theme = crate::Theme, Renderer = crate::Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     is_selected: bool,
@@ -81,12 +82,13 @@ where
     text_line_height: text::LineHeight,
     text_shaping: text::Shaping,
     font: Option<Renderer::Font>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Radio<'a, Message, Theme, Renderer>
 where
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// The default size of a [`Radio`] button.
@@ -110,7 +112,6 @@ where
         f: F,
     ) -> Self
     where
-        Theme: DefaultStyle + 'a,
         V: Eq + Copy,
         F: FnOnce(V) -> Message,
     {
@@ -125,7 +126,7 @@ where
             text_line_height: text::LineHeight::default(),
             text_shaping: text::Shaping::Basic,
             font: None,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -175,11 +176,20 @@ where
     }
 
     /// Sets the style of the [`Radio`] button.
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Radio`] button.
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -188,6 +198,7 @@ impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Radio<'a, Message, Theme, Renderer>
 where
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn tag(&self) -> tree::Tag {
@@ -284,7 +295,7 @@ where
         tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         viewport: &Rectangle,
@@ -300,7 +311,7 @@ where
             Status::Active { is_selected }
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
         {
             let layout = children.next().unwrap();
@@ -314,12 +325,12 @@ where
                     bounds,
                     border: Border {
                         radius: (size / 2.0).into(),
-                        width: appearance.border_width,
+                        width: style.border_width,
-                        color: appearance.border_color,
+                        color: style.border_color,
                     },
                     ..renderer::Quad::default()
                 },
-                appearance.background,
+                style.background,
             );
 
             if self.is_selected {
@@ -334,7 +345,7 @@ where
                         border: Border::rounded(dot_size / 2.0),
                         ..renderer::Quad::default()
                     },
-                    appearance.dot_color,
+                    style.dot_color,
                 );
             }
         }
@@ -344,11 +355,11 @@ where
 
             crate::text::draw(
                 renderer,
-                style,
+                defaults,
                 label_layout,
                 tree.state.downcast_ref(),
-                crate::text::Appearance {
+                crate::text::Style {
-                    color: appearance.text_color,
+                    color: style.text_color,
                 },
                 viewport,
             );
@@ -360,7 +371,7 @@ impl<'a, Message, Theme, Renderer> From<Radio<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a + Clone,
-    Theme: 'a,
+    Theme: 'a + Catalog,
     Renderer: 'a + text::Renderer,
 {
     fn from(
@@ -387,7 +398,7 @@ pub enum Status {
 
 /// The appearance of a radio button.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the radio button.
     pub background: Background,
     /// The [`Color`] of the dot of the radio button.
@@ -400,32 +411,38 @@ pub struct Appearance {
     pub text_color: Option<Color>,
 }
 
-/// The style of a [`Radio`] button.
+/// The theme catalog of a [`Radio`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Radio`] button.
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Radio`] button.
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Radio`].
-    fn default_style(&self, status: Status) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-        default(self, status)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`Radio`] button.
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
-    let active = Appearance {
+    let active = Style {
         background: Color::TRANSPARENT.into(),
         dot_color: palette.primary.strong.color,
         border_width: 1.0,
@@ -435,7 +452,7 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
 
     match status {
         Status::Active { .. } => active,
-        Status::Hovered { .. } => Appearance {
+        Status::Hovered { .. } => Style {
             dot_color: palette.primary.strong.color,
             background: palette.primary.weak.color.into(),
             ..active

widget/src/rule.rs

@@ -1,4 +1,5 @@
 //! Display a horizontal or vertical rule for dividing content.
+use crate::core;
 use crate::core::border::{self, Border};
 use crate::core::layout;
 use crate::core::mouse;
@@ -10,43 +11,55 @@ use crate::core::{
 
 /// Display a horizontal or vertical rule for dividing content.
 #[allow(missing_debug_implementations)]
-pub struct Rule<'a, Theme = crate::Theme> {
+pub struct Rule<'a, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     width: Length,
     height: Length,
     is_horizontal: bool,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
-impl<'a, Theme> Rule<'a, Theme> {
+impl<'a, Theme> Rule<'a, Theme>
+where
+    Theme: Catalog,
+{
     /// Creates a horizontal [`Rule`] with the given height.
-    pub fn horizontal(height: impl Into<Pixels>) -> Self
+    pub fn horizontal(height: impl Into<Pixels>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Rule {
             width: Length::Fill,
             height: Length::Fixed(height.into().0),
             is_horizontal: true,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
     /// Creates a vertical [`Rule`] with the given width.
-    pub fn vertical(width: impl Into<Pixels>) -> Self
+    pub fn vertical(width: impl Into<Pixels>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Rule {
             width: Length::Fixed(width.into().0),
             height: Length::Fill,
             is_horizontal: false,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
     /// Sets the style of the [`Rule`].
-    pub fn style(mut self, style: impl Fn(&Theme) -> Appearance + 'a) -> Self {
+    #[must_use]
-        self.style = Box::new(style);
+    pub fn style(mut self, style: impl Fn(&Theme) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Rule`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -54,7 +67,8 @@ impl<'a, Theme> Rule<'a, Theme> {
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Rule<'a, Theme>
 where
-    Renderer: crate::core::Renderer,
+    Renderer: core::Renderer,
+    Theme: Catalog,
 {
     fn size(&self) -> Size<Length> {
         Size {
@@ -83,35 +97,34 @@ where
         _viewport: &Rectangle,
     ) {
         let bounds = layout.bounds();
-        let appearance = (self.style)(theme);
+        let style = theme.style(&self.class);
 
         let bounds = if self.is_horizontal {
             let line_y = (bounds.y + (bounds.height / 2.0)
-                - (appearance.width as f32 / 2.0))
+                - (style.width as f32 / 2.0))
                 .round();
 
