MultitaskingView: Allow workspace switch animation to be interrupted

src/Gestures/GesturePropertyTransition.vala

@@ -88,35 +88,55 @@ public class Gala.GesturePropertyTransition : Object {
      * be set immediately on {@link GestureTracker.OnEnd} not only once the animation ends to allow for interrupting the animation by starting a new gesture.
      * done_callback will only be called if the animation finishes, not if it is interrupted e.g. by starting a new animation for the same property,
      * destroying the actor or removing the transition.
+     *
+     * @return If a transition is currently in progress for the actor and the property the percentage how far the current value
+     * is towards the to_value given the final value of the ongoing transition is returned. This is usally the case if a gesture ended but was
+     * started again before the animation finished so this should be used to set {@link GestureTracker.initial_percentage}. If no transition
+     * is in progress 0 is returned.
      */
-    public void start (bool with_gesture, owned DoneCallback? done_callback = null) {
+    public double start (bool with_gesture, owned DoneCallback? done_callback = null) {
         ref ();
 
         this.done_callback = (owned) done_callback;
 
         Value current_value = {};
         actor.get_property (property, ref current_value);
 
-        actual_from_value = from_value ?? current_value;
+        Value initial_value;
+
+        unowned var old_transition = actor.get_transition (property);
+        if (old_transition != null) {
+            initial_value = old_transition.interval.final;
+        } else {
+            initial_value = current_value;
+        }
+
+        actual_from_value = from_value ?? initial_value;
 
         if (actual_from_value.type () != current_value.type ()) {
             warning ("from_value of type %s is not of the same type as the property %s which is %s. Can't animate.", from_value.type_name (), property, current_value.type_name ());
             finish ();
-            return;
+            return 0;
         }
 
         if (current_value.type () != to_value.type ()) {
             warning ("to_value of type %s is not of the same type as the property %s which is %s. Can't animate.", to_value.type_name (), property, current_value.type_name ());
             finish ();
-            return;
+            return 0;
         }
 
         // Pre calculate some things, so we don't have to do it on every update
         from_value_float = value_to_float (actual_from_value);
         to_value_float = value_to_float (to_value);
 
-        GestureTracker.OnBegin on_animation_begin = () => {
-            actor.set_property (property, actual_from_value);
+        var current_value_double = (double) value_to_float (current_value);
+        var initial_value_double = (double) value_to_float (initial_value);
+
+        var initial_percentage = ((to_value_float - initial_value_double) - (to_value_float - current_value_double)) / (to_value_float - initial_value_double);
+
+        GestureTracker.OnBegin on_animation_begin = (percentage) => {
+            var animation_value = GestureTracker.animation_value (from_value_float, to_value_float, percentage, false);
+            actor.set_property (property, value_from_float (animation_value));
         };
 
         GestureTracker.OnUpdate on_animation_update = (percentage) => {
@@ -180,6 +200,8 @@ public class Gala.GesturePropertyTransition : Object {
                 on_animation_end (1, 1, gesture_tracker.min_animation_duration);
             }
         }
+
+        return initial_percentage;
     }
 
     private void finish (bool callback = true) {

src/Gestures/GestureTracker.vala

@@ -95,8 +95,10 @@ public class Gala.GestureTracker : Object {
      * start receiving updates.
      * @param gesture the same gesture as in {@link on_gesture_detected}
      * @param timestamp the timestamp of the event that initiated the gesture or {@link Meta.CURRENT_TIME}.
+     * @return the initial percentage that should already be preapplied. This is useful
+     * if an animation was still ongoing when the gesture was started.
      */
-    public signal void on_gesture_handled (Gesture gesture, uint32 timestamp);
+    public signal double on_gesture_handled (Gesture gesture, uint32 timestamp);
 
     /**
      * Emitted right after on_gesture_detected with the initial gesture information.
@@ -135,19 +137,25 @@ public class Gala.GestureTracker : Object {
 
     private Gee.ArrayList<ulong> handlers;
 
+    private double applied_percentage;
     private double previous_percentage;
     private uint64 previous_time;
-    private double percentage_delta;
+    private double previous_delta;
     private double velocity;
+    // Used to check whether to cancel. Necessary because on_end is often called
+    // with the same percentage as the last update so this is the one before the last update.
+    private double old_previous;
 
     construct {
         settings = new GestureSettings ();
 
         handlers = new Gee.ArrayList<ulong> ();
+        applied_percentage = 0;
         previous_percentage = 0;
         previous_time = 0;
-        percentage_delta = 0;
+        previous_delta = 0;
         velocity = 0;
+        old_previous = 0;
     }
 
     public GestureTracker (int min_animation_duration, int max_animation_duration) {
@@ -249,7 +257,7 @@ public class Gala.GestureTracker : Object {
     private bool gesture_detected (GestureBackend backend, Gesture gesture, uint32 timestamp) {
         if (enabled && on_gesture_detected (gesture)) {
             backend.prepare_gesture_handling ();
-            on_gesture_handled (gesture, timestamp);
+            applied_percentage = on_gesture_handled (gesture, timestamp);
             return true;
         }
 
