Workspaces in multitasking view should not animate as if they are stacked (#1002)

src/Widgets/MultitaskingView.vala

@@ -300,7 +300,6 @@ namespace Gala {
          *                positions immediately.
          */
         void update_positions (bool animate) {
-            var scale = InternalUtils.get_ui_scaling_factor ();
 #if HAS_MUTTER330
             unowned Meta.WorkspaceManager manager = display.get_workspace_manager ();
             var active_index = manager.get_active_workspace ().index ();
@@ -312,7 +311,7 @@ namespace Gala {
             foreach (var child in workspaces.get_children ()) {
                 unowned WorkspaceClone workspace_clone = (WorkspaceClone) child;
                 var index = workspace_clone.workspace.index ();
-                var dest_x = index * (workspace_clone.width - (150 * scale));
+                var dest_x = workspace_clone.multitasking_view_x ();
 
                 if (index == active_index) {
                     active_x = dest_x;
@@ -647,7 +646,9 @@ namespace Gala {
                 child.remove_all_transitions ();
             }
 
-            update_positions (false);
+            if (!gesture_animation_director.canceling) {
+                update_positions (false);
+            }
 
             foreach (var child in workspaces.get_children ()) {
                 unowned WorkspaceClone workspace = (WorkspaceClone) child;

src/Widgets/WorkspaceClone.vala

@@ -128,6 +128,12 @@ namespace Gala {
          */
         const int HOVER_ACTIVATE_DELAY = 400;
 
+        /**
+         * The MultitaskingView shows the workspaces overlapping them WorkspaceClone.X_OFFSET pixels
+         * making it possible to move windows to the next/previous workspace.
+         */
+         public const int X_OFFSET = 150;
+
         /**
          * A window has been selected, the MultitaskingView should consider activating
          * and closing the view.
@@ -350,6 +356,35 @@ namespace Gala {
             }
         }
 
+        /**
+         * @return The position on the X axis of this workspace.
+         */
+        public float multitasking_view_x () {
+            var scale_factor = InternalUtils.get_ui_scaling_factor ();
+            return workspace.index () * (width - (X_OFFSET * scale_factor));
+        }
+
+        /**
+         * @return The amount of pixels the workspace is overlapped in the X axis.
+         */
+        float current_x_overlap () {
+            var scale_factor = InternalUtils.get_ui_scaling_factor ();
+#if HAS_MUTTER330
+            var display = workspace.get_display ();
+            unowned Meta.WorkspaceManager manager = display.get_workspace_manager ();
+            var active_index = manager.get_active_workspace ().index ();
+#else
+            var screen = workspace.get_screen ();
+            var active_index = screen.get_active_workspace ().index ();
+#endif
+            if (workspace.index () == active_index) {
+                return 0;
+            } else {
+                var x_offset = X_OFFSET * scale_factor + WindowManagerGala.WORKSPACE_GAP;
+                return (workspace.index () < active_index) ? -x_offset : x_offset;
+            }
+        }
+
         /**
          * Utility function to shrink a MetaRectangle on all sides for the given amount.
          * Negative amounts will scale it instead.
@@ -387,16 +422,23 @@ namespace Gala {
 
             var monitor = screen.get_monitor_geometry (screen.get_primary_monitor ());
 #endif
+            var initial_x = gesture_animation_director.canceling ? x : x + current_x_overlap ();
+            var target_x = multitasking_view_x ();
+
             var scale = (float)(monitor.height - TOP_OFFSET * scale_factor - BOTTOM_OFFSET * scale_factor) / monitor.height;
             var pivotY = TOP_OFFSET * scale_factor / (monitor.height - monitor.height * scale);
 
             update_size (monitor);
 
             GestureAnimationDirector.OnBegin on_animation_begin = () => {
+                x = initial_x;
                 background.set_pivot_point (0.5f, pivotY);
             };
 
             GestureAnimationDirector.OnUpdate on_animation_update = (percentage) => {
+                var x = GestureAnimationDirector.animation_value (initial_x, target_x, percentage);
+                set_x (x);
+
                 double update_scale = (double)GestureAnimationDirector.animation_value (1.0f, (float)scale, percentage);
                 background.set_scale (update_scale, update_scale);
             };
@@ -406,6 +448,12 @@ namespace Gala {
                     return;
                 }
 
+                save_easing_state ();
+                set_easing_duration (MultitaskingView.ANIMATION_DURATION);
+                set_easing_mode (MultitaskingView.ANIMATION_MODE);
+                set_x (target_x);
+                restore_easing_state ();
+
                 background.save_easing_state ();
                 background.set_easing_duration (MultitaskingView.ANIMATION_DURATION);
                 background.set_easing_mode (MultitaskingView.ANIMATION_MODE);
@@ -453,10 +501,16 @@ namespace Gala {
 
             opened = false;
 
+            var initial_x = gesture_animation_director.canceling ? x : multitasking_view_x ();
+            var target_x = multitasking_view_x () + current_x_overlap ();
+
             double initial_scale_x, initial_scale_y;
             background.get_scale (out initial_scale_x, out initial_scale_y);
 
             GestureAnimationDirector.OnUpdate on_animation_update = (percentage) => {
+                var x = GestureAnimationDirector.animation_value (initial_x, target_x, percentage);
+                set_x (x);
+
                 double scale_x = (double) GestureAnimationDirector.animation_value ((float) initial_scale_x, 1.0f, percentage);
                 double scale_y = (double) GestureAnimationDirector.animation_value ((float) initial_scale_y, 1.0f, percentage);
                 background.set_scale (scale_x, scale_y);
@@ -467,6 +521,12 @@ namespace Gala {
                     return;
                 }
 
+                save_easing_state ();
+                set_easing_duration (MultitaskingView.ANIMATION_DURATION);
+                set_easing_mode (MultitaskingView.ANIMATION_MODE);
+                set_x (target_x);
+                restore_easing_state ();
+
                 background.save_easing_state ();
                 background.set_easing_duration (MultitaskingView.ANIMATION_DURATION);
                 background.set_easing_mode (MultitaskingView.ANIMATION_MODE);

src/WindowManager.vala

@@ -102,7 +102,10 @@ namespace Gala {
         private bool animating_switch_workspace = false;
         private GestureAnimationDirector gesture_animation_director;
 
-        private const int WORKSPACE_GAP = 24;
+        /**
+         * Gap to show between workspaces while switching between them.
+         */
+        public const int WORKSPACE_GAP = 24;
 
         construct {
             gesture_animation_director = new GestureAnimationDirector ();