-            let (offset, line_width) = appearance.fill_mode.fill(bounds.width);
+            let (offset, line_width) = style.fill_mode.fill(bounds.width);
             let line_x = bounds.x + offset;
 
             Rectangle {
                 x: line_x,
                 y: line_y,
                 width: line_width,
-                height: appearance.width as f32,
+                height: style.width as f32,
             }
         } else {
             let line_x = (bounds.x + (bounds.width / 2.0)
-                - (appearance.width as f32 / 2.0))
+                - (style.width as f32 / 2.0))
                 .round();
 
-            let (offset, line_height) =
+            let (offset, line_height) = style.fill_mode.fill(bounds.height);
-                appearance.fill_mode.fill(bounds.height);
             let line_y = bounds.y + offset;
 
             Rectangle {
                 x: line_x,
                 y: line_y,
-                width: appearance.width as f32,
+                width: style.width as f32,
                 height: line_height,
             }
         };
@@ -119,10 +132,10 @@ where
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: Border::rounded(appearance.radius),
+                border: Border::rounded(style.radius),
                 ..renderer::Quad::default()
             },
-            appearance.color,
+            style.color,
         );
     }
 }
@@ -131,8 +144,8 @@ impl<'a, Message, Theme, Renderer> From<Rule<'a, Theme>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: 'a + Catalog,
-    Renderer: 'a + crate::core::Renderer,
+    Renderer: 'a + core::Renderer,
 {
     fn from(rule: Rule<'a, Theme>) -> Element<'a, Message, Theme, Renderer> {
         Element::new(rule)
@@ -141,7 +154,7 @@ where
 
 /// The appearance of a rule.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The color of the rule.
     pub color: Color,
     /// The width (thickness) of the rule line.
@@ -216,32 +229,40 @@ impl FillMode {
     }
 }
 
-/// The style of a [`Rule`].
+/// The theme catalog of a [`Rule`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Rule`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Rule`].
+
-    fn default_style(&self) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Rule`].
-    fn default_style(&self) -> Appearance {
+///
-        default(self)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>) -> Style {
-    fn default_style(&self) -> Appearance {
+        class(self)
-        *self
     }
 }
 
 /// The default styling of a [`Rule`].
-pub fn default(theme: &Theme) -> Appearance {
+pub fn default(theme: &Theme) -> Style {
     let palette = theme.extended_palette();
 
-    Appearance {
+    Style {
         color: palette.background.strong.color,
         width: 1,
         radius: 0.0.into(),

widget/src/scrollable.rs

@@ -12,8 +12,8 @@ use crate::core::widget;
 use crate::core::widget::operation::{self, Operation};
 use crate::core::widget::tree::{self, Tree};
 use crate::core::{
-    Background, Border, Clipboard, Color, Element, Layout, Length, Pixels,
+    self, Background, Border, Clipboard, Color, Element, Layout, Length,
-    Point, Rectangle, Shell, Size, Theme, Vector, Widget,
+    Pixels, Point, Rectangle, Shell, Size, Theme, Vector, Widget,
 };
 use crate::runtime::Command;
 
@@ -28,7 +28,8 @@ pub struct Scrollable<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     id: Option<Id>,
     width: Length,
@@ -36,20 +37,18 @@ pub struct Scrollable<
     direction: Direction,
     content: Element<'a, Message, Theme, Renderer>,
     on_scroll: Option<Box<dyn Fn(Viewport) -> Message + 'a>>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Scrollable<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     /// Creates a new vertical [`Scrollable`].
     pub fn new(
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Self::with_direction(content, Direction::default())
     }
 
@@ -57,18 +56,6 @@ where
     pub fn with_direction(
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
         direction: Direction,
-    ) -> Self
-    where
-        Theme: DefaultStyle + 'a,
-    {
-        Self::with_direction_and_style(content, direction, Theme::default_style)
-    }
-
-    /// Creates a new [`Scrollable`] with the given [`Direction`] and style.
-    pub fn with_direction_and_style(
-        content: impl Into<Element<'a, Message, Theme, Renderer>>,
-        direction: Direction,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
     ) -> Self {
         let content = content.into();
 
@@ -91,7 +78,7 @@ where
             direction,
             content,
             on_scroll: None,
-            style: Box::new(style),
+            class: Theme::default(),
         }
     }
 
@@ -121,12 +108,21 @@ where
         self
     }
 
-    /// Sets the style of the [`Scrollable`] .
+    /// Sets the style of this [`Scrollable`].
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Scrollable`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -237,7 +233,8 @@ pub enum Alignment {
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Scrollable<'a, Message, Theme, Renderer>
 where
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<State>()
@@ -651,7 +648,7 @@ where
         tree: &Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         _viewport: &Rectangle,
@@ -701,13 +698,9 @@ where
             Status::Active
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
-        container::draw_background(
+        container::draw_background(renderer, &style.container, layout.bounds());
-            renderer,
-            &appearance.container,
-            layout.bounds(),
-        );
 
         // Draw inner content
         if scrollbars.active() {
@@ -719,7 +712,7 @@ where
                             &tree.children[0],
                             renderer,
                             theme,
-                            style,
+                            defaults,
                             content_layout,
                             cursor,
                             &Rectangle {
@@ -782,7 +775,7 @@ where
                     if let Some(scrollbar) = scrollbars.y {
                         draw_scrollbar(
                             renderer,
-                            appearance.vertical_scrollbar,
+                            style.vertical_scrollbar,
                             &scrollbar,
                         );
                     }
@@ -790,14 +783,14 @@ where
                     if let Some(scrollbar) = scrollbars.x {
                         draw_scrollbar(
                             renderer,
-                            appearance.horizontal_scrollbar,
+                            style.horizontal_scrollbar,
                             &scrollbar,
                         );
                     }
 
                     if let (Some(x), Some(y)) = (scrollbars.x, scrollbars.y) {
                         let background =
-                            appearance.gap.or(appearance.container.background);
+                            style.gap.or(style.container.background);
 
