Draft Scrollable widget (no clipping yet!)

wgpu/src/renderer/scrollable.rs

@@ -0,0 +1,70 @@
+use crate::{Primitive, Renderer};
+use iced_native::{
+    scrollable, Background, Color, Layout, Point, Rectangle, Scrollable, Widget,
+};
+
+impl scrollable::Renderer for Renderer {
+    fn draw<Message>(
+        &mut self,
+        scrollable: &Scrollable<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Self::Output {
+        let bounds = layout.bounds();
+        let is_mouse_over = bounds.contains(cursor_position);
+
+        let content = layout.children().next().unwrap();
+        let content_bounds = content.bounds();
+
+        let cursor_position = if bounds.contains(cursor_position) {
+            Point::new(
+                cursor_position.x,
+                cursor_position.y + scrollable.state.offset as f32,
+            )
+        } else {
+            Point::new(cursor_position.x, -1.0)
+        };
+
+        let (content, mouse_cursor) =
+            scrollable.content.draw(self, content, cursor_position);
+
+        let primitive = Primitive::Scrollable {
+            bounds,
+            offset: scrollable.state.offset,
+            content: Box::new(content),
+        };
+
+        (
+            Primitive::Group {
+                primitives: if is_mouse_over
+                    && content_bounds.height > bounds.height
+                {
+                    let ratio = bounds.height / content_bounds.height;
+                    let scrollbar_height = bounds.height * ratio;
+                    let y_offset = scrollable.state.offset as f32 * ratio;
+
+                    let scrollbar = Primitive::Quad {
+                        bounds: Rectangle {
+                            x: bounds.x + bounds.width - 12.0,
+                            y: bounds.y + y_offset,
+                            width: 10.0,
+                            height: scrollbar_height,
+                        },
+                        background: Background::Color(Color {
+                            r: 0.0,
+                            g: 0.0,
+                            b: 0.0,
+                            a: 0.5,
+                        }),
+                        border_radius: 5,
+                    };
+
+                    vec![primitive, scrollbar]
+                } else {
+                    vec![primitive]
+                },
+            },
+            mouse_cursor,
+        )
+    }
+}