Implement `Slider` in `iced_pure`

2 files changed, 270 insertions, 2 deletions

diff --git a/pure/src/widget.rs b/pure/src/widget.rs
index 93298c61..009741a8 100644
--- a/pure/src/widget.rs
+++ b/pure/src/widget.rs
@@ -7,6 +7,7 @@ mod container;
 mod element;
 mod row;
 mod scrollable;
+mod slider;
 mod text;
 mod text_input;
 mod tree;
@@ -19,6 +20,7 @@ pub use element::Element;
 pub use image::Image;
 pub use row::Row;
 pub use scrollable::Scrollable;
+pub use slider::Slider;
 pub use text::Text;
 pub use text_input::TextInput;
 pub use tree::Tree;
@@ -36,8 +38,6 @@ pub trait Widget<Message, Renderer> {
 
     fn state(&self) -> Box<dyn Any>;
 
-    fn diff(&self, tree: &mut Tree);
-
     fn children_state(&self) -> Vec<Tree>;
 
     fn width(&self) -> Length;
@@ -62,6 +62,8 @@ pub trait Widget<Message, Renderer> {
         viewport: &Rectangle,
     );
 
+    fn diff(&self, _tree: &mut Tree) {}
+
     fn mouse_interaction(
         &self,
         _state: &Tree,
@@ -149,6 +151,19 @@ where
     TextInput::new(placeholder, value, on_change)
 }
 