                         if let Some(background) = background {
                             renderer.fill_quad(
@@ -821,7 +814,7 @@ where
                 &tree.children[0],
                 renderer,
                 theme,
-                style,
+                defaults,
                 content_layout,
                 cursor,
                 &Rectangle {
@@ -916,8 +909,8 @@ impl<'a, Message, Theme, Renderer>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: 'a + Catalog,
-    Renderer: 'a + crate::core::Renderer,
+    Renderer: 'a + core::Renderer,
 {
     fn from(
         text_input: Scrollable<'a, Message, Theme, Renderer>,
@@ -1570,9 +1563,9 @@ pub enum Status {
 
 /// The appearance of a scrolable.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
-    /// The [`container::Appearance`] of a scrollable.
+    /// The [`container::Style`] of a scrollable.
-    pub container: container::Appearance,
+    pub container: container::Style,
     /// The vertical [`Scrollbar`] appearance.
     pub vertical_scrollbar: Scrollbar,
     /// The horizontal [`Scrollbar`] appearance.
@@ -1601,29 +1594,35 @@ pub struct Scroller {
     pub border: Border,
 }
 
-/// The style of a [`Scrollable`].
+/// The theme catalog of a [`Scrollable`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Scrollable`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Scrollable`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Scrollable`].
-    fn default_style(&self, status: Status) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-        default(self, status)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`Scrollable`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     let scrollbar = Scrollbar {
@@ -1636,8 +1635,8 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
     };
 
     match status {
-        Status::Active => Appearance {
+        Status::Active => Style {
-            container: container::Appearance::default(),
+            container: container::Style::default(),
             vertical_scrollbar: scrollbar,
             horizontal_scrollbar: scrollbar,
             gap: None,
@@ -1654,8 +1653,8 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
                 ..scrollbar
             };
 
-            Appearance {
+            Style {
-                container: container::Appearance::default(),
+                container: container::Style::default(),
                 vertical_scrollbar: if is_vertical_scrollbar_hovered {
                     hovered_scrollbar
                 } else {
@@ -1681,8 +1680,8 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
                 ..scrollbar
             };
 
-            Appearance {
+            Style {
-                container: container::Appearance::default(),
+                container: container::Style::default(),
                 vertical_scrollbar: if is_vertical_scrollbar_dragged {
                     dragged_scrollbar
                 } else {

widget/src/slider.rs

@@ -9,7 +9,7 @@ use crate::core::renderer;
 use crate::core::touch;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::{
-    Border, Clipboard, Color, Element, Layout, Length, Pixels, Point,
+    self, Border, Clipboard, Color, Element, Layout, Length, Pixels, Point,
     Rectangle, Shell, Size, Theme, Widget,
 };
 
@@ -39,7 +39,10 @@ use std::ops::RangeInclusive;
 ///
 /// ![Slider drawn by Coffee's renderer](https://github.com/hecrj/coffee/blob/bda9818f823dfcb8a7ad0ff4940b4d4b387b5208/images/ui/slider.png?raw=true)
 #[allow(missing_debug_implementations)]
-pub struct Slider<'a, T, Message, Theme = crate::Theme> {
+pub struct Slider<'a, T, Message, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     range: RangeInclusive<T>,
     step: T,
     shift_step: Option<T>,
@@ -49,13 +52,14 @@ pub struct Slider<'a, T, Message, Theme = crate::Theme> {
     on_release: Option<Message>,
     width: Length,
     height: f32,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, T, Message, Theme> Slider<'a, T, Message, Theme>
 where
     T: Copy + From<u8> + PartialOrd,
     Message: Clone,
+    Theme: Catalog,
 {
     /// The default height of a [`Slider`].
     pub const DEFAULT_HEIGHT: f32 = 16.0;
@@ -70,7 +74,6 @@ where
     ///   `Message`.
     pub fn new<F>(range: RangeInclusive<T>, value: T, on_change: F) -> Self
     where
-        Theme: DefaultStyle + 'a,
         F: 'a + Fn(T) -> Message,
     {
         let value = if value >= *range.start() {
@@ -95,7 +98,7 @@ where
             on_release: None,
             width: Length::Fill,
             height: Self::DEFAULT_HEIGHT,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -130,15 +133,6 @@ where
         self
     }
 
-    /// Sets the style of the [`Slider`].
-    pub fn style(
-        mut self,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
-    ) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
     /// Sets the step size of the [`Slider`].
     pub fn step(mut self, step: impl Into<T>) -> Self {
         self.step = step.into();
@@ -152,6 +146,24 @@ where
         self.shift_step = Some(shift_step.into());
         self
     }
+
+    /// Sets the style of the [`Slider`].
+    #[must_use]
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Slider`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
@@ -159,7 +171,8 @@ impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
 where
     T: Copy + Into<f64> + num_traits::FromPrimitive,
     Message: Clone,
-    Renderer: crate::core::Renderer,
+    Theme: Catalog,
+    Renderer: core::Renderer,
 {
     fn tag(&self) -> tree::Tag {
         tree::Tag::of::<State>()
@@ -349,8 +362,8 @@ where
         let bounds = layout.bounds();
         let is_mouse_over = cursor.is_over(bounds);
 