@@ -258,7 +266,7 @@ public class Gala.GestureTracker : Object {
 
     private void gesture_begin (double percentage, uint64 elapsed_time) {
         if (enabled) {
-            on_begin (percentage);
+            on_begin (applied_percentage);
         }
 
         recognizing = true;
@@ -267,6 +275,7 @@ public class Gala.GestureTracker : Object {
     }
 
     private void gesture_update (double percentage, uint64 elapsed_time) {
+        var updated_delta = previous_delta;
         if (elapsed_time != previous_time) {
             double distance = percentage - previous_percentage;
             double time = (double)(elapsed_time - previous_time);
@@ -275,43 +284,59 @@ public class Gala.GestureTracker : Object {
             if (velocity > MAX_VELOCITY) {
                 velocity = MAX_VELOCITY;
                 var used_percentage = MAX_VELOCITY * time + previous_percentage;
-                percentage_delta += percentage - used_percentage;
+                updated_delta += percentage - used_percentage;
             }
         }
 
+        applied_percentage += calculate_applied_delta (percentage, updated_delta);
+
         if (enabled) {
-            on_update (applied_percentage (percentage, percentage_delta));
+            on_update (applied_percentage);
         }
 
+        old_previous = previous_percentage;
         previous_percentage = percentage;
         previous_time = elapsed_time;
+        previous_delta = updated_delta;
     }
 
     private void gesture_end (double percentage, uint64 elapsed_time) {
-        double end_percentage = applied_percentage (percentage, percentage_delta);
-        int completions = (int) end_percentage;
-        bool cancel_action = (end_percentage.abs () < SUCCESS_PERCENTAGE_THRESHOLD)
-            && ((end_percentage.abs () <= previous_percentage.abs ()) && (velocity < SUCCESS_VELOCITY_THRESHOLD));
-        int calculated_duration = calculate_end_animation_duration (end_percentage, cancel_action);
+        applied_percentage += calculate_applied_delta (percentage, previous_delta);
+
+        int completions = (int) applied_percentage;
+
+        var remaining_percentage = applied_percentage - completions;
+
+        bool cancel_action = ((percentage - completions).abs () < SUCCESS_PERCENTAGE_THRESHOLD) && (velocity.abs () < SUCCESS_VELOCITY_THRESHOLD)
+            || ((percentage.abs () < old_previous.abs ()) && (velocity.abs () > SUCCESS_VELOCITY_THRESHOLD));
+
+        int calculated_duration = calculate_end_animation_duration (remaining_percentage, cancel_action);
 
         if (!cancel_action) {
-            completions += end_percentage < 0 ? -1 : 1;
+            completions += applied_percentage < 0 ? -1 : 1;
         }
 
         if (enabled) {
-            on_end (end_percentage, completions, calculated_duration);
+            on_end (applied_percentage, completions, calculated_duration);
         }
 
         disconnect_all_handlers ();
         recognizing = false;
+        applied_percentage = 0;
         previous_percentage = 0;
         previous_time = 0;
-        percentage_delta = 0;
+        previous_delta = 0;
         velocity = 0;
+        old_previous = 0;
     }
 
-    private static inline double applied_percentage (double percentage, double percentage_delta) {
-        return percentage - percentage_delta;
+    /**
+     * Calculate the delta between the new percentage and the previous one while taking into account
+     * the velocity delta which makes sure we don't go over the MAX_VELOCITY. The velocity delta we use
+     * for the calculation shouldn't be confused with this delta.
+     */
+    private inline double calculate_applied_delta (double percentage, double percentage_delta) {
+        return (percentage - percentage_delta) - (previous_percentage - previous_delta);
     }
 