+pub fn slider<'a, Message, Renderer, T>(
+    range: std::ops::RangeInclusive<T>,
+    value: T,
+    on_change: impl Fn(T) -> Message + 'a,
+) -> Slider<'a, T, Message>
+where
+    Message: Clone,
+    Renderer: iced_native::Renderer,
+    T: Copy + From<u8> + std::cmp::PartialOrd,
+{
+    Slider::new(range, value, on_change)
+}
+
 pub fn image<Handle>(handle: Handle) -> Image<Handle> {
     Image::new(handle)
 }
diff --git a/pure/src/widget/slider.rs b/pure/src/widget/slider.rs
new file mode 100644
index 00000000..f659c2ed
--- /dev/null
+++ b/pure/src/widget/slider.rs
@@ -0,0 +1,253 @@
+//! Display an interactive selector of a single value from a range of values.
+//!
+//! A [`Slider`] has some local [`State`].
+use crate::{Element, Tree, Widget};
+
+use iced_native::event::{self, Event};
+use iced_native::layout;
+use iced_native::mouse;
+use iced_native::renderer;
+use iced_native::widget::slider;
+use iced_native::{
+    Clipboard, Hasher, Layout, Length, Point, Rectangle, Shell, Size,
+};
+
+use std::any::{self, Any};
+use std::ops::RangeInclusive;
+
+pub use iced_style::slider::{Handle, HandleShape, Style, StyleSheet};
+
+/// An horizontal bar and a handle that selects a single value from a range of
+/// values.
+///
+/// A [`Slider`] will try to fill the horizontal space of its container.
+///
+/// The [`Slider`] range of numeric values is generic and its step size defaults
+/// to 1 unit.
+///
+/// # Example
+/// ```
+/// # use iced_native::widget::slider::{self, Slider};
+/// #
+/// #[derive(Clone)]
+/// pub enum Message {
+///     SliderChanged(f32),
+/// }
+///
+/// let state = &mut slider::State::new();
+/// let value = 50.0;
+///
+/// Slider::new(state, 0.0..=100.0, value, Message::SliderChanged);
+/// ```
+///
+/// ![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> {
+    range: RangeInclusive<T>,
+    step: T,
+    value: T,
+    on_change: Box<dyn Fn(T) -> Message + 'a>,
+    on_release: Option<Message>,
+    width: Length,
+    height: u16,
+    style_sheet: Box<dyn StyleSheet + 'a>,
+}
+
+impl<'a, T, Message> Slider<'a, T, Message>
+where
+    T: Copy + From<u8> + std::cmp::PartialOrd,
+    Message: Clone,
+{
+    /// The default height of a [`Slider`].
+    pub const DEFAULT_HEIGHT: u16 = 22;
+
+    /// Creates a new [`Slider`].
+    ///
+    /// It expects:
+    ///   * an inclusive range of possible values
+    ///   * the current value of the [`Slider`]
+    ///   * a function that will be called when the [`Slider`] is dragged.
+    ///   It receives the new value of the [`Slider`] and must produce a
+    ///   `Message`.
+    pub fn new<F>(range: RangeInclusive<T>, value: T, on_change: F) -> Self
+    where
+        F: 'a + Fn(T) -> Message,
+    {
+        let value = if value >= *range.start() {
+            value
+        } else {
+            *range.start()
+        };
+
+        let value = if value <= *range.end() {
+            value
+        } else {
+            *range.end()
+        };
+
+        Slider {
+            value,
+            range,
+            step: T::from(1),
+            on_change: Box::new(on_change),
+            on_release: None,
+            width: Length::Fill,
+            height: Self::DEFAULT_HEIGHT,
+            style_sheet: Default::default(),
+        }
+    }
+
+    /// Sets the release message of the [`Slider`].
+    /// This is called when the mouse is released from the slider.
+    ///
+    /// Typically, the user's interaction with the slider is finished when this message is produced.
+    /// This is useful if you need to spawn a long-running task from the slider's result, where
+    /// the default on_change message could create too many events.
+    pub fn on_release(mut self, on_release: Message) -> Self {
+        self.on_release = Some(on_release);
+        self
+    }
+
+    /// Sets the width of the [`Slider`].
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Slider`].
+    pub fn height(mut self, height: u16) -> Self {
+        self.height = height;
+        self
+    }
+
+    /// Sets the style of the [`Slider`].
+    pub fn style(
+        mut self,
+        style_sheet: impl Into<Box<dyn StyleSheet + 'a>>,
+    ) -> Self {
+        self.style_sheet = style_sheet.into();
+        self
+    }
+
+    /// Sets the step size of the [`Slider`].
+    pub fn step(mut self, step: T) -> Self {
+        self.step = step;
+        self
+    }
+}
+
+impl<'a, T, Message, Renderer> Widget<Message, Renderer>
+    for Slider<'a, T, Message>
+where
+    T: Copy + Into<f64> + num_traits::FromPrimitive,
+    Message: Clone,
+    Renderer: iced_native::Renderer,
+{
+    fn tag(&self) -> any::TypeId {
+        any::TypeId::of::<slider::State>()
+    }
+
+    fn state(&self) -> Box<dyn Any> {
+        Box::new(slider::State::new())
+    }
+
+    fn children_state(&self) -> Vec<Tree> {
+        Vec::new()
+    }
+
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn height(&self) -> Length {
+        Length::Shrink
+    }
+
+    fn layout(
+        &self,
+        _renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits =
+            limits.width(self.width).height(Length::Units(self.height));
+
+        let size = limits.resolve(Size::ZERO);
+
+        layout::Node::new(size)
+    }
+
+    fn on_event(
+        &mut self,
+        tree: &mut Tree,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        _renderer: &Renderer,
+        _clipboard: &mut dyn Clipboard,
+        shell: &mut Shell<'_, Message>,
+    ) -> event::Status {
+        slider::update(
+            event,
+            layout,
+            cursor_position,
+            shell,
+            tree.state.downcast_mut::<slider::State>(),
+            &mut self.value,
+            &self.range,
+            self.step,
+            self.on_change.as_ref(),
+            &self.on_release,
+        )
+    }
+
+    fn draw(
+        &self,
+        tree: &Tree,
+        renderer: &mut Renderer,
+        _style: &renderer::Style,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        _viewport: &Rectangle,
+    ) {
+        slider::draw(
+            renderer,
+            layout,
+            cursor_position,
+            tree.state.downcast_ref::<slider::State>(),
+            self.value,
+            &self.range,
+            self.style_sheet.as_ref(),
+        )
+    }
+
+    fn mouse_interaction(
+        &self,
+        tree: &Tree,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        _viewport: &Rectangle,
+        _renderer: &Renderer,
+    ) -> mouse::Interaction {
+        slider::mouse_interaction(
+            layout,
+            cursor_position,
+            tree.state.downcast_ref::<slider::State>(),
+        )
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        slider::hash_layout(state, self.width)
+    }
+}
+
+impl<'a, T, Message, Renderer> From<Slider<'a, T, Message>>
+    for Element<'a, Message, Renderer>
+where
+    T: 'a + Copy + Into<f64> + num_traits::FromPrimitive,
+    Message: 'a + Clone,
+    Renderer: 'a + iced_native::Renderer,
+{
+    fn from(slider: Slider<'a, T, Message>) -> Element<'a, Message, Renderer> {
+        Element::new(slider)
+    }
+}