-        let style = (self.style)(
+        let style = theme.style(
-            theme,
+            &self.class,
             if state.is_dragging {
                 Status::Dragged
             } else if is_mouse_over {
@@ -461,8 +474,8 @@ impl<'a, T, Message, Theme, Renderer> From<Slider<'a, T, Message, Theme>>
 where
     T: Copy + Into<f64> + num_traits::FromPrimitive + 'a,
     Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
-    Renderer: crate::core::Renderer + 'a,
+    Renderer: core::Renderer + 'a,
 {
     fn from(
         slider: Slider<'a, T, Message, Theme>,
@@ -490,15 +503,15 @@ pub enum Status {
 
 /// The appearance of a slider.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The colors of the rail of the slider.
     pub rail: Rail,
     /// The appearance of the [`Handle`] of the slider.
     pub handle: Handle,
 }
 
-impl Appearance {
+impl Style {
-    /// Changes the [`HandleShape`] of the [`Appearance`] to a circle
+    /// Changes the [`HandleShape`] of the [`Style`] to a circle
     /// with the given radius.
     pub fn with_circular_handle(mut self, radius: impl Into<Pixels>) -> Self {
         self.handle.shape = HandleShape::Circle {
@@ -549,29 +562,35 @@ pub enum HandleShape {
     },
 }
 
-/// The style of a [`Slider`].
+/// The theme catalog of a [`Slider`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Slider`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Slider`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Slider`].
-    fn default_style(&self, status: Status) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-        default(self, status)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`Slider`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     let color = match status {
@@ -580,7 +599,7 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
         Status::Dragged => palette.primary.strong.color,
     };
 
-    Appearance {
+    Style {
         rail: Rail {
             colors: (color, palette.secondary.base.color),
             width: 4.0,

widget/src/svg.rs

@@ -20,36 +20,36 @@ pub use crate::core::svg::Handle;
 /// [`Svg`] images can have a considerable rendering cost when resized,
 /// specially when they are complex.
 #[allow(missing_debug_implementations)]
-pub struct Svg<'a, Theme = crate::Theme> {
+pub struct Svg<'a, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     handle: Handle,
     width: Length,
     height: Length,
     content_fit: ContentFit,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
-impl<'a, Theme> Svg<'a, Theme> {
+impl<'a, Theme> Svg<'a, Theme>
+where
+    Theme: Catalog,
+{
     /// Creates a new [`Svg`] from the given [`Handle`].
-    pub fn new(handle: impl Into<Handle>) -> Self
+    pub fn new(handle: impl Into<Handle>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Svg {
             handle: handle.into(),
             width: Length::Fill,
             height: Length::Shrink,
             content_fit: ContentFit::Contain,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
     /// Creates a new [`Svg`] that will display the contents of the file at the
     /// provided path.
     #[must_use]
-    pub fn from_path(path: impl Into<PathBuf>) -> Self
+    pub fn from_path(path: impl Into<PathBuf>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Self::new(Handle::from_path(path))
     }
 
@@ -78,13 +78,21 @@ impl<'a, Theme> Svg<'a, Theme> {
         }
     }
 
-    /// Sets the style variant of this [`Svg`].
+    /// Sets the style of the [`Svg`].
     #[must_use]
-    pub fn style(
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        mut self,
+    where
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-    ) -> Self {
+    {
-        self.style = Box::new(style);
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Svg`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -93,6 +101,7 @@ impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Svg<'a, Theme>
 where
     Renderer: svg::Renderer,
+    Theme: Catalog,
 {
     fn size(&self) -> Size<Length> {
         Size {
@@ -167,11 +176,11 @@ where
                 Status::Idle
             };
 
-            let appearance = (self.style)(theme, status);
+            let style = theme.style(&self.class, status);
 
             renderer.draw_svg(
                 self.handle.clone(),
-                appearance.color,
+                style.color,
                 drawing_bounds + offset,
             );
         };
@@ -189,7 +198,7 @@ where
 impl<'a, Message, Theme, Renderer> From<Svg<'a, Theme>>
     for Element<'a, Message, Theme, Renderer>
 where
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: svg::Renderer + 'a,
 {
     fn from(icon: Svg<'a, Theme>) -> Element<'a, Message, Theme, Renderer> {
@@ -208,7 +217,7 @@ pub enum Status {
 
 /// The appearance of an [`Svg`].
 #[derive(Debug, Clone, Copy, PartialEq, Default)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Color`] filter of an [`Svg`].
     ///
     /// Useful for coloring a symbolic icon.
@@ -217,23 +226,37 @@ pub struct Appearance {
     pub color: Option<Color>,
 }
 
-/// The style of an [`Svg`].
+/// The theme catalog of an [`Svg`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of an [`Svg`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of an [`Svg`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+impl Catalog for Theme {
-    fn default_style(&self, _status: Status) -> Appearance {
+    type Class<'a> = StyleFn<'a, Self>;
-        Appearance::default()
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(|_theme, _status| Style::default())
+    }
+
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
+        class(self, status)
     }
 }
 
