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core/src/widget/button.rs

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+//! Allow your users to perform actions by pressing a button.
+//!
+//! A [`Button`] has some local [`State`] and a [`Class`].
+//!
+//! [`Button`]: struct.Button.html
+//! [`State`]: struct.State.html
+//! [`Class`]: enum.Class.html
+
+use crate::input::{mouse, ButtonState};
+use crate::{
+    Align, Element, Event, Hasher, Layout, MouseCursor, Node, Point, Rectangle,
+    Style, Widget,
+};
+
+use std::hash::Hash;
+
+/// A generic widget that produces a message when clicked.
+///
+/// It implements [`Widget`] when the associated `Renderer` implements the
+/// [`button::Renderer`] trait.
+///
+/// [`Widget`]: ../trait.Widget.html
+/// [`button::Renderer`]: trait.Renderer.html
+///
+/// # Example
+///
+/// ```
+/// use iced::{button, Button};
+///
+/// pub enum Message {
+///     ButtonClicked,
+/// }
+///
+/// let state = &mut button::State::new();
+///
+/// Button::new(state, "Click me!")
+///     .on_press(Message::ButtonClicked);
+/// ```
+///
+/// ![Button drawn by Coffee's renderer](https://github.com/hecrj/coffee/blob/bda9818f823dfcb8a7ad0ff4940b4d4b387b5208/images/ui/button.png?raw=true)
+pub struct Button<'a, Message> {
+    state: &'a mut State,
+    label: String,
+    class: Class,
+    on_press: Option<Message>,
+    style: Style,
+}
+
+impl<'a, Message> std::fmt::Debug for Button<'a, Message>
+where
+    Message: std::fmt::Debug,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Button")
+            .field("state", &self.state)
+            .field("label", &self.label)
+            .field("class", &self.class)
+            .field("on_press", &self.on_press)
+            .field("style", &self.style)
+            .finish()
+    }
+}
+
+impl<'a, Message> Button<'a, Message> {
+    /// Creates a new [`Button`] with some local [`State`] and the given label.
+    ///
+    /// The default [`Class`] of a new [`Button`] is [`Class::Primary`].
+    ///
+    /// [`Button`]: struct.Button.html
+    /// [`State`]: struct.State.html
+    /// [`Class`]: enum.Class.html
+    /// [`Class::Primary`]: enum.Class.html#variant.Primary
+    pub fn new(state: &'a mut State, label: &str) -> Self {
+        Button {
+            state,
+            label: String::from(label),
+            class: Class::Primary,
+            on_press: None,
+            style: Style::default().min_width(100),
+        }
+    }
+
+    /// Sets the width of the [`Button`] in pixels.
+    ///
+    /// [`Button`]: struct.Button.html
+    pub fn width(mut self, width: u16) -> Self {
+        self.style = self.style.width(width);
+        self
+    }
+
+    /// Makes the [`Button`] fill the horizontal space of its container.
+    ///
+    /// [`Button`]: struct.Button.html
+    pub fn fill_width(mut self) -> Self {
+        self.style = self.style.fill_width();
+        self
+    }
+
+    /// Sets the alignment of the [`Button`] itself.
+    ///
+    /// This is useful if you want to override the default alignment given by
+    /// the parent container.
+    ///
+    /// [`Button`]: struct.Button.html
+    pub fn align_self(mut self, align: Align) -> Self {
+        self.style = self.style.align_self(align);
+        self
+    }
+
+    /// Sets the [`Class`] of the [`Button`].
+    ///
+    ///
+    /// [`Button`]: struct.Button.html
+    /// [`Class`]: enum.Class.html
+    pub fn class(mut self, class: Class) -> Self {
+        self.class = class;
+        self
+    }
+
+    /// Sets the message that will be produced when the [`Button`] is pressed.
+    ///
+    /// [`Button`]: struct.Button.html
+    pub fn on_press(mut self, msg: Message) -> Self {
+        self.on_press = Some(msg);
+        self
+    }
+}
+
+impl<'a, Message, Renderer> Widget<Message, Renderer> for Button<'a, Message>
+where
+    Renderer: self::Renderer,
+    Message: Copy + std::fmt::Debug,
+{
+    fn node(&self, _renderer: &Renderer) -> Node {
+        Node::new(self.style.height(50))
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+    ) {
+        match event {
+            Event::Mouse(mouse::Event::Input {
+                button: mouse::Button::Left,
+                state,
+            }) => {
+                if let Some(on_press) = self.on_press {
+                    let bounds = layout.bounds();
+
+                    match state {
+                        ButtonState::Pressed => {
+                            self.state.is_pressed =
+                                bounds.contains(cursor_position);
+                        }
+                        ButtonState::Released => {
+                            let is_clicked = self.state.is_pressed
+                                && bounds.contains(cursor_position);
+
+                            self.state.is_pressed = false;
+
+                            if is_clicked {
+                                messages.push(on_press);
+                            }
+                        }
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> MouseCursor {
+        renderer.draw(
+            cursor_position,
+            layout.bounds(),
+            self.state,
+            &self.label,
+            self.class,
+        )
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        self.style.hash(state);
+    }
+}
+
+/// The local state of a [`Button`].
+///
+/// [`Button`]: struct.Button.html
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct State {
+    is_pressed: bool,
+}
+
+impl State {
+    /// Creates a new [`State`].
+    ///
+    /// [`State`]: struct.State.html
+    pub fn new() -> State {
+        State::default()
+    }
+
+    /// Returns whether the associated [`Button`] is currently being pressed or
+    /// not.
+    ///
+    /// [`Button`]: struct.Button.html
+    pub fn is_pressed(&self) -> bool {
+        self.is_pressed
+    }
+}
+
+/// The type of a [`Button`].
+///
+/// ![Different buttons drawn by the built-in renderer in Coffee](https://github.com/hecrj/coffee/blob/bda9818f823dfcb8a7ad0ff4940b4d4b387b5208/images/ui/button_classes.png?raw=true)
+///
+/// [`Button`]: struct.Button.html
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Class {
+    /// The [`Button`] performs the main action.
+    ///
+    /// [`Button`]: struct.Button.html
+    Primary,
+
+    /// The [`Button`] performs an alternative action.
+    ///
+    /// [`Button`]: struct.Button.html
+    Secondary,
+
+    /// The [`Button`] performs a productive action.
+    ///
+    /// [`Button`]: struct.Button.html
+    Positive,
+}
+
+/// The renderer of a [`Button`].
+///
+/// Your [renderer] will need to implement this trait before being
+/// able to use a [`Button`] in your user interface.
+///
+/// [`Button`]: struct.Button.html
+/// [renderer]: ../../renderer/index.html
+pub trait Renderer {
+    /// Draws a [`Button`].
+    ///
+    /// It receives:
+    ///   * the current cursor position
+    ///   * the bounds of the [`Button`]
+    ///   * the local state of the [`Button`]
+    ///   * the label of the [`Button`]
+    ///   * the [`Class`] of the [`Button`]
+    ///
+    /// [`Button`]: struct.Button.html
+    /// [`State`]: struct.State.html
+    /// [`Class`]: enum.Class.html
+    fn draw(
+        &mut self,
+        cursor_position: Point,
+        bounds: Rectangle,
+        state: &State,
+        label: &str,
+        class: Class,
+    ) -> MouseCursor;
+}
+
+impl<'a, Message, Renderer> From<Button<'a, Message>>
+    for Element<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
+    Message: 'static + Copy + std::fmt::Debug,
+{
+    fn from(button: Button<'a, Message>) -> Element<'a, Message, Renderer> {
+        Element::new(button)
+    }
+}