Introduce opaque widget helper

core/src/mouse/interaction.rs

@@ -3,6 +3,7 @@
 #[allow(missing_docs)]
 pub enum Interaction {
     #[default]
+    None,
     Idle,
     Pointer,
     Grab,

core/src/overlay.rs

@@ -79,7 +79,7 @@ where
         _viewport: &Rectangle,
         _renderer: &Renderer,
     ) -> mouse::Interaction {
-        mouse::Interaction::Idle
+        mouse::Interaction::None
     }
 
     /// Returns true if the cursor is over the [`Overlay`].

core/src/widget.rs

@@ -137,7 +137,7 @@ where
         _viewport: &Rectangle,
         _renderer: &Renderer,
     ) -> mouse::Interaction {
-        mouse::Interaction::Idle
+        mouse::Interaction::None
     }
 
     /// Returns the overlay of the [`Widget`], if there is any.

examples/loupe/src/main.rs

@@ -159,7 +159,7 @@ mod loupe {
             if cursor.is_over(layout.bounds()) {
                 mouse::Interaction::ZoomIn
             } else {
-                mouse::Interaction::Idle
+                mouse::Interaction::None
             }
         }
     }

runtime/src/multi_window/state.rs

@@ -48,7 +48,7 @@ where
             caches,
             queued_events: Vec::new(),
             queued_messages: Vec::new(),
-            mouse_interaction: mouse::Interaction::Idle,
+            mouse_interaction: mouse::Interaction::None,
         }
     }
 

runtime/src/program/state.rs

@@ -47,7 +47,7 @@ where
             cache,
             queued_events: Vec::new(),
             queued_messages: Vec::new(),
-            mouse_interaction: mouse::Interaction::Idle,
+            mouse_interaction: mouse::Interaction::None,
         }
     }
 

widget/src/helpers.rs

@@ -5,7 +5,7 @@ use crate::combo_box::{self, ComboBox};
 use crate::container::{self, Container};
 use crate::core;
 use crate::core::widget::operation;
-use crate::core::{Element, Length, Pixels};
+use crate::core::{Element, Length, Pixels, Widget};
 use crate::keyed;
 use crate::overlay;
 use crate::pick_list::{self, PickList};
@@ -123,6 +123,173 @@ where
     Stack::with_children(children)
 }
 
