Create `iced_widget` subcrate and re-organize the whole codebase

1 files changed, 145 insertions, 0 deletions

diff --git a/core/src/widget.rs b/core/src/widget.rs
new file mode 100644
index 00000000..70e2c2d9
--- /dev/null
+++ b/core/src/widget.rs
@@ -0,0 +1,145 @@
+//! Create custom widgets and operate on them.
+pub mod operation;
+pub mod text;
+pub mod tree;
+
+mod id;
+
+pub use id::Id;
+pub use operation::Operation;
+pub use text::Text;
+pub use tree::Tree;
+
+use crate::event::{self, Event};
+use crate::layout::{self, Layout};
+use crate::mouse;
+use crate::overlay;
+use crate::renderer;
+use crate::{Clipboard, Length, Point, Rectangle, Shell};
+
+/// A component that displays information and allows interaction.
+///
+/// If you want to build your own widgets, you will need to implement this
+/// trait.
+///
+/// # Examples
+/// The repository has some [examples] showcasing how to implement a custom
+/// widget:
+///
+/// - [`bezier_tool`], a Paint-like tool for drawing Bézier curves using
+/// [`lyon`].
+/// - [`custom_widget`], a demonstration of how to build a custom widget that
+/// draws a circle.
+/// - [`geometry`], a custom widget showcasing how to draw geometry with the
+/// `Mesh2D` primitive in [`iced_wgpu`].
+///
+/// [examples]: https://github.com/iced-rs/iced/tree/0.8/examples
+/// [`bezier_tool`]: https://github.com/iced-rs/iced/tree/0.8/examples/bezier_tool
+/// [`custom_widget`]: https://github.com/iced-rs/iced/tree/0.8/examples/custom_widget
+/// [`geometry`]: https://github.com/iced-rs/iced/tree/0.8/examples/geometry
+/// [`lyon`]: https://github.com/nical/lyon
+/// [`iced_wgpu`]: https://github.com/iced-rs/iced/tree/0.8/wgpu
+pub trait Widget<Message, Renderer>
+where
+    Renderer: crate::Renderer,
+{
+    /// Returns the width of the [`Widget`].
+    fn width(&self) -> Length;
+
+    /// Returns the height of the [`Widget`].
+    fn height(&self) -> Length;
+
+    /// Returns the [`layout::Node`] of the [`Widget`].
+    ///
+    /// This [`layout::Node`] is used by the runtime to compute the [`Layout`] of the
+    /// user interface.
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node;
+
+    /// Draws the [`Widget`] using the associated `Renderer`.
+    fn draw(
+        &self,
+        state: &Tree,
+        renderer: &mut Renderer,
+        theme: &Renderer::Theme,
+        style: &renderer::Style,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        viewport: &Rectangle,
+    );
+
+    /// Returns the [`Tag`] of the [`Widget`].
+    ///
+    /// [`Tag`]: tree::Tag
+    fn tag(&self) -> tree::Tag {
+        tree::Tag::stateless()
+    }
+
+    /// Returns the [`State`] of the [`Widget`].
+    ///
+    /// [`State`]: tree::State
+    fn state(&self) -> tree::State {
+        tree::State::None
+    }
+
+    /// Returns the state [`Tree`] of the children of the [`Widget`].
+    fn children(&self) -> Vec<Tree> {
+        Vec::new()
+    }
+
+    /// Reconciliates the [`Widget`] with the provided [`Tree`].
+    fn diff(&self, _tree: &mut Tree) {}
+
+    /// Applies an [`Operation`] to the [`Widget`].
+    fn operate(
+        &self,
+        _state: &mut Tree,
+        _layout: Layout<'_>,
+        _renderer: &Renderer,
+        _operation: &mut dyn Operation<Message>,
+    ) {
+    }
+
+    /// Processes a runtime [`Event`].
+    ///
+    /// By default, it does nothing.
+    fn on_event(
+        &mut self,
+        _state: &mut Tree,
+        _event: Event,
+        _layout: Layout<'_>,
+        _cursor_position: Point,
+        _renderer: &Renderer,
+        _clipboard: &mut dyn Clipboard,
+        _shell: &mut Shell<'_, Message>,
+    ) -> event::Status {
+        event::Status::Ignored
+    }
+
+    /// Returns the current [`mouse::Interaction`] of the [`Widget`].
+    ///
+    /// By default, it returns [`mouse::Interaction::Idle`].
+    fn mouse_interaction(
+        &self,
+        _state: &Tree,
+        _layout: Layout<'_>,
+        _cursor_position: Point,
+        _viewport: &Rectangle,
+        _renderer: &Renderer,
+    ) -> mouse::Interaction {
+        mouse::Interaction::Idle
+    }
+
+    /// Returns the overlay of the [`Widget`], if there is any.
+    fn overlay<'a>(
+        &'a mut self,
+        _state: &'a mut Tree,
+        _layout: Layout<'_>,
+        _renderer: &Renderer,
+    ) -> Option<overlay::Element<'a, Message, Renderer>> {
+        None
+    }
+}