[gnome-shell] switcherPopup: Use local variable for index in scrolling functions

[Florian Müllner <fmuellner src gnome org>]

commit 172d21cf506e5fb6f49d4bad344323e289365442
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Wed Apr 25 23:24:05 2018 +0200

    switcherPopup: Use local variable for index in scrolling functions
    
    Make sure the index that's being scrolled to doesn't change while the
    scrolling animation is running by using an argument instead of the
    this._highlighed class scope variable.
    
    This fixes wrongly shown arrows when selecting new elements faster than
    the scrolling animation takes for one index. The check run to disable
    the arrow might be checking against a newer index than the one at the
    start of the animation which results in the arrow not getting hidden
    even if no more scrolling is possible.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/167

 js/ui/switcherPopup.js | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
---
diff --git a/js/ui/switcherPopup.js b/js/ui/switcherPopup.js
index d026453ca3..16aa24c649 100644
--- a/js/ui/switcherPopup.js
+++ b/js/ui/switcherPopup.js
@@ -467,17 +467,17 @@ var SwitcherList = GObject.registerClass({
         let [result_, posX, posY_] = this.transform_stage_point(absItemX, 0);
         let [containerWidth] = this.get_transformed_size();
         if (posX + this._items[index].get_width() > containerWidth)
-            this._scrollToRight();
+            this._scrollToRight(index);
         else if (this._items[index].allocation.x1 - value < 0)
-            this._scrollToLeft();
+            this._scrollToLeft(index);
 
     }
 
-    _scrollToLeft() {
+    _scrollToLeft(index) {
         let adjustment = this._scrollView.hscroll.adjustment;
         let [value, lower_, upper, stepIncrement_, pageIncrement_, pageSize] = adjustment.get_values();
 
-        let item = this._items[this._highlighted];
+        let item = this._items[index];
 
         if (item.allocation.x1 < value)
             value = Math.min(0, item.allocation.x1);
@@ -489,18 +489,18 @@ var SwitcherList = GObject.registerClass({
             progress_mode: Clutter.AnimationMode.EASE_OUT_QUAD,
             duration: POPUP_SCROLL_TIME,
             onComplete: () => {
-                if (this._highlighted == 0)
+                if (index === 0)
                     this._scrollableLeft = false;
                 this.queue_relayout();
             },
         });
     }
 
-    _scrollToRight() {
+    _scrollToRight(index) {
         let adjustment = this._scrollView.hscroll.adjustment;
         let [value, lower_, upper, stepIncrement_, pageIncrement_, pageSize] = adjustment.get_values();
 
-        let item = this._items[this._highlighted];
+        let item = this._items[index];
 
         if (item.allocation.x1 < value)
             value = Math.max(0, item.allocation.x1);
@@ -512,7 +512,7 @@ var SwitcherList = GObject.registerClass({
             progress_mode: Clutter.AnimationMode.EASE_OUT_QUAD,
             duration: POPUP_SCROLL_TIME,
             onComplete: () => {
-                if (this._highlighted == this._items.length - 1)
+                if (index === this._items.length - 1)
                     this._scrollableRight = false;
                 this.queue_relayout();
             },