Allow overshoot in the multitasking view

lib/Gestures/GestureController.vala

@@ -61,8 +61,8 @@ public class Gala.GestureController : Object {
     public double progress {
         get { return _progress; }
         set {
-            _progress = value;
-            target?.propagate (UPDATE, action, value);
+            _progress = value.clamp (overshoot_lower_clamp, overshoot_upper_clamp);
+            target?.propagate (UPDATE, action, _progress);
         }
     }
 

lib/Gestures/Targets/PropertyTarget.vala

@@ -6,6 +6,26 @@
  */
 
 public class Gala.PropertyTarget : Object, GestureTarget {
+    static construct {
+        /* The default progress func starts from the beginning when it overflows but we want
+           to clamp. E.g. when the multitasking view overshoots we want the opacity
+           to stay at max and not switch to 0 again. */
+        Clutter.Interval.register_progress_func (typeof (uint8), uint8_progress_func);
+    }
+
+    private static bool uint8_progress_func (Value a, Value b, double progress, Value result) {
+        if (a.type () != typeof (uint8) || b.type () != typeof (uint8)) {
+            return false;
+        }
+
+        var a_val = a.get_uchar ();
+        var b_val = b.get_uchar ();
+
+        var res = (uint8) (a_val + progress * b_val).clamp (0, 255);
+        result.set_uchar (res);
+        return true;
+    }
+
     public GestureAction action { get; construct; }
     // Don't take a reference since we are most of the time owned by the target
     public weak Object? target { get; private set; }

src/ShellClients/ExtendedBehaviorWindow.vala

@@ -10,7 +10,7 @@ public class Gala.ExtendedBehaviorWindow : ShellWindow {
     public bool dim { get; private set; default = false; }
 
     public ExtendedBehaviorWindow (Meta.Window window) {
-        var target = new PropertyTarget (CUSTOM, window.get_compositor_private (), "opacity", typeof (uint), 255u, 0u);
+        var target = new PropertyTarget (CUSTOM, window.get_compositor_private (), "opacity", typeof (uint8), (uint8) 255u, (uint8) 0u);
         Object (window: window, hide_target: target);
     }
 

src/Widgets/MultitaskingView/MultitaskingView.vala

@@ -59,7 +59,10 @@ public class Gala.MultitaskingView : ActorTarget, RootTarget, ActivatableCompone
         opened = false;
         display = wm.get_display ();
 
-        multitasking_gesture_controller = new GestureController (MULTITASKING_VIEW);
+        multitasking_gesture_controller = new GestureController (MULTITASKING_VIEW) {
+            overshoot_upper_clamp = 1.1,
+            overshoot_lower_clamp = -0.1,
+        };
         multitasking_gesture_controller.add_trigger (new GlobalTrigger (MULTITASKING_VIEW, wm));
         add_gesture_controller (multitasking_gesture_controller);
 

src/Widgets/MultitaskingView/StaticWindowClone.vala

@@ -22,7 +22,7 @@ public class Gala.StaticWindowClone : ActorTarget {
         var clone = new Clutter.Clone (window_actor);
         add_child (clone);
 
-        add_target (new PropertyTarget (MULTITASKING_VIEW, this, "opacity", typeof (uint), 255u, 0u));
+        add_target (new PropertyTarget (MULTITASKING_VIEW, this, "opacity", typeof (uint8), (uint8) 255u, (uint8) 0u));
 
         window_actor.bind_property ("x", this, "x", SYNC_CREATE);
         window_actor.bind_property ("y", this, "y", SYNC_CREATE);

src/Widgets/MultitaskingView/WindowClone.vala

@@ -274,11 +274,11 @@ public class Gala.WindowClone : ActorTarget, RootTarget {
             opacity = 255u;
         }
 
-        add_target (new PropertyTarget (MULTITASKING_VIEW, window_icon, "opacity", typeof (uint), 0u, 255u));
+        add_target (new PropertyTarget (MULTITASKING_VIEW, window_icon, "opacity", typeof (uint8), (uint8) 0u, (uint8) 255u));
 
-        add_target (new PropertyTarget (MULTITASKING_VIEW, window_title, "opacity", typeof (uint), 0u, 255u));
+        add_target (new PropertyTarget (MULTITASKING_VIEW, window_title, "opacity", typeof (uint8), (uint8) 0u, (uint8) 255u));
 
-        add_target (new PropertyTarget (MULTITASKING_VIEW, close_button, "opacity", typeof (uint), 0u, 255u));
+        add_target (new PropertyTarget (MULTITASKING_VIEW, close_button, "opacity", typeof (uint8), (uint8) 0u, (uint8) 255u));
     }
 
     public override void update_progress (Gala.GestureAction action, double progress) {