-impl DefaultStyle for Appearance {
+/// A styling function for an [`Svg`].
-    fn default_style(&self, _status: Status) -> Appearance {
+///
-        *self
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
+
+impl<'a, Theme> From<Style> for StyleFn<'a, Theme> {
+    fn from(style: Style) -> Self {
+        Box::new(move |_theme, _status| style)
     }
 }

widget/src/text_editor.rs

@@ -32,6 +32,7 @@ pub struct TextEditor<
     Renderer = crate::Renderer,
 > where
     Highlighter: text::Highlighter,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     content: &'a Content<Renderer>,
@@ -41,7 +42,7 @@ pub struct TextEditor<
     width: Length,
     height: Length,
     padding: Padding,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
     on_edit: Option<Box<dyn Fn(Action) -> Message + 'a>>,
     highlighter_settings: Highlighter::Settings,
     highlighter_format: fn(
@@ -53,13 +54,11 @@ pub struct TextEditor<
 impl<'a, Message, Theme, Renderer>
     TextEditor<'a, highlighter::PlainText, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Creates new [`TextEditor`] with the given [`Content`].
-    pub fn new(content: &'a Content<Renderer>) -> Self
+    pub fn new(content: &'a Content<Renderer>) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
         Self {
             content,
             font: None,
@@ -68,7 +67,7 @@ where
             width: Length::Fill,
             height: Length::Shrink,
             padding: Padding::new(5.0),
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
             on_edit: None,
             highlighter_settings: (),
             highlighter_format: |_highlight, _theme| {
@@ -82,6 +81,7 @@ impl<'a, Highlighter, Message, Theme, Renderer>
     TextEditor<'a, Highlighter, Message, Theme, Renderer>
 where
     Highlighter: text::Highlighter,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Sets the height of the [`TextEditor`].
@@ -134,7 +134,7 @@ where
             width: self.width,
             height: self.height,
             padding: self.padding,
-            style: self.style,
+            class: self.class,
             on_edit: self.on_edit,
             highlighter_settings: settings,
             highlighter_format: to_format,
@@ -142,11 +142,20 @@ where
     }
 
     /// Sets the style of the [`TextEditor`].
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`TextEditor`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -309,6 +318,7 @@ impl<'a, Highlighter, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for TextEditor<'a, Highlighter, Message, Theme, Renderer>
 where
     Highlighter: text::Highlighter,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn tag(&self) -> widget::tree::Tag {
@@ -479,7 +489,7 @@ where
         tree: &widget::Tree,
         renderer: &mut Renderer,
         theme: &Theme,
-        style: &renderer::Style,
+        defaults: &renderer::Style,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         viewport: &Rectangle,
@@ -508,22 +518,22 @@ where
             Status::Active
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: appearance.border,
+                border: style.border,
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
         renderer.fill_editor(
             &internal.editor,
             bounds.position()
                 + Vector::new(self.padding.left, self.padding.top),
-            style.text_color,
+            defaults.text_color,
             *viewport,
         );
 
@@ -555,7 +565,7 @@ where
                                 },
                                 ..renderer::Quad::default()
                             },
-                            appearance.value,
+                            style.value,
                         );
                     }
                 }
@@ -568,7 +578,7 @@ where
                                 bounds: range,
                                 ..renderer::Quad::default()
                             },
-                            appearance.selection,
+                            style.selection,
                         );
                     }
                 }
@@ -604,7 +614,7 @@ impl<'a, Highlighter, Message, Theme, Renderer>
 where
     Highlighter: text::Highlighter,
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer,
 {
     fn from(
@@ -796,7 +806,7 @@ pub enum Status {
 
 /// The appearance of a text input.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the text input.
     pub background: Background,
     /// The [`Border`] of the text input.
@@ -811,32 +821,38 @@ pub struct Appearance {
     pub selection: Color,
 }
 
-/// The style of a [`TextEditor`].
+/// The theme catalog of a [`TextEditor`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`TextEditor`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`TextEditor`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`TextEditor`].
-    fn default_style(&self, status: Status) -> Appearance {
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
-        default(self, status)
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`TextEditor`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
-    let active = Appearance {
+    let active = Style {
         background: Background::Color(palette.background.base.color),
         border: Border {
             radius: 2.0.into(),
@@ -851,21 +867,21 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
 
     match status {
         Status::Active => active,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             border: Border {
                 color: palette.background.base.text,
                 ..active.border
             },
             ..active
         },
-        Status::Focused => Appearance {
+        Status::Focused => Style {
             border: Border {
                 color: palette.primary.strong.color,
                 ..active.border
             },
             ..active
         },
-        Status::Disabled => Appearance {
+        Status::Disabled => Style {
             background: Background::Color(palette.background.weak.color),
             value: active.placeholder,
             ..active

widget/src/text_input.rs

@@ -60,6 +60,7 @@ pub struct TextInput<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     id: Option<Id>,
@@ -75,7 +76,7 @@ pub struct TextInput<
     on_paste: Option<Box<dyn Fn(String) -> Message + 'a>>,
     on_submit: Option<Message>,
     icon: Option<Icon<Renderer::Font>>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 /// The default [`Padding`] of a [`TextInput`].
@@ -84,24 +85,12 @@ pub const DEFAULT_PADDING: Padding = Padding::new(5.0);
 impl<'a, Message, Theme, Renderer> TextInput<'a, Message, Theme, Renderer>
 where
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// Creates a new [`TextInput`] with the given placeholder and
     /// its current value.
-    pub fn new(placeholder: &str, value: &str) -> Self
+    pub fn new(placeholder: &str, value: &str) -> Self {
-    where
-        Theme: DefaultStyle + 'a,
-    {
-        Self::with_style(placeholder, value, Theme::default_style)
-    }
-
-    /// Creates a new [`TextInput`] with the given placeholder,
-    /// its current value, and its style.
-    pub fn with_style(
-        placeholder: &str,
-        value: &str,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
-    ) -> Self {
         TextInput {
             id: None,
             placeholder: String::from(placeholder),
@@ -116,7 +105,7 @@ where
             on_paste: None,
             on_submit: None,
             icon: None,
-            style: Box::new(style),
+            class: Theme::default(),
         }
     }
 
