[gnome-shell/gnome-3-36] iconGrid: Account for display scaling when scaling down icons

[Florian Müllner <fmuellner src gnome org>]

commit 4718f46618ab9da806895f7862d79968214c767f
Author: Sebastian Keller <skeller gnome org>
Date:   Fri Aug 21 17:08:45 2020 +0200

    iconGrid: Account for display scaling when scaling down icons
    
    Using display scaling (without 'scale-monitor-framebuffer') means the
    CSS item size the (fixed)ItemSize is calculated from has been multiplied
    by the scaling factor. So when subtracting the hardcoded icon size from
    this to calculate the size of the non-icon content of the item, it needs
    to be multiplied by the scaling factor as well.
    
    Then once the new icon size has been calculated after accounting for the
    non-icon content, the resulting size has to be divided by the scaling
    factor, because StIcon expects the unscaled icon size. Otherwise the
    icon would get scaled twice.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3090
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1420

 js/ui/iconGrid.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/iconGrid.js b/js/ui/iconGrid.js
index 6e691c58ad..1269a5432e 100644
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -845,10 +845,11 @@ var IconGrid = GObject.registerClass({
     // Note that this is ICON_SIZE as used by BaseIcon, not elsewhere in IconGrid; it's a bit messed up
     _updateIconSizes() {
         this._updateIconSizesLaterId = 0;
-        let extraWidth = Math.max(0, this._hItemSize - ICON_SIZE);
-        let extraHeight = Math.max(0, this._vItemSize - ICON_SIZE);
+        let scaleFactor = St.ThemeContext.get_for_stage(global.stage).scale_factor;
+        let extraWidth = Math.max(0, this._hItemSize - scaleFactor * ICON_SIZE);
+        let extraHeight = Math.max(0, this._vItemSize - scaleFactor * ICON_SIZE);
         let newIconSize = Math.min(this._fixedHItemSize - extraWidth,
-                                   this._fixedVItemSize - extraHeight);
+                                   this._fixedVItemSize - extraHeight) / scaleFactor;
         for (let i in this._items)
             this._items[i].icon.setIconSize(newIconSize);