Draft first-class Theme support

RFC: https://github.com/iced-rs/rfcs/pull/6

style/src/button.rs

@@ -27,10 +27,12 @@ impl std::default::Default for Style {
 
 /// A set of rules that dictate the style of a button.
 pub trait StyleSheet {
-    fn active(&self) -> Style;
+    type Variant;
 
-    fn hovered(&self) -> Style {
-        let active = self.active();
+    fn active(&self, variant: Self::Variant) -> Style;
+
+    fn hovered(&self, variant: Self::Variant) -> Style {
+        let active = self.active(variant);
 
         Style {
             shadow_offset: active.shadow_offset + Vector::new(0.0, 1.0),
@@ -38,15 +40,15 @@ pub trait StyleSheet {
         }
     }
 
-    fn pressed(&self) -> Style {
+    fn pressed(&self, variant: Self::Variant) -> Style {
         Style {
             shadow_offset: Vector::default(),
-            ..self.active()
+            ..self.active(variant)
         }
     }
 
-    fn disabled(&self) -> Style {
-        let active = self.active();
+    fn disabled(&self, variant: Self::Variant) -> Style {
+        let active = self.active(variant);
 
         Style {
             shadow_offset: Vector::default(),
@@ -64,33 +66,3 @@ pub trait StyleSheet {
         }
     }
 }
-
-struct Default;
-
-impl StyleSheet for Default {
-    fn active(&self) -> Style {
-        Style {
-            shadow_offset: Vector::new(0.0, 0.0),
-            background: Some(Background::Color([0.87, 0.87, 0.87].into())),
-            border_radius: 2.0,
-            border_width: 1.0,
-            border_color: [0.7, 0.7, 0.7].into(),
-            text_color: Color::BLACK,
-        }
-    }
-}
-
-impl<'a> std::default::Default for Box<dyn StyleSheet + 'a> {
-    fn default() -> Self {
-        Box::new(Default)
-    }
-}
-
-impl<'a, T> From<T> for Box<dyn StyleSheet + 'a>
-where
-    T: StyleSheet + 'a,
-{
-    fn from(style_sheet: T) -> Self {
-        Box::new(style_sheet)
-    }
-}

style/src/lib.rs

@@ -21,4 +21,7 @@ pub mod rule;
 pub mod scrollable;
 pub mod slider;
 pub mod text_input;
+pub mod theme;
 pub mod toggler;
+
+pub use theme::Theme;

style/src/theme.rs

@@ -0,0 +1,45 @@
+use crate::button;
+
+use iced_core::{Color, Vector};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Theme {
+    Light,
+    Dark,
+}
+
+impl Default for Theme {
+    fn default() -> Self {
+        Self::Light
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Button {
+    Primary,
+    Secondary,
+    Positive,
+    Destructive,
+    Text,
+}
+
+impl Default for Button {
+    fn default() -> Self {
+        Self::Primary
+    }
+}
+
+impl button::StyleSheet for Theme {
+    type Variant = Button;
+
+    fn active(&self, _variant: Self::Variant) -> button::Style {
+        button::Style {
+            shadow_offset: Vector::default(),
+            background: None,
+            border_radius: 0.0,
+            border_width: 0.0,
+            border_color: Color::TRANSPARENT,
+            text_color: Color::BLACK,
+        }
+    }
+}