[gnome-shell] magnifier: Disable desaturation effect when not in use

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

commit 34b6cd0beae9b712fb3f0402d83a45d99198b729
Author: Sebastian Keller <skeller gnome org>
Date:   Mon Nov 8 05:19:32 2021 +0100

    magnifier: Disable desaturation effect when not in use
    
    The desaturation effect was always enabled, regardless of the specified
    factor. This was causing the magnifier to always hit offscreen
    rendering, even when not necessary. Additionally offscreen rendering is
    currently also causing glitches in MetaWindowGroup which this helps to
    avoid in some cases.
    
    Related: https://gitlab.gnome.org/GNOME/mutter/-/issues/1678
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2026>

 js/ui/magnifier.js | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index 180df25460..2443248d34 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -1898,6 +1898,7 @@ var MagShaderEffects = class MagShaderEffects {
         this._colorDesaturation = new Clutter.DesaturateEffect();
         this._inverse.set_enabled(false);
         this._brightnessContrast.set_enabled(false);
+        this._colorDesaturation.set_enabled(false);
 
         this._magView = uiGroupClone;
         this._magView.add_effect(this._inverse);
@@ -1930,6 +1931,7 @@ var MagShaderEffects = class MagShaderEffects {
 
     setColorSaturation(factor) {
         this._colorDesaturation.set_factor(1.0 - factor);
+        this._colorDesaturation.set_enabled(factor !== 1.0);
     }
 
     /**