[gnome-shell/wip/carlosg/magnifier-improvements: 7/11] magnifier: Add support for animating "scroll" on focus changes

[Carlos Garnacho <carlosg src gnome org>]

commit c0ae3f1ca3af836011920ab277d1a9c65c0fdbbe
Author: Carlos Garnacho <carlosg gnome org>
Date:   Thu Feb 6 11:00:44 2020 +0100

    magnifier: Add support for animating "scroll" on focus changes
    
    This is nice in that it provides a hint of the relative position of
    the new focus area, as opposed to a sudden jump.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/984

 js/ui/magnifier.js | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index 850cb8a261..15df336215 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -1395,7 +1395,8 @@ var ZoomRegion = class ZoomRegion {
                                         yMagFactor: this._yMagFactor,
                                         xCenter: this._xCenter,
                                         yCenter: this._yCenter,
-                                        redoCursorTracking: false });
+                                        redoCursorTracking: false,
+                                        animate: false });
 
         if (params.xMagFactor <= 0)
             params.xMagFactor = this._xMagFactor;
@@ -1434,8 +1435,7 @@ var ZoomRegion = class ZoomRegion {
                                 height: this._viewPortHeight }, true);
         }
 
-        this._updateCloneGeometry();
-        this._updateMousePosition();
+        this._updateCloneGeometry(params.animate);
     }
 
     _isMouseOverRegion() {
@@ -1573,17 +1573,39 @@ var ZoomRegion = class ZoomRegion {
         this._magView.set_position(this._viewPortX, this._viewPortY);
     }
 
-    _updateCloneGeometry() {
+    _setTransitionEasingState(actor, enabled) {
+        if (enabled) {
+            actor.save_easing_state();
+            actor.set_easing_mode(Clutter.AnimationMode.EASE_OUT_QUAD);
+            actor.set_easing_delay(100);
+        } else {
+            actor.restore_easing_state();
+        }
+    }
+
+    _updateCloneGeometry(animate = false) {
         if (!this.isActive())
             return;
 
+        if (animate) {
+            this._setTransitionEasingState(this._uiGroupClone, true);
+            this._setTransitionEasingState(this._mouseActor, true);
+            this._setTransitionEasingState(this._crossHairsActor, true);
+        }
+
         this._uiGroupClone.set_scale(this._xMagFactor, this._yMagFactor);
         this._mouseActor.set_scale(this._xMagFactor, this._yMagFactor);
 
         let [x, y] = this._screenToViewPort(0, 0);
-        this._uiGroupClone.set_position(Math.round(x), Math.round(y));
 
+        this._uiGroupClone.set_position(Math.round(x), Math.round(y));
         this._updateMousePosition();
+
+        if (animate) {
+            this._setTransitionEasingState(this._uiGroupClone, false);
+            this._setTransitionEasingState(this._mouseActor, false);
+            this._setTransitionEasingState(this._crossHairsActor, false);
+        }
     }
 
     _updateMousePosition() {