[gnome-shell] magnifier: Track cursor sprite changes only when active

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

commit 9158f55360d6af87c078d3af3db81f296f3b36b3
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Mon Mar 11 17:09:08 2019 -0400

    magnifier: Track cursor sprite changes only when active
    
    There's no point in keeping the cursor sprite texture around all the time,
    and to listen for its changes, we just need this when the magnifier is active.
    
    So, initialize the magnifier texture and monitor for the sprite changes on
    activation, while disconnect from the signal and nullify the texture when
    the magnifier is deactivated.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/443

 js/ui/magnifier.js | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index f6b0e9550..b01e8b6b2 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -88,7 +88,7 @@ var MouseSpriteContent = GObject.registerClass({
         this._texture = coglTexture;
         this.invalidate();
 
-        if (!oldTexture ||
+        if (!oldTexture || !coglTexture ||
             oldTexture.get_width() != coglTexture.get_width() ||
             oldTexture.get_height() != coglTexture.get_height())
             this.invalidate_size();
@@ -106,7 +106,6 @@ var Magnifier = class Magnifier {
 
         this._mouseSprite = new Clutter.Actor({ request_mode: Clutter.RequestMode.CONTENT_SIZE });
         this._mouseSprite.content = new MouseSpriteContent();
-        this._updateSpriteTexture();
 
         this._cursorRoot = new Clutter.Actor();
         this._cursorRoot.add_actor(this._mouseSprite);
@@ -122,8 +121,6 @@ var Magnifier = class Magnifier {
         let showAtLaunch = this._settingsInit(aZoomRegion);
         aZoomRegion.scrollContentsTo(this.xMouse, this.yMouse);
 
-        cursorTracker.connect('cursor-changed', this._updateMouseSprite.bind(this));
-
         // Export to dbus.
         magDBusService = new MagnifierDBus.ShellMagnifier();
         this.setActive(showAtLaunch);
@@ -159,9 +156,15 @@ var Magnifier = class Magnifier {
 
         if (isActive != activate) {
             if (activate) {
+                this._updateMouseSprite();
+                this._cursorSpriteChangedId =
+                    this._cursorTracker.connect('cursor-changed',
+                                                this._updateMouseSprite.bind(this));
                 Meta.disable_unredirect_for_display(global.display);
                 this.startTrackingMouse();
             } else {
+                this._cursorTracker.disconnect(this._cursorSpriteChangedId);
+                this._mouseSprite.content.texture = null;
                 Meta.enable_unredirect_for_display(global.display);
                 this.stopTrackingMouse();
             }