Provide Renderer to Widget::on_event

This allows us to implement configurable event processing that adapts to
different rendering strategies.

native/src/element.rs

@@ -299,6 +299,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<B>,
+        renderer: &Renderer,
     ) {
         let mut original_messages = Vec::new();
 
@@ -307,6 +308,7 @@ where
             layout,
             cursor_position,
             &mut original_messages,
+            renderer,
         );
 
         original_messages
@@ -369,10 +371,15 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        renderer: &Renderer,
     ) {
-        self.element
-            .widget
-            .on_event(event, layout, cursor_position, messages)
+        self.element.widget.on_event(
+            event,
+            layout,
+            cursor_position,
+            messages,
+            renderer,
+        )
     }
 
     fn draw(

native/src/user_interface.rs

@@ -186,7 +186,7 @@ where
     ///     );
     ///
     ///     // Update the user interface
-    ///     let messages = user_interface.update(events.drain(..));
+    ///     let messages = user_interface.update(&renderer, events.drain(..));
     ///
     ///     cache = user_interface.into_cache();
     ///
@@ -198,6 +198,7 @@ where
     /// ```
     pub fn update(
         &mut self,
+        renderer: &Renderer,
         events: impl Iterator<Item = Event>,
     ) -> Vec<Message> {
         let mut messages = Vec::new();
@@ -212,6 +213,7 @@ where
                 Layout::new(&self.layout),
                 self.cursor_position,
                 &mut messages,
+                renderer,
             );
         }
 
@@ -281,7 +283,7 @@ where
     ///         &mut renderer,
     ///     );
     ///
-    ///     let messages = user_interface.update(events.drain(..));
+    ///     let messages = user_interface.update(&renderer, events.drain(..));
     ///
     ///     // Draw the user interface
     ///     let mouse_cursor = user_interface.draw(&mut renderer);

native/src/widget.rs

@@ -117,6 +117,7 @@ where
         _layout: Layout<'_>,
         _cursor_position: Point,
         _messages: &mut Vec<Message>,
+        _renderer: &Renderer,
     ) {
     }
 }

native/src/widget/button.rs

@@ -31,6 +31,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        _renderer: &Renderer,
     ) {
         match event {
             Event::Mouse(mouse::Event::Input {

native/src/widget/checkbox.rs

@@ -20,6 +20,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        _renderer: &Renderer,
     ) {
         match event {
             Event::Mouse(mouse::Event::Input {

native/src/widget/column.rs

@@ -55,12 +55,17 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        renderer: &Renderer,
     ) {
         self.children.iter_mut().zip(layout.children()).for_each(
             |(child, layout)| {
-                child
-                    .widget
-                    .on_event(event, layout, cursor_position, messages)
+                child.widget.on_event(
+                    event,
+                    layout,
+                    cursor_position,
+                    messages,
+                    renderer,
+                )
             },
         );
     }

native/src/widget/radio.rs

@@ -21,6 +21,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        _renderer: &Renderer,
     ) {
         match event {
             Event::Mouse(mouse::Event::Input {

native/src/widget/row.rs

@@ -55,12 +55,17 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        renderer: &Renderer,
     ) {
         self.children.iter_mut().zip(layout.children()).for_each(
             |(child, layout)| {
-                child
-                    .widget
-                    .on_event(event, layout, cursor_position, messages)
+                child.widget.on_event(
+                    event,
+                    layout,
+                    cursor_position,
+                    messages,
+                    renderer,
+                )
             },
         );
     }

native/src/widget/scrollable.rs

@@ -46,6 +46,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        renderer: &Renderer,
     ) {
         let bounds = layout.bounds();
         let is_mouse_over = bounds.contains(cursor_position);
@@ -78,8 +79,13 @@ where
             Point::new(cursor_position.x, -1.0)
         };
 
-        self.content
-            .on_event(event, content, cursor_position, messages)
+        self.content.on_event(
+            event,
+            content,
+            cursor_position,
+            messages,
+            renderer,
+        )
     }
 
     fn draw(

native/src/widget/slider.rs

@@ -25,6 +25,7 @@ where
         layout: Layout<'_>,
         cursor_position: Point,
         messages: &mut Vec<Message>,
+        _renderer: &Renderer,
     ) {
         let mut change = || {
             let bounds = layout.bounds();

winit/src/application.rs

@@ -68,7 +68,8 @@ pub trait Application {
                     &renderer,
                 );
 
-                let messages = user_interface.update(events.drain(..));
+                let messages =
+                    user_interface.update(&renderer, events.drain(..));
 
                 if messages.is_empty() {
                     primitive = user_interface.draw(&mut renderer);