@@ -203,11 +192,19 @@ where
     }
 
     /// Sets the style of the [`TextInput`].
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`TextInput`].
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 
@@ -345,15 +342,15 @@ where
             Status::Active
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
         renderer.fill_quad(
             renderer::Quad {
                 bounds,
-                border: appearance.border,
+                border: style.border,
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
         if self.icon.is_some() {
@@ -362,7 +359,7 @@ where
             renderer.fill_paragraph(
                 &state.icon,
                 icon_layout.bounds().center(),
-                appearance.icon,
+                style.icon,
                 *viewport,
             );
         }
@@ -401,7 +398,7 @@ where
                                 },
                                 ..renderer::Quad::default()
                             },
-                            appearance.value,
+                            style.value,
                         ))
                     } else {
                         None
@@ -440,7 +437,7 @@ where
                                 },
                                 ..renderer::Quad::default()
                             },
-                            appearance.selection,
+                            style.selection,
                         )),
                         if end == right {
                             right_offset
@@ -475,9 +472,9 @@ where
                 Point::new(text_bounds.x, text_bounds.center_y())
                     - Vector::new(offset, 0.0),
                 if text.is_empty() {
-                    appearance.placeholder
+                    style.placeholder
                 } else {
-                    appearance.value
+                    style.value
                 },
                 viewport,
             );
@@ -496,6 +493,7 @@ impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for TextInput<'a, Message, Theme, Renderer>
 where
     Message: Clone,
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn tag(&self) -> tree::Tag {
@@ -1058,8 +1056,8 @@ where
 impl<'a, Message, Theme, Renderer> From<TextInput<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
-    Message: 'a + Clone,
+    Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(
@@ -1400,7 +1398,7 @@ pub enum Status {
 
 /// The appearance of a text input.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The [`Background`] of the text input.
     pub background: Background,
     /// The [`Border`] of the text input.
@@ -1415,32 +1413,40 @@ pub struct Appearance {
     pub selection: Color,
 }
 
-/// The style of a [`TextInput`].
+/// The theme catalog of a [`TextInput`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`TextInput`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`TextInput`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`TextInput`].
-    fn default_style(&self, status: Status) -> Appearance {
+///
-        default(self, status)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`TextInput`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
-    let active = Appearance {
+    let active = Style {
         background: Background::Color(palette.background.base.color),
         border: Border {
             radius: 2.0.into(),
@@ -1455,21 +1461,21 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
 
     match status {
         Status::Active => active,
-        Status::Hovered => Appearance {
+        Status::Hovered => Style {
             border: Border {
                 color: palette.background.base.text,
                 ..active.border
             },
             ..active
         },
-        Status::Focused => Appearance {
+        Status::Focused => Style {
             border: Border {
                 color: palette.primary.strong.color,
                 ..active.border
             },
             ..active
         },
-        Status::Disabled => Appearance {
+        Status::Disabled => Style {
             background: Background::Color(palette.background.weak.color),
             value: active.placeholder,
             ..active

widget/src/themer.rs

@@ -155,9 +155,9 @@ where
         if let Some(background) = self.background {
             container::draw_background(
                 renderer,
-                &container::Appearance {
+                &container::Style {
                     background: Some(background(&theme)),
-                    ..container::Appearance::default()
+                    ..container::Style::default()
                 },
                 layout.bounds(),
             );

widget/src/toggler.rs

@@ -35,6 +35,7 @@ pub struct Toggler<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     is_toggled: bool,
@@ -48,11 +49,12 @@ pub struct Toggler<
     text_shaping: text::Shaping,
     spacing: f32,
     font: Option<Renderer::Font>,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Toggler<'a, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     /// The default size of a [`Toggler`].
@@ -72,7 +74,6 @@ where
         f: F,
     ) -> Self
     where
-        Theme: 'a + DefaultStyle,
         F: 'a + Fn(bool) -> Message,
     {
         Toggler {
@@ -87,7 +88,7 @@ where
             text_shaping: text::Shaping::Basic,
             spacing: Self::DEFAULT_SIZE / 2.0,
             font: None,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -145,11 +146,20 @@ where
     }
 
     /// Sets the style of the [`Toggler`].
-    pub fn style(
+    #[must_use]
-        mut self,
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
+    where
-    ) -> Self {
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
-        self.style = Box::new(style);
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Toggler`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -157,6 +167,7 @@ where
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Toggler<'a, Message, Theme, Renderer>
 where
+    Theme: Catalog,
     Renderer: text::Renderer,
 {
     fn tag(&self) -> tree::Tag {
@@ -284,7 +295,7 @@ where
                 style,
                 label_layout,
                 tree.state.downcast_ref(),
-                crate::text::Appearance::default(),
+                crate::text::Style::default(),
                 viewport,
             );
         }
@@ -302,7 +313,7 @@ where
             }
         };
 
-        let appearance = (self.style)(theme, status);
+        let style = theme.style(&self.class, status);
 
         let border_radius = bounds.height / BORDER_RADIUS_RATIO;
         let space = SPACE_RATIO * bounds.height;
@@ -319,12 +330,12 @@ where
                 bounds: toggler_background_bounds,
                 border: Border {
                     radius: border_radius.into(),
-                    width: appearance.background_border_width,
+                    width: style.background_border_width,
-                    color: appearance.background_border_color,
+                    color: style.background_border_color,
                 },
                 ..renderer::Quad::default()
             },
-            appearance.background,
+            style.background,
         );
 
         let toggler_foreground_bounds = Rectangle {
@@ -344,12 +355,12 @@ where
                 bounds: toggler_foreground_bounds,
                 border: Border {
                     radius: border_radius.into(),
-                    width: appearance.foreground_border_width,
+                    width: style.foreground_border_width,
-                    color: appearance.foreground_border_color,
+                    color: style.foreground_border_color,
                 },
                 ..renderer::Quad::default()
             },
-            appearance.foreground,
+            style.foreground,
         );
     }
 }
@@ -358,7 +369,7 @@ impl<'a, Message, Theme, Renderer> From<Toggler<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(
@@ -385,7 +396,7 @@ pub enum Status {
 
