Provide Renderer to Widget::on_event

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

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();