Introduce `Levitating` variant for `mouse::Cursor`

3 files changed, 45 insertions, 21 deletions

diff --git a/core/src/mouse/cursor.rs b/core/src/mouse/cursor.rs
index 616cd315..9388a578 100644
--- a/core/src/mouse/cursor.rs
+++ b/core/src/mouse/cursor.rs
@@ -1,13 +1,14 @@
 use crate::{Point, Rectangle, Transformation, Vector};
 
-use std::ops::Mul;
-
 /// The mouse cursor state.
 #[derive(Debug, Clone, Copy, PartialEq, Default)]
 pub enum Cursor {
     /// The cursor has a defined position.
     Available(Point),
 
+    /// The cursor has a defined position, but it's levitating over a layer above.
+    Levitating(Point),
+
     /// The cursor is currently unavailable (i.e. out of bounds or busy).
     #[default]
     Unavailable,
@@ -18,7 +19,7 @@ impl Cursor {
     pub fn position(self) -> Option<Point> {
         match self {
             Cursor::Available(position) => Some(position),
-            Cursor::Unavailable => None,
+            Cursor::Levitating(_) | Cursor::Unavailable => None,
         }
     }
 
@@ -51,17 +52,41 @@ impl Cursor {
     pub fn is_over(self, bounds: Rectangle) -> bool {
         self.position_over(bounds).is_some()
     }
+
+    /// Returns true if the [`Cursor`] is levitating over a layer above.
+    pub fn is_levitating(self) -> bool {
+        matches!(self, Self::Levitating(_))
+    }
+
+    /// Makes the [`Cursor`] levitate over a layer above.
+    pub fn levitate(self) -> Self {
+        match self {
+            Self::Available(position) => Self::Levitating(position),
+            _ => self,
+        }
+    }
+
+    /// Brings the [`Cursor`] back to the current layer.
+    pub fn land(self) -> Self {
+        match self {
+            Cursor::Levitating(position) => Cursor::Available(position),
+            _ => self,
+        }
+    }
 }
 
-impl Mul<Transformation> for Cursor {
+impl std::ops::Mul<Transformation> for Cursor {
     type Output = Self;
 
     fn mul(self, transformation: Transformation) -> Self {
         match self {
-            Cursor::Unavailable => Cursor::Unavailable,
-            Cursor::Available(point) => {
-                Cursor::Available(point * transformation)
+            Self::Available(position) => {
+                Self::Available(position * transformation)
+            }
+            Self::Levitating(position) => {
+                Self::Levitating(position * transformation)
             }
+            Self::Unavailable => Self::Unavailable,
         }
     }
 }
diff --git a/widget/src/scrollable.rs b/widget/src/scrollable.rs
index 312aee29..2dbe0479 100644
--- a/widget/src/scrollable.rs
+++ b/widget/src/scrollable.rs
@@ -563,7 +563,8 @@ where
                     Event::Mouse(mouse::Event::CursorMoved { .. })
                     | Event::Touch(touch::Event::FingerMoved { .. }) => {
                         if let Some(scrollbar) = scrollbars.y {
-                            let Some(cursor_position) = cursor.position()
+                            let Some(cursor_position) =
+                                cursor.land().position()
                             else {
                                 return;
                             };
@@ -635,7 +636,8 @@ where
                 match event {
                     Event::Mouse(mouse::Event::CursorMoved { .. })
                     | Event::Touch(touch::Event::FingerMoved { .. }) => {
-                        let Some(cursor_position) = cursor.position() else {
+                        let Some(cursor_position) = cursor.land().position()
+                        else {
                             return;
                         };
 
diff --git a/widget/src/stack.rs b/widget/src/stack.rs
index 12ed941d..d5cf1ecf 100644
--- a/widget/src/stack.rs
+++ b/widget/src/stack.rs
@@ -216,15 +216,15 @@ where
         viewport: &Rectangle,
     ) {
         let is_over = cursor.is_over(layout.bounds());
-        let is_mouse_movement =
-            matches!(event, Event::Mouse(mouse::Event::CursorMoved { .. }));
+        let end = self.children.len() - 1;
 
-        for ((child, state), layout) in self
+        for (i, ((child, state), layout)) in self
             .children
             .iter_mut()
             .rev()
             .zip(tree.children.iter_mut().rev())
             .zip(layout.children().rev())
+            .enumerate()
         {
             child.as_widget_mut().update(
                 state,
@@ -237,22 +237,19 @@ where
                 viewport,
             );
 
-            if is_over
-                && !is_mouse_movement
-                && cursor != mouse::Cursor::Unavailable
-            {
+            if shell.is_event_captured() {
+                return;
+            }
+
+            if i < end && is_over && !cursor.is_levitating() {
                 let interaction = child.as_widget().mouse_interaction(
                     state, layout, cursor, viewport, renderer,
                 );
 
                 if interaction != mouse::Interaction::None {
-                    cursor = mouse::Cursor::Unavailable;
+                    cursor = cursor.levitate();
                 }
             }
-
-            if shell.is_event_captured() {
-                return;
-            }
         }
     }