 /// The appearance of a toggler.
 #[derive(Debug, Clone, Copy)]
-pub struct Appearance {
+pub struct Style {
     /// The background [`Color`] of the toggler.
     pub background: Color,
     /// The width of the background border of the toggler.
@@ -400,29 +411,37 @@ pub struct Appearance {
     pub foreground_border_color: Color,
 }
 
-/// The style of a [`Toggler`].
+/// The theme catalog of a [`Toggler`].
-pub type Style<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Appearance + 'a>;
+pub trait Catalog: Sized {
+    /// The item class of the [`Catalog`].
+    type Class<'a>;
 
-/// The default style of a [`Toggler`].
+    /// The default class produced by the [`Catalog`].
-pub trait DefaultStyle {
+    fn default<'a>() -> Self::Class<'a>;
-    /// Returns the default style of a [`Toggler`].
+
-    fn default_style(&self, status: Status) -> Appearance;
+    /// The [`Style`] of a class with the given status.
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style;
 }
 
-impl DefaultStyle for Theme {
+/// A styling function for a [`Toggler`].
-    fn default_style(&self, status: Status) -> Appearance {
+///
-        default(self, status)
+/// This is just a boxed closure: `Fn(&Theme, Status) -> Style`.
+pub type StyleFn<'a, Theme> = Box<dyn Fn(&Theme, Status) -> Style + 'a>;
+
+impl Catalog for Theme {
+    type Class<'a> = StyleFn<'a, Self>;
+
+    fn default<'a>() -> Self::Class<'a> {
+        Box::new(default)
     }
-}
 
-impl DefaultStyle for Appearance {
+    fn style(&self, class: &Self::Class<'_>, status: Status) -> Style {
-    fn default_style(&self, _status: Status) -> Appearance {
+        class(self, status)
-        *self
     }
 }
 
 /// The default style of a [`Toggler`].
-pub fn default(theme: &Theme, status: Status) -> Appearance {
+pub fn default(theme: &Theme, status: Status) -> Style {
     let palette = theme.extended_palette();
 
     let background = match status {
@@ -455,7 +474,7 @@ pub fn default(theme: &Theme, status: Status) -> Appearance {
         }
     };
 
-    Appearance {
+    Style {
         background,
         foreground,
         foreground_border_width: 0.0,

widget/src/tooltip.rs

@@ -20,6 +20,7 @@ pub struct Tooltip<
     Theme = crate::Theme,
     Renderer = crate::Renderer,
 > where
+    Theme: container::Catalog,
     Renderer: text::Renderer,
 {
     content: Element<'a, Message, Theme, Renderer>,
@@ -28,11 +29,12 @@ pub struct Tooltip<
     gap: f32,
     padding: f32,
     snap_within_viewport: bool,
-    style: container::Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, Message, Theme, Renderer> Tooltip<'a, Message, Theme, Renderer>
 where
+    Theme: container::Catalog,
     Renderer: text::Renderer,
 {
     /// The default padding of a [`Tooltip`] drawn by this renderer.
@@ -45,10 +47,7 @@ where
         content: impl Into<Element<'a, Message, Theme, Renderer>>,
         tooltip: impl Into<Element<'a, Message, Theme, Renderer>>,
         position: Position,
-    ) -> Self
+    ) -> Self {
-    where
-        Theme: container::DefaultStyle + 'a,
-    {
         Tooltip {
             content: content.into(),
             tooltip: tooltip.into(),
@@ -56,7 +55,7 @@ where
             gap: 0.0,
             padding: Self::DEFAULT_PADDING,
             snap_within_viewport: true,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -79,11 +78,23 @@ where
     }
 
     /// Sets the style of the [`Tooltip`].
+    #[must_use]
     pub fn style(
         mut self,
-        style: impl Fn(&Theme, container::Status) -> container::Appearance + 'a,
+        style: impl Fn(&Theme) -> container::Style + 'a,
-    ) -> Self {
+    ) -> Self
-        self.style = Box::new(style);
+    where
+        Theme::Class<'a>: From<container::StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as container::StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`Tooltip`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
         self
     }
 }
@@ -91,6 +102,7 @@ where
 impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
     for Tooltip<'a, Message, Theme, Renderer>
 where
+    Theme: container::Catalog,
     Renderer: text::Renderer,
 {
     fn children(&self) -> Vec<widget::Tree> {
@@ -239,7 +251,7 @@ where
                 positioning: self.position,
                 gap: self.gap,
                 padding: self.padding,
-                style: &self.style,
+                class: &self.class,
             })))
         } else {
             None
@@ -262,7 +274,7 @@ impl<'a, Message, Theme, Renderer> From<Tooltip<'a, Message, Theme, Renderer>>
     for Element<'a, Message, Theme, Renderer>
 where
     Message: 'a,
-    Theme: 'a,
+    Theme: container::Catalog + 'a,
     Renderer: text::Renderer + 'a,
 {
     fn from(
@@ -299,6 +311,7 @@ enum State {
 
 struct Overlay<'a, 'b, Message, Theme, Renderer>
 where
+    Theme: container::Catalog,
     Renderer: text::Renderer,
 {
     position: Point,
@@ -310,14 +323,14 @@ where
     positioning: Position,
     gap: f32,
     padding: f32,
-    style:
+    class: &'b Theme::Class<'a>,
-        &'b (dyn Fn(&Theme, container::Status) -> container::Appearance + 'a),
 }
 
