messageTray: Don't use focus grabs

We can easily implement much of the same behavior ourselves by
keeping track of Clutter's focus events. Reintroduce heavily
modified FocusGrabber to do the work for us.

This will temporarily break when the user selects a window until
we can make gnome-shell automatically set the stage focus.

This also removes our only use of focus grabs, so remove those
as well.

https://bugzilla.gnome.org/show_bug.cgi?id=700735

js/ui/messageTray.js

@@ -97,6 +97,65 @@ function _fixMarkup(text, allowMarkup) {
     return GLib.markup_escape_text(text, -1);
 }
 
+const FocusGrabber = new Lang.Class({
+    Name: 'FocusGrabber',
+
+    _init: function(actor) {
+        this._actor = actor;
+        this._prevKeyFocusActor = null;
+        this._focusActorChangedId = 0;
+        this._focused = false;
+    },
+
+    grabFocus: function() {
+        if (this._focused)
+            return;
+
+        this._prevFocusedWindow = global.display.focus_window;
+        this._prevKeyFocusActor = global.stage.get_key_focus();
+
+        this._focusActorChangedId = global.stage.connect('notify::key-focus', Lang.bind(this, this._focusActorChanged));
+
+        if (!this._actor.navigate_focus(null, Gtk.DirectionType.TAB_FORWARD, false))
+            this._actor.grab_key_focus();
+
+        this._focused = true;
+    },
+
+    _focusUngrabbed: function() {
+        if (!this._focused)
+            return false;
+
+        if (this._focusActorChangedId > 0) {
+            global.stage.disconnect(this._focusActorChangedId);
+            this._focusActorChangedId = 0;
+        }
+
+        this._focused = false;
+        return true;
+    },
+
+    _focusActorChanged: function() {
+        let focusedActor = global.stage.get_key_focus();
+        if (!focusedActor || !this._actor.contains(focusedActor))
+            this._focusUngrabbed();
+    },
+
+    ungrabFocus: function() {
+        if (!this._focusUngrabbed())
+            return;
+
+        if (this._prevKeyFocusActor) {
+            global.stage.set_key_focus(this._prevKeyFocusActor);
+            this._prevKeyFocusActor = null;
+        } else {
+            let focusedActor = global.stage.get_key_focus();
+            if (focusedActor && this._actor.contains(focusedActor))
+                global.stage.set_key_focus(null);
+        }
+    }
+});
+
 const URLHighlighter = new Lang.Class({
     Name: 'URLHighlighter',
 
@@ -1574,6 +1633,7 @@ const MessageTray = new Lang.Class({
         this._notificationBin.set_y_align(Clutter.ActorAlign.START);
         this._notificationWidget.add_actor(this._notificationBin);
         this._notificationWidget.hide();
+        this._notificationFocusGrabber = new FocusGrabber(this._notificationWidget);
         this._notificationQueue = [];
         this._notification = null;
         this._notificationClickedId = 0;
@@ -1623,7 +1683,6 @@ const MessageTray = new Lang.Class({
                                                      { keybindingMode: Shell.KeyBindingMode.MESSAGE_TRAY });
         this._grabHelper.addActor(this._summaryBoxPointer.actor);
         this._grabHelper.addActor(this.actor);
-        this._grabHelper.addActor(this._notificationWidget);
 
         Main.layoutManager.connect('keyboard-visible-changed', Lang.bind(this, this._onKeyboardVisibleChanged));
 
@@ -2520,19 +2579,7 @@ const MessageTray = new Lang.Class({
     },
 
     _hideNotification: function() {
-        // HACK!
-        // There seems to be a reentrancy issue in calling .ungrab() here,
-        // which causes _updateState to be called before _notificationState
-        // becomes HIDING. That hides the notification again, nullifying the
-        // object but not setting _notificationState (and that's the weird part)
-        // As then _notificationState is stuck into SHOWN but _notification
-        // is null, every new _updateState fails and the message tray is
-        // lost forever.
-        //
-        // See more at https://bugzilla.gnome.org/show_bug.cgi?id=683986
-        this._notificationState = State.HIDING;
-
-        this._grabHelper.ungrab({ actor: this._notification.actor });
+        this._notificationFocusGrabber.ungrabFocus();
 
         if (this._notificationExpandedId) {
             this._notification.disconnect(this._notificationExpandedId);
@@ -2630,8 +2677,7 @@ const MessageTray = new Lang.Class({
     },
 
     _ensureNotificationFocused: function() {
-        this._grabHelper.grab({ actor: this._notification.actor,
-                                grabFocus: true });
+        this._notificationFocusGrabber.grabFocus();
     },
 
     _onSourceDoneDisplayingContent: function(source, closeTray) {