workspace: Don't try to use per-workspace MRU lists as a hint for focusing

Commit 2fc880db switched from focusing the topmost window as the default
window to focusing the MRU window. This was done in alignment with the
introduction of per-workspace MRU lists to avoid problems where the window
stack was inadvertently changed when focusing windows during window switches.

Now that focusing windows don't have as big an impact on the stacking order,
we can revert back to focusing the top window, which is less confusing to the
user.

For now, leave per-workspace MRU lists, as they're a pretty good approximation
of a global MRU list, and it works well enough.

https://bugzilla.gnome.org/show_bug.cgi?id=620744

doc/how-to-get-focus-right.txt

@@ -31,8 +31,7 @@ workspaces.  In these cases, there needs to be a rule consistent with
 the above about the new window to choose.
 
 Focus method  Behavior
-    click     Focus the most recently used window (same as the window
+    click     Focus the window on top
-              on top)
    sloppy     Focus the window containing the pointer if there is such
               a window, otherwise focus the most recently used window.
     mouse     Focus the non-DESKTOP window containing the pointer if

src/core/workspace-private.h

@@ -42,6 +42,16 @@ struct _MetaWorkspace
   MetaScreen *screen;
   
   GList *windows;
+
+  /* The "MRU list", or "most recently used" list, is a list of
+   * MetaWindows ordered based on the time the the user interacted
+   * with the window most recently.
+   *
+   * For historical reasons, we keep an MRU list per workspace.
+   * It used to be used to calculate the default focused window,
+   * but isn't anymore, as the window next in the stacking order
+   * can sometimes be not the window the user interacted with last,
+   */
   GList *mru_list;
 
   GList  *list_containing_self;

src/core/workspace.c

@@ -46,7 +46,7 @@ enum {
 };
 
 void meta_workspace_queue_calc_showing   (MetaWorkspace *workspace);
-static void focus_ancestor_or_mru_window (MetaWorkspace *workspace,
+static void focus_ancestor_or_top_window (MetaWorkspace *workspace,
                                           MetaWindow    *not_this_one,
                                           guint32        timestamp);
 static void free_this                    (gpointer candidate,
@@ -1201,7 +1201,7 @@ meta_workspace_focus_default_window (MetaWorkspace *workspace,
 
   if (meta_prefs_get_focus_mode () == G_DESKTOP_FOCUS_MODE_CLICK ||
       !workspace->screen->display->mouse_mode)
-    focus_ancestor_or_mru_window (workspace, not_this_one, timestamp);
+    focus_ancestor_or_top_window (workspace, not_this_one, timestamp);
   else
     {
       MetaWindow * window;
@@ -1238,7 +1238,7 @@ meta_workspace_focus_default_window (MetaWorkspace *workspace,
             }
         }
       else if (meta_prefs_get_focus_mode () == G_DESKTOP_FOCUS_MODE_SLOPPY)
-        focus_ancestor_or_mru_window (workspace, not_this_one, timestamp);
+        focus_ancestor_or_top_window (workspace, not_this_one, timestamp);
       else if (meta_prefs_get_focus_mode () == G_DESKTOP_FOCUS_MODE_MOUSE)
         {
           meta_topic (META_DEBUG_FOCUS,
@@ -1261,17 +1261,13 @@ record_ancestor (MetaWindow *window,
   return FALSE; /* quit with the first ancestor we find */
 }
 
-/* Focus ancestor of not_this_one if there is one, otherwise focus the MRU
+/* Focus ancestor of not_this_one if there is one */
- * window on active workspace
- */
 static void
-focus_ancestor_or_mru_window (MetaWorkspace *workspace,
+focus_ancestor_or_top_window (MetaWorkspace *workspace,
                               MetaWindow    *not_this_one,
                               guint32        timestamp)
 {
   MetaWindow *window = NULL;
-  MetaWindow *desktop_window = NULL;
-  GList *tmp;
 
   if (not_this_one)
     meta_topic (META_DEBUG_FOCUS,
@@ -1305,36 +1301,9 @@ focus_ancestor_or_mru_window (MetaWorkspace *workspace,
         }
     }
 
-  /* No ancestor, look for the MRU window */
+  window = meta_stack_get_default_focus_window (workspace->screen->stack,
-  tmp = workspace->mru_list;  
+                                                workspace,
-
+                                                NULL);
-  while (tmp)
-    {
-      MetaWindow* tmp_window;
-      tmp_window = ((MetaWindow*) tmp->data);
-      if (tmp_window != not_this_one           &&
-          meta_window_showing_on_its_workspace (tmp_window) &&
-          tmp_window->type != META_WINDOW_DOCK &&
-          tmp_window->type != META_WINDOW_DESKTOP)
-        {
-          window = tmp->data;
-          break;
-        }
-      else if (tmp_window != not_this_one      &&
-               desktop_window == NULL          &&
-               meta_window_showing_on_its_workspace (tmp_window) &&
-               tmp_window->type == META_WINDOW_DESKTOP)
-        {
-          /* Found the most recently used desktop window */
-          desktop_window = tmp_window;
-        }
-
-      tmp = tmp->next;
-    }
-
-  /* If no window was found, default to the MRU desktop-window */
-  if (window == NULL)
-    window = desktop_window;
 
   if (window)
     {