[mutter] Fix identification of CSD windows when checking whether to force fullscreen

[Owen Taylor <otaylor src gnome org>]

commit 47273eaab69fa967cb575609f476a3cc53e6c3cd
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Wed Mar 5 19:01:11 2014 -0500

    Fix identification of CSD windows when checking whether to force fullscreen
    
    We try to exempt CSD windows from being forced fullscreen if they are
    undecorated and the size of the screen; however, we also catch almost
    all windows that *do* need to be forced fullscreen in this check, since
    they also have decorations turned off.
    
    Identify actual CSD windows by checking whether _GTK_FRAME_EXTENTS is set -
    GTK+ will always set this on CSD windows even if they have no invisible
    borders or shadows at the current time.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=723029

 src/core/constraints.c    |    2 +-
 src/core/window-private.h |    2 ++
 src/core/window.c         |   18 ++++++++++++++++++
 3 files changed, 21 insertions(+), 1 deletions(-)
---
diff --git a/src/core/constraints.c b/src/core/constraints.c
index b59aa06..c6950ce 100644
--- a/src/core/constraints.c
+++ b/src/core/constraints.c
@@ -426,7 +426,7 @@ setup_constraint_info (ConstraintInfo      *info,
    */
   if (meta_prefs_get_force_fullscreen() &&
       !window->hide_titlebar_when_maximized &&
-      window->decorated &&
+      (window->decorated || !meta_window_is_client_decorated (window)) &&
       meta_rectangle_equal (new, &monitor_info->rect) &&
       window->has_fullscreen_func &&
       !window->fullscreen)
diff --git a/src/core/window-private.h b/src/core/window-private.h
index b282efe..03f6715 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -694,4 +694,6 @@ Window meta_window_get_toplevel_xwindow (MetaWindow *window);
 void meta_window_get_client_area_rect (const MetaWindow      *window,
                                        cairo_rectangle_int_t *rect);
 
+gboolean meta_window_is_client_decorated (MetaWindow *window);
+
 #endif
diff --git a/src/core/window.c b/src/core/window.c
index 2593f27..2ac5a10 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -10127,6 +10127,24 @@ meta_window_same_client (MetaWindow *window,
           (other_window->xwindow & ~resource_mask));
 }
 
+/**
+ * meta_window_is_client_decorated:
+ *
+ * Check if if the window has decorations drawn by the client.
+ * (window->decorated refers only to whether we should add decorations)
+ */
+gboolean
+meta_window_is_client_decorated (MetaWindow *window)
+{
+  /* Currently the implementation here is hackish -
+   * has_custom_frame_extents() is set if _GTK_FRAME_EXTENTS is set
+   * to any value even 0. GTK+ always sets _GTK_FRAME_EXTENTS for
+   * client-side-decorated window, even if the value is 0 because
+   * the window is maxized and has no invisible borders or shadows.
+   */
+  return window->has_custom_frame_extents;
+}
+
 void
 meta_window_refresh_resize_popup (MetaWindow *window)
 {