Decouple iced from coffee

src/widget.rs

@@ -0,0 +1,103 @@
+//! Use the built-in widgets in your user interface.
+//!
+//! # Customization
+//! Every drawable widget has its own module with a `Renderer` trait that must
+//! be implemented by a custom renderer before being able to use the
+//! widget.
+//!
+//! The built-in [`Renderer`] supports all the widgets in this module!
+//!
+//! [`ui` module]: ../index.html
+//! [`Row`]: struct.Row.html
+//! [`Column`]: struct.Column.html
+//! [`Renderer`]: ../struct.Renderer.html
+mod column;
+mod row;
+
+pub mod button;
+pub mod checkbox;
+pub mod radio;
+pub mod slider;
+pub mod text;
+
+pub use button::Button;
+pub use checkbox::Checkbox;
+pub use column::Column;
+pub use radio::Radio;
+pub use row::Row;
+pub use slider::Slider;
+pub use text::Text;
+
+use crate::{Event, Hasher, Layout, MouseCursor, Node, Point};
+
+/// A component that displays information or allows interaction.
+///
+/// If you want to build a custom widget, you will need to implement this trait.
+/// Additionally, remember to also provide [`Into<Element>`] so your users can
+/// easily turn your [`Widget`] into a generic [`Element`]
+///
+/// [`Into<Element>`]: struct.Element.html
+/// [`Widget`]: trait.Widget.html
+/// [`Element`]: struct.Element.html
+pub trait Widget<Message, Renderer>: std::fmt::Debug {
+    /// Returns the [`Node`] of the [`Widget`].
+    ///
+    /// This [`Node`] is used by the runtime to compute the [`Layout`] of the
+    /// user interface.
+    ///
+    /// [`Node`]: struct.Node.html
+    /// [`Widget`]: trait.Widget.html
+    /// [`Layout`]: struct.Layout.html
+    fn node(&self, renderer: &Renderer) -> Node;
+
+    /// Draws the [`Widget`] using the associated `Renderer`.
+    ///
+    /// It must return the [`MouseCursor`] state for the [`Widget`].
+    ///
+    /// [`Widget`]: trait.Widget.html
+    /// [`MouseCursor`]: enum.MouseCursor.html
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> MouseCursor;
+
+    /// Computes the _layout_ hash of the [`Widget`].
+    ///
+    /// The produced hash is used by the runtime to decide if the [`Layout`]
+    /// needs to be recomputed between frames. Therefore, to ensure maximum
+    /// efficiency, the hash should only be affected by the properties of the
+    /// [`Widget`] that can affect layouting.
+    ///
+    /// For example, the [`Text`] widget does not hash its color property, as
+    /// its value cannot affect the overall [`Layout`] of the user interface.
+    ///
+    /// [`Widget`]: trait.Widget.html
+    /// [`Layout`]: struct.Layout.html
+    /// [`Text`]: ../widget/text/struct.Text.html
+    fn hash(&self, state: &mut Hasher);
+
+    /// Processes a runtime [`Event`].
+    ///
+    /// It receives:
+    ///   * an [`Event`] describing user interaction
+    ///   * the computed [`Layout`] of the [`Widget`]
+    ///   * the current cursor position
+    ///   * a mutable `Message` vector, allowing the [`Widget`] to produce
+    ///   new messages based on user interaction.
+    ///
+    /// By default, it does nothing.
+    ///
+    /// [`Event`]: enum.Event.html
+    /// [`Widget`]: trait.Widget.html
+    /// [`Layout`]: struct.Layout.html
+    fn on_event(
+        &mut self,
+        _event: Event,
+        _layout: Layout<'_>,
+        _cursor_position: Point,
+        _messages: &mut Vec<Message>,
+    ) {
+    }
+}