[gnome-shell] altTab: Don't return from _init() if there are no windows/apps

[Florian Müllner <fmuellner src gnome org>]

commit 84250bbf8860de5930baf946cdde1768d1a726fa
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Sun May 6 17:17:33 2018 +0200

    altTab: Don't return from _init() if there are no windows/apps
    
    If a new SwitcherPopup is created and there are no windows or apps to
    switch through found, instead of returning from _init(), still
    initialize the SwitcherPopup and let the check in SwitcherPopup.show()
    return false to terminate the popup.
    
    In both cases, with or without the return statements,
    WindowManager._startSwitcher() will call SwicherPopup.destroy(), which
    will try to disconnect signal handlers, destroy actors etc. Now if the
    constructor can't finish creating the popup, some of the functions
    called from _onDestroy() will fail and throw errors.
    
    One of those cases is when window-switcher is limited to the current
    workspace, and a WindowCyclerPopup is initiated on an empty workspace.
    Because this._highlight hasn't been created, _onDestroy() will fail when
    trying to destroy the actor of this._highlight.
    
    Also, the actor of this._switcherList will not get destroyed in case
    show() returns because this._items is empty. For example, this will
    happen when a new AppSwitcherPopup is initialized with at least 1
    running app, but 0 windows on the active workspace.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/168

 js/ui/altTab.js        | 9 ---------
 js/ui/switcherPopup.js | 5 +++++
 2 files changed, 5 insertions(+), 9 deletions(-)
---
diff --git a/js/ui/altTab.js b/js/ui/altTab.js
index 1e4cbc4534..06b8d79744 100644
--- a/js/ui/altTab.js
+++ b/js/ui/altTab.js
@@ -64,9 +64,6 @@ class AppSwitcherPopup extends SwitcherPopup.SwitcherPopup {
 
         let apps = Shell.AppSystem.get_default().get_running();
 
-        if (apps.length == 0)
-            return;
-
         this._switcherList = new AppSwitcher(apps, this);
         this._items = this._switcherList.icons;
     }
@@ -481,9 +478,6 @@ var CyclerPopup = GObject.registerClass({
 
         this._items = this._getWindows();
 
-        if (this._items.length == 0)
-            return;
-
         this._highlight = new CyclerHighlight();
         global.window_group.add_actor(this._highlight);
 
@@ -559,9 +553,6 @@ class WindowSwitcherPopup extends SwitcherPopup.SwitcherPopup {
 
         let windows = this._getWindowList();
 
-        if (windows.length == 0)
-            return;
-
         let mode = this._settings.get_enum('app-icon-mode');
         this._switcherList = new WindowSwitcher(windows, mode);
         this._items = this._switcherList.icons;
diff --git a/js/ui/switcherPopup.js b/js/ui/switcherPopup.js
index 945f4020a5..d1322106e3 100644
--- a/js/ui/switcherPopup.js
+++ b/js/ui/switcherPopup.js
@@ -330,6 +330,11 @@ var SwitcherPopup = GObject.registerClass({
             GLib.source_remove(this._initialDelayTimeoutId);
         if (this._noModsTimeoutId != 0)
             GLib.source_remove(this._noModsTimeoutId);
+
+        // Make sure the SwitcherList is always destroyed, it may not be
+        // a child of the actor at this point.
+        if (this._switcherList)
+            this._switcherList.destroy();
     }
 
     _select(num) {