[gnome-shell] Magnifier: don't listen for focus/tracker events if the magnifier is not active

[Giovanni Campagna <gcampagna src gnome org>]

commit 3a92aa751fb0517e48e7320159b71196428a7e97
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Thu Feb 13 16:25:24 2014 +0100

    Magnifier: don't listen for focus/tracker events if the magnifier is not active
    
    In addition to checking the current settings, check also if the
    zoom region is active before registering the event listener.
    This way, we avoid DBus traffic for events we're not interested in.
    
    Also, make FocusCaretTracker resilient to multiple register/deregister
    calls (which can now happen).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=724305

 js/ui/focusCaretTracker.js |   34 ++++++++++++++++++++++++++++------
 js/ui/magnifier.js         |   29 +++++++++++++++++++++++------
 2 files changed, 51 insertions(+), 12 deletions(-)
---
diff --git a/js/ui/focusCaretTracker.js b/js/ui/focusCaretTracker.js
index 5af8d37..beaf2de 100644
--- a/js/ui/focusCaretTracker.js
+++ b/js/ui/focusCaretTracker.js
@@ -34,7 +34,11 @@ const FocusCaretTracker = new Lang.Class({
     _init: function() {
         Atspi.init();
         Atspi.set_timeout(250, 250);
+
         this._atspiListener = Atspi.EventListener.new(Lang.bind(this, this._onChanged));
+
+        this._focusListenerRegistered = false;
+        this._caretListenerRegistered = false;
     },
 
     _onChanged: function(event) {
@@ -45,21 +49,39 @@ const FocusCaretTracker = new Lang.Class({
     },
 
     registerFocusListener: function() {
-        return this._atspiListener.register(STATECHANGED + ':focused') &&
-               this._atspiListener.register(STATECHANGED + ':selected');
+        if (this._focusListenerRegistered)
+            return;
+
+        // Ignore the return value, we get an exception if they fail
+        // And they should never fail
+        this._atspiListener.register(STATECHANGED + ':focused');
+        this._atspiListener.register(STATECHANGED + ':selected');
+        this._focusListenerRegistered = true;
     },
 
     registerCaretListener: function() {
-        return this._atspiListener.register(CARETMOVED);
+        if (this._caretListenerRegistered)
+            return;
+
+        this._atspiListener.register(CARETMOVED);
+        this._caretListenerRegistered = true;
     },
 
     deregisterFocusListener: function() {
-        return this._atspiListener.deregister(STATECHANGED + ':focused') &&
-               this._atspiListener.deregister(STATECHANGED + ':selected');
+        if (!this._focusListenerRegistered)
+            return;
+
+        this._atspiListener.deregister(STATECHANGED + ':focused');
+        this._atspiListener.deregister(STATECHANGED + ':selected');
+        this._focusListenerRegistered = false;
     },
 
     deregisterCaretListener: function() {
-        return this._atspiListener.deregister(CARETMOVED);
+        if (!this._caretListenerRegistered)
+            return;
+
+        this._atspiListener.deregister(CARETMOVED);
+        this._caretListenerRegistered = false;
     }
 });
 Signals.addSignalMethods(FocusCaretTracker.prototype);
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index b02b114..f64ac3b 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -766,6 +766,9 @@ const ZoomRegion = new Lang.Class({
         } else {
             this._destroyActors();
         }
+
+        this._syncCaretTracking();
+        this._syncFocusTracking();
     },
 
     /**
@@ -825,10 +828,7 @@ const ZoomRegion = new Lang.Class({
      */
     setFocusTrackingMode: function(mode) {
         this._focusTrackingMode = mode;
-        if (this._focusTrackingMode == GDesktopEnums.MagnifierFocusTrackingMode.NONE)
-            this._focusCaretTracker.deregisterFocusListener();
-        else
-            this._focusCaretTracker.registerFocusListener();
+        this._syncFocusTracking();
     },
 
     /**
@@ -837,10 +837,27 @@ const ZoomRegion = new Lang.Class({
      */
     setCaretTrackingMode: function(mode) {
         this._caretTrackingMode = mode;
-        if (this._caretTrackingMode == GDesktopEnums.MagnifierCaretTrackingMode.NONE)
-            this._focusCaretTracker.deregisterCaretListener();
+        this._syncCaretTracking();
+    },
+
+    _syncFocusTracking: function() {
+        let enabled = this._focusTrackingMode != GDesktopEnums.MagnifierFocusTrackingMode.NONE &&
+            this.isActive();
+
+        if (enabled)
+            this._focusCaretTracker.registerFocusListener();
         else
+            this._focusCaretTracker.deregisterFocusListener();
+    },
+
+    _syncCaretTracking: function() {
+        let enabled = this._caretTrackingMode != GDesktopEnums.MagnifierCaretTrackingMode.NONE &&
+            this.isActive();
+
+        if (enabled)
             this._focusCaretTracker.registerCaretListener();
+        else
+            this._focusCaretTracker.deregisterCaretListener();
     },
 
     /**