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

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 41dd72bc5dd08d7d0cb136f694a6d9a30e38b341
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 |    1 +
 src/core/window.c         |   18 ++++++++++++++++++
 3 files changed, 20 insertions(+), 1 deletions(-)
---
diff --git a/src/core/constraints.c b/src/core/constraints.c
index 0dc93cb..a937f05 100644
--- a/src/core/constraints.c
+++ b/src/core/constraints.c
@@ -438,7 +438,7 @@ setup_constraint_info (ConstraintInfo      *info,
    * workarea smaller than the monitor.
    */
   if (meta_prefs_get_force_fullscreen() &&
-      window->decorated &&
+      (window->decorated || !meta_window_is_client_decorated (window)) &&
       meta_rectangle_equal (new, &xinerama_info->rect) &&
       window->has_fullscreen_func &&
       !window->fullscreen)
diff --git a/src/core/window-private.h b/src/core/window-private.h
index a98cee3..2eb8ae6 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -660,5 +660,6 @@ void meta_window_unset_demands_attention (MetaWindow *window);
 void meta_window_update_icon_now (MetaWindow *window);
 
 gboolean meta_window_can_tile_side_by_side (MetaWindow *window);
+gboolean meta_window_is_client_decorated (MetaWindow *window);
 
 #endif
diff --git a/src/core/window.c b/src/core/window.c
index 74994bd..8e4345d 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -8474,3 +8474,21 @@ meta_window_is_maximized (MetaWindow *window)
 {
   return META_WINDOW_MAXIMIZED (window);
 }
+
+/**
+ * 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;
+}