Make interactively moved window semitransparent

src/layout/mod.rs

@@ -93,6 +93,9 @@ pub const RESIZE_ANIMATION_THRESHOLD: f64 = 10.;
 /// Pointer needs to move this far to pull a window from the layout.
 const INTERACTIVE_MOVE_START_THRESHOLD: f64 = 256. * 256.;
 
+/// Opacity of interactively moved tiles targeting the scrolling layout.
+const INTERACTIVE_MOVE_ALPHA: f64 = 0.75;
+
 /// Size-relative units.
 pub struct SizeFrac;
 
@@ -2334,6 +2337,34 @@ impl<W: LayoutElement> Layout<W> {
                     // Tile position must be rounded to physical pixels.
                     assert_abs_diff_eq!(tile_pos.x, rounded_pos.x, epsilon = 1e-5);
                     assert_abs_diff_eq!(tile_pos.y, rounded_pos.y, epsilon = 1e-5);
+
+                    if let Some(alpha) = &move_.tile.alpha_animation {
+                        if move_.is_floating {
+                            assert_eq!(
+                                alpha.anim.to(),
+                                1.,
+                                "interactively moved floating tile can animate alpha only to 1"
+                            );
+
+                            assert!(
+                                !alpha.hold_after_done,
+                                "interactively moved floating tile \
+                                 cannot have held alpha animation"
+                            );
+                        } else {
+                            assert_ne!(
+                                alpha.anim.to(),
+                                1.,
+                                "interactively moved scrolling tile must animate alpha to not 1"
+                            );
+
+                            assert!(
+                                alpha.hold_after_done,
+                                "interactively moved scrolling tile \
+                                 must have held alpha animation"
+                            );
+                        }
+                    }
                 }
             }
         }
@@ -3005,6 +3036,21 @@ impl<W: LayoutElement> Layout<W> {
                     size.h = ensure_min_max_size_maybe_zero(size.h, min_size.h, max_size.h);
 
                     win.request_size_once(size, true);
+
+                    // Animate the tile back to opaque.
+                    move_.tile.animate_alpha(
+                        INTERACTIVE_MOVE_ALPHA,
+                        1.,
+                        self.options.animations.window_movement.0,
+                    );
+                } else {
+                    // Animate the tile back to semitransparent.
+                    move_.tile.animate_alpha(
+                        1.,
+                        INTERACTIVE_MOVE_ALPHA,
+                        self.options.animations.window_movement.0,
+                    );
+                    move_.tile.hold_alpha_animation_after_done();
                 }
 
                 return;
@@ -3773,6 +3819,16 @@ impl<W: LayoutElement> Layout<W> {
                     is_floating = unfullscreen_to_floating;
                 }
 
+                // Animate to semitransparent.
+                if !is_floating {
+                    tile.animate_alpha(
+                        1.,
+                        INTERACTIVE_MOVE_ALPHA,
+                        self.options.animations.window_movement.0,
+                    );
+                    tile.hold_alpha_animation_after_done();
+                }
+
                 let mut data = InteractiveMoveData {
                     tile,
                     output,
@@ -3869,7 +3925,7 @@ impl<W: LayoutElement> Layout<W> {
             return;
         }
 
-        let Some(InteractiveMoveState::Moving(move_)) = self.interactive_move.take() else {
+        let Some(InteractiveMoveState::Moving(mut move_)) = self.interactive_move.take() else {
             unreachable!()
         };
 
@@ -3878,6 +3934,13 @@ impl<W: LayoutElement> Layout<W> {
             for ws in self.workspaces_mut() {
                 ws.dnd_scroll_gesture_end();
             }
+
+            // Also animate the tile back to opaque.
+            move_.tile.animate_alpha(
+                INTERACTIVE_MOVE_ALPHA,
+                1.,
+                self.options.animations.window_movement.0,
+            );
         }
 
         match &mut self.monitor_set {

src/layout/tile.rs

@@ -148,6 +148,12 @@ struct MoveAnimation {
 #[derive(Debug)]
 pub(super) struct AlphaAnimation {
     pub(super) anim: Animation,
+    /// Whether the animation should persist after it's done.
+    ///
+    /// This is used by things like interactive move which need to animate alpha to
+    /// semitransparent, then hold it at semitransparent for a while, until the operation
+    /// completes.
+    pub(super) hold_after_done: bool,
     offscreen: OffscreenBuffer,
 }
 
@@ -319,7 +325,7 @@ impl<W: LayoutElement> Tile<W> {
         }
 
         if let Some(alpha) = &mut self.alpha_animation {
-            if alpha.anim.is_done() {
+            if !alpha.hold_after_done && alpha.anim.is_done() {
                 self.alpha_animation = None;
             }
         }
@@ -334,7 +340,10 @@ impl<W: LayoutElement> Tile<W> {
             || self.resize_animation.is_some()
             || self.move_x_animation.is_some()
             || self.move_y_animation.is_some()
-            || self.alpha_animation.is_some()
+            || self
+                .alpha_animation
+                .as_ref()
+                .is_some_and(|alpha| !alpha.anim.is_done())
     }
 
     pub fn update_render_elements(&mut self, is_active: bool, view_rect: Rectangle<f64, Logical>) {
@@ -491,6 +500,7 @@ impl<W: LayoutElement> Tile<W> {
 
         self.alpha_animation = Some(AlphaAnimation {
             anim: Animation::new(self.clock.clone(), current, to, 0., config),
+            hold_after_done: false,
             offscreen,
         });
     }
@@ -505,6 +515,12 @@ impl<W: LayoutElement> Tile<W> {
         }
     }
 
+    pub fn hold_alpha_animation_after_done(&mut self) {
+        if let Some(alpha) = &mut self.alpha_animation {
+            alpha.hold_after_done = true;
+        }
+    }
+
     pub fn window(&self) -> &W {
         &self.window
     }

src/layout/workspace.rs

@@ -1757,6 +1757,11 @@ impl<W: LayoutElement> Workspace<W> {
                 if visible {
                     assert_eq!(anim.to(), 1., "visible tiles can animate alpha only to 1");
                 }
+
+                assert!(
+                    !alpha.hold_after_done,
+                    "tiles in the layout cannot have held alpha animation"
+                );
             }
         }
     }