[gnome-shell] appDisplay: Use icon grid size as distance passed to SwipeTracker

[Marge Bot <marge-bot src gnome org>]

commit 851a1e30fad49ff997c863132de1d7b8bc7470db
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Sun Apr 10 00:48:39 2022 +0200

    appDisplay: Use icon grid size as distance passed to SwipeTracker
    
    The swipeTracker wants the distance between two pages passed to it in
    confirmSwipe(). In case of the app grid, the correct distance is not the
    size of the scrollView (which has the width of the whole screen), but
    instead the allocation size of the iconGrid (which is the actual size
    of a page in the grid).
    
    So pass the allocation size of the iconGrid to the swipeTracker, this
    makes sure the pages move perfectly in sync with the pointer when
    dragging using the mouse or touchscreen.
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2275>

 js/ui/appDisplay.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 62d0c9c1ce..dd75a09edd 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -523,7 +523,7 @@ var BaseAppView = GObject.registerClass({
         const progress = adjustment.value / adjustment.page_size;
         const points = Array.from({ length: this._grid.nPages }, (v, i) => i);
         const size = tracker.orientation === Clutter.Orientation.VERTICAL
-            ? this._scrollView.height : this._scrollView.width;
+            ? this._grid.allocation.get_height() : this._grid.allocation.get_width();
 
         tracker.confirmSwipe(size, points, progress, Math.round(progress));
     }