[effects/squash] Try to reverse previous active animations

Summary:
If a window is unminimized and the minimize animation is still active,
don't cancel the latter and start a new animation. Instead, try to
reverse already active animation and if that attempt failed, start a new
animation. This results in more smoother animations.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D16451

effects/squash/package/contents/code/main.js

@@ -37,11 +37,20 @@ var squashEffect = {
         }
 
         if (window.unminimizeAnimation) {
-            // TODO: Try to reverse it instead.
+            if (redirect(window.unminimizeAnimation, Effect.Backward)) {
+                return;
+            }
             cancel(window.unminimizeAnimation);
             delete window.unminimizeAnimation;
         }
 
+        if (window.minimizeAnimation) {
+            if (redirect(window.minimizeAnimation, Effect.Forward)) {
+                return;
+            }
+            cancel(window.minimizeAnimation);
+        }
+
         var windowRect = window.geometry;
 
         window.minimizeAnimation = animate({
@@ -94,11 +103,20 @@ var squashEffect = {
         }
 
         if (window.minimizeAnimation) {
-            // TODO: Try to reverse it instead.
+            if (redirect(window.minimizeAnimation, Effect.Backward)) {
+                return;
+            }
             cancel(window.minimizeAnimation);
             delete window.minimizeAnimation;
         }
 
+        if (window.unminimizeAnimation) {
+            if (redirect(window.unminimizeAnimation, Effect.Forward)) {
+                return;
+            }
+            cancel(window.unminimizeAnimation);
+        }
+
         var windowRect = window.geometry;
 
         window.unminimizeAnimation = animate({