 impl<'a, 'b, Message, Theme, Renderer>
     overlay::Overlay<Message, Theme, Renderer>
     for Overlay<'a, 'b, Message, Theme, Renderer>
 where
+    Theme: container::Catalog,
     Renderer: text::Renderer,
 {
     fn layout(&mut self, renderer: &Renderer, bounds: Size) -> layout::Node {
@@ -426,7 +439,7 @@ where
         layout: Layout<'_>,
         cursor_position: mouse::Cursor,
     ) {
-        let style = (self.style)(theme, container::Status::Idle);
+        let style = theme.style(self.class);
 
         container::draw_background(renderer, &style, layout.bounds());
 

widget/src/vertical_slider.rs

@@ -2,10 +2,9 @@
 use std::ops::RangeInclusive;
 
 pub use crate::slider::{
-    default, Appearance, DefaultStyle, Handle, HandleShape, Status, Style,
+    default, Catalog, Handle, HandleShape, Status, Style, StyleFn,
 };
 
-use crate::core;
 use crate::core::event::{self, Event};
 use crate::core::keyboard;
 use crate::core::keyboard::key::{self, Key};
@@ -15,8 +14,8 @@ use crate::core::renderer;
 use crate::core::touch;
 use crate::core::widget::tree::{self, Tree};
 use crate::core::{
-    Border, Clipboard, Element, Length, Pixels, Point, Rectangle, Shell, Size,
+    self, Border, Clipboard, Element, Length, Pixels, Point, Rectangle, Shell,
-    Widget,
+    Size, Widget,
 };
 
 /// An vertical bar and a handle that selects a single value from a range of
@@ -41,7 +40,10 @@ use crate::core::{
 /// VerticalSlider::new(0.0..=100.0, value, Message::SliderChanged);
 /// ```
 #[allow(missing_debug_implementations)]
-pub struct VerticalSlider<'a, T, Message, Theme = crate::Theme> {
+pub struct VerticalSlider<'a, T, Message, Theme = crate::Theme>
+where
+    Theme: Catalog,
+{
     range: RangeInclusive<T>,
     step: T,
     shift_step: Option<T>,
@@ -51,13 +53,14 @@ pub struct VerticalSlider<'a, T, Message, Theme = crate::Theme> {
     on_release: Option<Message>,
     width: f32,
     height: Length,
-    style: Style<'a, Theme>,
+    class: Theme::Class<'a>,
 }
 
 impl<'a, T, Message, Theme> VerticalSlider<'a, T, Message, Theme>
 where
     T: Copy + From<u8> + std::cmp::PartialOrd,
     Message: Clone,
+    Theme: Catalog,
 {
     /// The default width of a [`VerticalSlider`].
     pub const DEFAULT_WIDTH: f32 = 16.0;
@@ -72,7 +75,6 @@ where
     ///   `Message`.
     pub fn new<F>(range: RangeInclusive<T>, value: T, on_change: F) -> Self
     where
-        Theme: DefaultStyle + 'a,
         F: 'a + Fn(T) -> Message,
     {
         let value = if value >= *range.start() {
@@ -97,7 +99,7 @@ where
             on_release: None,
             width: Self::DEFAULT_WIDTH,
             height: Length::Fill,
-            style: Box::new(Theme::default_style),
+            class: Theme::default(),
         }
     }
 
@@ -132,15 +134,6 @@ where
         self
     }
 
-    /// Sets the style of the [`VerticalSlider`].
-    pub fn style(
-        mut self,
-        style: impl Fn(&Theme, Status) -> Appearance + 'a,
-    ) -> Self {
-        self.style = Box::new(style);
-        self
-    }
-
     /// Sets the step size of the [`VerticalSlider`].
     pub fn step(mut self, step: T) -> Self {
         self.step = step;
@@ -154,6 +147,24 @@ where
         self.shift_step = Some(shift_step.into());
         self
     }
+
+    /// Sets the style of the [`VerticalSlider`].
+    #[must_use]
+    pub fn style(mut self, style: impl Fn(&Theme, Status) -> Style + 'a) -> Self
+    where
+        Theme::Class<'a>: From<StyleFn<'a, Theme>>,
+    {
+        self.class = (Box::new(style) as StyleFn<'a, Theme>).into();
+        self
+    }
+
+    /// Sets the style class of the [`VerticalSlider`].
+    #[cfg(feature = "advanced")]
+    #[must_use]
+    pub fn class(mut self, class: impl Into<Theme::Class<'a>>) -> Self {
+        self.class = class.into();
+        self
+    }
 }
 
 impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
@@ -161,6 +172,7 @@ impl<'a, T, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
 where
     T: Copy + Into<f64> + num_traits::FromPrimitive,
     Message: Clone,
+    Theme: Catalog,
     Renderer: core::Renderer,
 {
     fn tag(&self) -> tree::Tag {
@@ -354,8 +366,8 @@ where
         let bounds = layout.bounds();
         let is_mouse_over = cursor.is_over(bounds);
 
-        let style = (self.style)(
+        let style = theme.style(
-            theme,
+            &self.class,
             if state.is_dragging {
                 Status::Dragged
             } else if is_mouse_over {
@@ -467,7 +479,7 @@ impl<'a, T, Message, Theme, Renderer>
 where
     T: Copy + Into<f64> + num_traits::FromPrimitive + 'a,
     Message: Clone + 'a,
-    Theme: 'a,
+    Theme: Catalog + 'a,
     Renderer: core::Renderer + 'a,
 {
     fn from(