Draft `Scrollable` widget (no clipping yet!)

3 files changed, 125 insertions, 1 deletions

diff --git a/native/src/user_interface.rs b/native/src/user_interface.rs
index 5675076d..5df0dc6a 100644
--- a/native/src/user_interface.rs
+++ b/native/src/user_interface.rs
@@ -347,7 +347,7 @@ impl Cache {
                 .0
                 .compute_layout(geometry::Size::undefined())
                 .unwrap(),
-            cursor_position: Point::new(0.0, 0.0),
+            cursor_position: Point::new(-1.0, -1.0),
         }
     }
 }
diff --git a/native/src/widget.rs b/native/src/widget.rs
index bcef2665..0d3f6d2c 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -26,6 +26,7 @@ pub mod column;
 pub mod image;
 pub mod radio;
 pub mod row;
+pub mod scrollable;
 pub mod slider;
 pub mod text;
 
@@ -42,6 +43,8 @@ pub use radio::Radio;
 #[doc(no_inline)]
 pub use row::Row;
 #[doc(no_inline)]
+pub use scrollable::Scrollable;
+#[doc(no_inline)]
 pub use slider::Slider;
 #[doc(no_inline)]
 pub use text::Text;
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
new file mode 100644
index 00000000..4644282b
--- /dev/null
+++ b/native/src/widget/scrollable.rs
@@ -0,0 +1,121 @@
+use crate::{
+    column, input::mouse, Element, Event, Hasher, Layout, Node, Point, Style,
+    Widget,
+};
+
+pub use iced_core::scrollable::State;
+
+/// A scrollable [`Column`].
+///
+/// [`Column`]: ../column/struct.Column.html
+pub type Scrollable<'a, Message, Renderer> =
+    iced_core::Scrollable<'a, Element<'a, Message, Renderer>>;
+
+impl<'a, Message, Renderer> Widget<Message, Renderer>
+    for Scrollable<'a, Message, Renderer>
+where
+    Renderer: self::Renderer + column::Renderer,
+{
+    fn node(&self, renderer: &Renderer) -> Node {
+        let mut content = self.content.node(renderer);
+
+        {
+            let mut style = content.0.style();
+            style.flex_shrink = 0.0;
+
+            content.0.set_style(style);
+        }
+
+        let mut style = Style::default()
+            .width(self.content.width)
+            .max_width(self.content.max_width)
+            .height(self.height)
+            .align_self(self.align_self)
+            .align_items(self.align_items);
+
+        style.0.flex_direction = stretch::style::FlexDirection::Column;
+
+        Node::with_children(style, vec![content])
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+    ) {
+        let bounds = layout.bounds();
+        let is_mouse_over = bounds.contains(cursor_position);
+
+        let content = layout.children().next().unwrap();
+        let content_bounds = content.bounds();
+
+        if is_mouse_over {
+            match event {
+                Event::Mouse(mouse::Event::WheelScrolled {
+                    delta_y, ..
+                }) => {
+                    // TODO: Configurable speed (?)
+                    self.state.offset = (self.state.offset as i32
+                        - delta_y.round() as i32 * 15)
+                        .max(0)
+                        .min((content_bounds.height - bounds.height) as i32)
+                        as u32;
+                }
+                _ => {}
+            }
+        }
+
+        let cursor_position = if is_mouse_over {
+            Point::new(
+                cursor_position.x,
+                cursor_position.y + self.state.offset as f32,
+            )
+        } else {
+            Point::new(cursor_position.x, -1.0)
+        };
+
+        self.content.on_event(
+            event,
+            layout.children().next().unwrap(),
+            cursor_position,
+            messages,
+        )
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output {
+        self::Renderer::draw(renderer, &self, layout, cursor_position)
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        self.content.hash_layout(state)
+    }
+}
+
+pub trait Renderer: crate::Renderer + Sized {
+    fn draw<Message>(
+        &mut self,
+        scrollable: &Scrollable<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Self::Output;
+}
+
+impl<'a, Message, Renderer> From<Scrollable<'a, Message, Renderer>>
+    for Element<'a, Message, Renderer>
+where
+    Renderer: 'a + self::Renderer + column::Renderer,
+    Message: 'static,
+{
+    fn from(
+        scrollable: Scrollable<'a, Message, Renderer>,
+    ) -> Element<'a, Message, Renderer> {
+        Element::new(scrollable)
+    }
+}