+/// Wraps the given widget and captures any mouse button presses inside the bounds of
+/// the widget—therefore making it _opaque_.
+///
+/// This helper is meant to be used to mark elements in a [`Stack`] to avoid mouse
+/// events from passing through layers.
+///
+/// [`Stack`]: crate::Stack
+pub fn opaque<'a, Message, Theme, Renderer>(
+    content: impl Into<Element<'a, Message, Theme, Renderer>>,
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: 'a,
+    Renderer: core::Renderer + 'a,
+{
+    use crate::core::event::{self, Event};
+    use crate::core::layout::{self, Layout};
+    use crate::core::mouse;
+    use crate::core::renderer;
+    use crate::core::widget::tree::{self, Tree};
+    use crate::core::{Rectangle, Shell, Size};
+
+    struct Opaque<'a, Message, Theme, Renderer> {
+        content: Element<'a, Message, Theme, Renderer>,
+    }
+
+    impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer>
+        for Opaque<'a, Message, Theme, Renderer>
+    where
+        Renderer: core::Renderer,
+    {
+        fn tag(&self) -> tree::Tag {
+            self.content.as_widget().tag()
+        }
+
+        fn state(&self) -> tree::State {
+            self.content.as_widget().state()
+        }
+
+        fn children(&self) -> Vec<Tree> {
+            self.content.as_widget().children()
+        }
+
+        fn diff(&self, tree: &mut Tree) {
+            self.content.as_widget().diff(tree);
+        }
+
+        fn size(&self) -> Size<Length> {
+            self.content.as_widget().size()
+        }
+
+        fn size_hint(&self) -> Size<Length> {
+            self.content.as_widget().size_hint()
+        }
+
+        fn layout(
+            &self,
+            tree: &mut Tree,
+            renderer: &Renderer,
+            limits: &layout::Limits,
+        ) -> layout::Node {
+            self.content.as_widget().layout(tree, renderer, limits)
+        }
+
+        fn draw(
+            &self,
+            tree: &Tree,
+            renderer: &mut Renderer,
+            theme: &Theme,
+            style: &renderer::Style,
+            layout: Layout<'_>,
+            cursor: mouse::Cursor,
+            viewport: &Rectangle,
+        ) {
+            self.content
+                .as_widget()
+                .draw(tree, renderer, theme, style, layout, cursor, viewport);
+        }
+
+        fn operate(
+            &self,
+            state: &mut Tree,
+            layout: Layout<'_>,
+            renderer: &Renderer,
+            operation: &mut dyn operation::Operation<Message>,
+        ) {
+            self.content
+                .as_widget()
+                .operate(state, layout, renderer, operation);
+        }
+
+        fn on_event(
+            &mut self,
+            state: &mut Tree,
+            event: Event,
+            layout: Layout<'_>,
+            cursor: mouse::Cursor,
+            renderer: &Renderer,
+            clipboard: &mut dyn core::Clipboard,
+            shell: &mut Shell<'_, Message>,
+            viewport: &Rectangle,
+        ) -> event::Status {
+            let is_mouse_press = matches!(
+                event,
+                core::Event::Mouse(mouse::Event::ButtonPressed(_))
+            );
+
+            if let core::event::Status::Captured =
+                self.content.as_widget_mut().on_event(
+                    state, event, layout, cursor, renderer, clipboard, shell,
+                    viewport,
+                )
+            {
+                return event::Status::Captured;
+            }
+
+            if is_mouse_press && cursor.is_over(layout.bounds()) {
+                event::Status::Captured
+            } else {
+                event::Status::Ignored
+            }
+        }
+
+        fn mouse_interaction(
+            &self,
+            state: &core::widget::Tree,
+            layout: core::Layout<'_>,
+            cursor: core::mouse::Cursor,
+            viewport: &core::Rectangle,
+            renderer: &Renderer,
+        ) -> core::mouse::Interaction {
+            let interaction = self
+                .content
+                .as_widget()
+                .mouse_interaction(state, layout, cursor, viewport, renderer);
+
+            if interaction == mouse::Interaction::None
+                && cursor.is_over(layout.bounds())
+            {
+                mouse::Interaction::Idle
+            } else {
+                interaction
+            }
+        }
+
+        fn overlay<'b>(
+            &'b mut self,
+            state: &'b mut core::widget::Tree,
+            layout: core::Layout<'_>,
+            renderer: &Renderer,
+            translation: core::Vector,
+        ) -> Option<core::overlay::Element<'b, Message, Theme, Renderer>>
+        {
+            self.content.as_widget_mut().overlay(
+                state,
+                layout,
+                renderer,
+                translation,
+            )
+        }
+    }
+
+    Element::new(Opaque {
+        content: content.into(),
+    })
+}
+
 /// Creates a new [`Scrollable`] with the provided content.
 ///
 /// [`Scrollable`]: crate::Scrollable

widget/src/image/viewer.rs

@@ -304,7 +304,7 @@ where
         } else if is_mouse_over {
             mouse::Interaction::Grab
         } else {
-            mouse::Interaction::Idle
+            mouse::Interaction::None
         }
     }
 

widget/src/mouse_area.rs

@@ -232,7 +232,7 @@ where
         );
 
         match (self.interaction, content_interaction) {
-            (Some(interaction), mouse::Interaction::Idle)
+            (Some(interaction), mouse::Interaction::None)
                 if cursor.is_over(layout.bounds()) =>
             {
                 interaction

widget/src/scrollable.rs

@@ -857,7 +857,7 @@ where
         if (mouse_over_x_scrollbar || mouse_over_y_scrollbar)
             || state.scrollers_grabbed()
         {
-            mouse::Interaction::Idle
+            mouse::Interaction::None
         } else {
             let translation =
                 state.translation(self.direction, bounds, content_bounds);

widget/src/stack.rs

@@ -249,7 +249,7 @@ where
                     state, layout, cursor, viewport, renderer,
                 )
             })
-            .find(|&interaction| interaction != mouse::Interaction::Idle)
+            .find(|&interaction| interaction != mouse::Interaction::None)
             .unwrap_or_default()
     }
 

winit/src/conversion.rs

@@ -396,7 +396,9 @@ pub fn mouse_interaction(
     use mouse::Interaction;
 
     match interaction {
-        Interaction::Idle => winit::window::CursorIcon::Default,
+        Interaction::None | Interaction::Idle => {
+            winit::window::CursorIcon::Default
+        }
         Interaction::Pointer => winit::window::CursorIcon::Pointer,
         Interaction::Working => winit::window::CursorIcon::Progress,
         Interaction::Grab => winit::window::CursorIcon::Grab,

winit/src/multi_window/window_manager.rs

@@ -60,7 +60,7 @@ where
                 exit_on_close_request,
                 surface,
                 renderer,
-                mouse_interaction: mouse::Interaction::Idle,
+                mouse_interaction: mouse::Interaction::None,
             },
         );