[gnome-shell/wip/carlosg/magnifier-fixes: 2/3] magnifier: Add method to enable/disable crosshairs

[Carlos Garnacho <carlosg src gnome org>]

commit b5b8d08ed781b7b863d7943a5ef253cd2020594f
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Jun 28 14:19:15 2021 +0200

    magnifier: Add method to enable/disable crosshairs
    
    These do some some signals connection and monitor layout tracking
    that we forget to disconnect when the magnifier is disconnected.
    This causes warnings if enabling the magnifier, diabling it,
    switching to another tty, and back. (Presumably also happens for
    monitor hotplugs).
    
    This signal should just stay connected as long as it's needed,
    so add a setEnabled() method on the CrossHairs actor that we
    can hook on the magnifier.

 js/ui/magnifier.js | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index 22c11766b0..c8f695e2b6 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -172,6 +172,9 @@ var Magnifier = class Magnifier {
             this.stopTrackingMouse();
         }
 
+        if (this._crossHairs)
+            this._crossHairs.setEnabled(activate);
+
         // Make sure system mouse pointer is shown when all zoom regions are
         // invisible.
         if (!activate)
@@ -1677,9 +1680,7 @@ class Crosshairs extends Clutter.Actor {
         this._clipSize = [0, 0];
         this._clones = [];
         this.reCenter();
-
-        Main.layoutManager.connect('monitors-changed',
-                                   this._monitorsChanged.bind(this));
+        this._monitorsChangedId = 0;
     }
 
     _monitorsChanged() {
@@ -1687,6 +1688,16 @@ class Crosshairs extends Clutter.Actor {
         this.reCenter();
     }
 
+    setEnabled(enabled) {
+        if (enabled && this._monitorsChangedId === 0) {
+            this._monitorsChangedId = Main.layoutManager.connect(
+                'monitors-changed', this._monitorsChanged.bind(this));
+        } else if (!enabled && this._monitorsChangedId !== 0) {
+            Main.layoutManager.disconnect(this._monitorsChangedId);
+            this._monitorsChangedId = 0;
+        }
+    }
+
     /**
     * addToZoomRegion
     * Either add the crosshairs actor to the given ZoomRegion, or, if it is