     /**

src/Widgets/MultitaskingView.vala

@@ -47,11 +47,6 @@ namespace Gala {
         private Drawing.StyleManager style_manager;
 
         private bool switching_workspace_with_gesture = false;
-        private bool switching_workspace_in_progress {
-            get {
-                return switching_workspace_with_gesture || workspaces.get_transition ("x") != null;
-            }
-        }
 
         public MultitaskingView (WindowManagerGala wm) {
             Object (wm: wm);
@@ -71,7 +66,7 @@ namespace Gala {
             multitasking_gesture_tracker = new GestureTracker (ANIMATION_DURATION, ANIMATION_DURATION);
             multitasking_gesture_tracker.enable_touchpad ();
             multitasking_gesture_tracker.on_gesture_detected.connect (on_multitasking_gesture_detected);
-            multitasking_gesture_tracker.on_gesture_handled.connect (() => toggle (true, false));
+            multitasking_gesture_tracker.on_gesture_handled.connect (on_multitasking_gesture_handled);
 
             workspace_gesture_tracker = new GestureTracker (AnimationDuration.WORKSPACE_SWITCH_MIN, AnimationDuration.WORKSPACE_SWITCH);
             workspace_gesture_tracker.enable_touchpad ();
@@ -304,6 +299,11 @@ namespace Gala {
             return false;
         }
 
+        private double on_multitasking_gesture_handled (Gesture gesture, uint32 timestamp) {
+            toggle (true, false);
+            return 0;
+        }
+
         private bool on_workspace_gesture_detected (Gesture gesture) {
             if (!opened) {
                 return false;
@@ -316,11 +316,7 @@ namespace Gala {
             return false;
         }
 
-        private void switch_workspace_with_gesture (Gesture gesture, uint32 timestamp) {
-            if (switching_workspace_in_progress) {
-                return;
-            }
-
+        private double switch_workspace_with_gesture (Gesture gesture, uint32 timestamp) {
             var direction = workspace_gesture_tracker.settings.get_natural_scroll_direction (gesture);
 
             unowned var manager = display.get_workspace_manager ();
@@ -364,7 +360,7 @@ namespace Gala {
             var upper_clamp = (direction == LEFT) ? (active_workspace.index () + 0.1) : (num_workspaces - active_workspace.index () - 0.9);
             var lower_clamp = (direction == RIGHT) ? - (active_workspace.index () + 0.1) : - (num_workspaces - active_workspace.index () - 0.9);
 
-            new GesturePropertyTransition (workspaces, workspace_gesture_tracker, "x", null, target_x) {
+            var initial_percentage = new GesturePropertyTransition (workspaces, workspace_gesture_tracker, "x", null, target_x) {
                 overshoot_lower_clamp = lower_clamp,
                 overshoot_upper_clamp = upper_clamp
             }.start (true);
@@ -381,6 +377,8 @@ namespace Gala {
             } else {
                 workspace_gesture_tracker.connect_handlers (null, null, (owned) on_animation_end);
             }
+
+            return initial_percentage;
         }
 
         /**

src/WindowManager.vala

@@ -596,7 +596,7 @@ namespace Gala {
             return switch_workspace_with_gesture || (action == SWITCH_WINDOWS && !window_switcher.opened);
         }
 
-        private void on_gesture_handled (Gesture gesture, uint32 timestamp) {
+        private double on_gesture_handled (Gesture gesture, uint32 timestamp) {
             var direction = gesture_tracker.settings.get_natural_scroll_direction (gesture);
 
             switch (GestureSettings.get_action (gesture)) {
@@ -620,6 +620,8 @@ namespace Gala {
                 default:
                     break;
             }
+
+            return 0;
         }
 
         /**

src/Zoom.vala

@@ -33,7 +33,7 @@ public class Gala.Zoom : Object {
         gesture_tracker = new GestureTracker (ANIMATION_DURATION, ANIMATION_DURATION);
         gesture_tracker.enable_touchpad ();
         gesture_tracker.on_gesture_detected.connect (on_gesture_detected);
-        gesture_tracker.on_gesture_handled.connect ((gesture) => zoom_with_gesture (gesture.direction));
+        gesture_tracker.on_gesture_handled.connect (on_gesture_handled);
 
         behavior_settings = new GLib.Settings ("io.elementary.desktop.wm.behavior");
 
@@ -101,9 +101,9 @@ public class Gala.Zoom : Object {
         return Clutter.EVENT_STOP;
     }
 
-    private void zoom_with_gesture (GestureDirection direction) {
+    private double on_gesture_handled (Gesture gesture, uint32 timestamp) {
         var initial_zoom = current_zoom;
-        var target_zoom = (direction == GestureDirection.IN)
+        var target_zoom = (gesture.direction == GestureDirection.IN)
             ? initial_zoom - MAX_ZOOM
             : initial_zoom + MAX_ZOOM;
 
@@ -123,6 +123,8 @@ public class Gala.Zoom : Object {
         };
 
         gesture_tracker.connect_handlers (null, (owned) on_animation_update, null);
+
+        return 0;
     }
 
     private inline Graphene.Point compute_new_pivot_point () {