[gnome-shell/gbsneto/icon-allocation-transition] iconGrid: Animate icon positions

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 02d69e6b6954927ec23c77de7b7f9b4c7a41203e
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed Dec 4 16:34:34 2019 -0300

    iconGrid: Animate icon positions

 js/ui/iconGrid.js | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)
---
diff --git a/js/ui/iconGrid.js b/js/ui/iconGrid.js
index 6d6ff5cbe2..3276b14eed 100644
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -28,6 +28,8 @@ var AnimationDirection = {
 var APPICON_ANIMATION_OUT_SCALE = 3;
 var APPICON_ANIMATION_OUT_TIME = 250;
 
+const ICON_POSITION_DELAY = 25;
+
 var BaseIcon = GObject.registerClass(
 class BaseIcon extends St.Bin {
     _init(label, params) {
@@ -194,6 +196,23 @@ function zoomOutActorAtPos(actor, x, y) {
     });
 }
 
+function animateIconPosition(icon, box, flags, nChangedIcons) {
+    if (!icon.has_allocation() || icon.allocation.equal(box)) {
+        icon.allocate(box, flags);
+        return false;
+    }
+
+    icon.save_easing_state();
+    icon.set_easing_mode(Clutter.AnimationMode.EASE_OUT_QUAD);
+    icon.set_easing_delay(nChangedIcons * ICON_POSITION_DELAY);
+
+    icon.allocate(box, flags);
+
+    icon.restore_easing_state();
+
+    return true;
+}
+
 var IconGrid = GObject.registerClass({
     Signals: { 'animation-done': {},
                'child-focused': { param_types: [Clutter.Actor.$gtype] } },
@@ -366,6 +385,7 @@ var IconGrid = GObject.registerClass({
         let y = box.y1 + this.topPadding;
         let columnIndex = 0;
         let rowIndex = 0;
+        let nChangedIcons = 0;
         for (let i = 0; i < children.length; i++) {
             let childBox = this._calculateChildBox(children[i], x, y, box);
 
@@ -375,7 +395,9 @@ var IconGrid = GObject.registerClass({
             } else {
                 if (!animating)
                     children[i].opacity = 255;
-                children[i].allocate(childBox, flags);
+
+                if (animateIconPosition(children[i], childBox, flags, nChangedIcons))
+                    nChangedIcons++;
             }
 
             columnIndex++;
@@ -875,9 +897,13 @@ var PaginatedIconGrid = GObject.registerClass({
         let y = box.y1 + this.topPadding;
         let columnIndex = 0;
 
+        let nChangedIcons = 0;
         for (let i = 0; i < children.length; i++) {
             let childBox = this._calculateChildBox(children[i], x, y, box);
-            children[i].allocate(childBox, flags);
+
+            if (animateIconPosition(children[i], childBox, flags, nChangedIcons))
+                nChangedIcons++;
+
             children[i].show();
 
             columnIndex++;