window: Parse _GTK_THEME_VARIANT property

Since version 3.0, GTK+ has support for style variants. At the moment,
themes may provide a dark variant, which can be requested by
applications via GtkSettings. The requested variant is exported to
X11 via the _GTK_THEME_VARIANT property - support this property, in
order to pick up the correct style variant in the future.

https://bugzilla.gnome.org/show_bug.cgi?id=645355

NOTE: Patch is adapted for marco.

upstream commit:
https://gitlab.gnome.org/GNOME/metacity/commit/341d0945

4 files changed, 27 insertions, 0 deletions

diff --git a/src/core/atomnames.h b/src/core/atomnames.h
index 8e149060..3744f428 100644
--- a/src/core/atomnames.h
+++ b/src/core/atomnames.h
@@ -58,6 +58,7 @@ item(_MARCO_RESTART_MESSAGE)
 item(_MARCO_RELOAD_THEME_MESSAGE)
 item(_MARCO_SET_KEYBINDINGS_MESSAGE)
 item(_MARCO_TOGGLE_VERBOSE)
+item(_GTK_THEME_VARIANT)
 item(_GTK_FRAME_EXTENTS)
 item(_GTK_SHOW_WINDOW_MENU)
 item(_MATE_PANEL_ACTION)
diff --git a/src/core/window-private.h b/src/core/window-private.h
index a6b6418c..38184231 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -117,6 +117,7 @@ struct _MetaWindow
   char *sm_client_id;
   char *wm_client_machine;
   char *startup_id;
+  char *gtk_theme_variant;
 
   int net_wm_pid;
 
diff --git a/src/core/window-props.c b/src/core/window-props.c
index c3200290..0f492a5e 100644
--- a/src/core/window-props.c
+++ b/src/core/window-props.c
@@ -1530,6 +1530,28 @@ reload_transient_for (MetaWindow    *window,
     meta_window_queue (window, META_QUEUE_MOVE_RESIZE);
 }
 
+static void
+reload_gtk_theme_variant (MetaWindow    *window,
+                          MetaPropValue *value,
+                          gboolean       initial)
+{
+  char *requested_variant = NULL;
+  char *current_variant = window->gtk_theme_variant;
+
+  if (value->type != META_PROP_VALUE_INVALID)
+    {
+      requested_variant = value->v.str;
+      meta_verbose ("Requested \"%s\" theme variant for window %s.\n",
+                    requested_variant, window->desc);
+    }
+
+  if (g_strcmp0 (requested_variant, current_variant) != 0)
+    {
+      g_free (current_variant);
+
+      window->gtk_theme_variant = g_strdup (requested_variant);
+    }
+}
 /**
  * Initialises the property hooks system.  Each row in the table named "hooks"
  * represents an action to take when a property is found on a newly-created
@@ -1576,6 +1598,7 @@ meta_display_init_window_prop_hooks (MetaDisplay *display)
     { XA_WM_HINTS,                     META_PROP_VALUE_WM_HINTS,  reload_wm_hints },
     { XA_WM_TRANSIENT_FOR,             META_PROP_VALUE_WINDOW,    reload_transient_for },
     { display->atom__NET_WM_USER_TIME_WINDOW, META_PROP_VALUE_WINDOW, reload_net_wm_user_time_window },
+    { display->atom__GTK_THEME_VARIANT, META_PROP_VALUE_UTF8, reload_gtk_theme_variant, },
     { display->atom__GTK_FRAME_EXTENTS, META_PROP_VALUE_CARDINAL_LIST, reload_gtk_frame_extents },
     { 0 },
   };
diff --git a/src/core/window.c b/src/core/window.c
index bba84b4c..ba50fc51 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -561,6 +561,7 @@ meta_window_new_with_attrs (MetaDisplay       *display,
   window->sm_client_id = NULL;
   window->wm_client_machine = NULL;
   window->startup_id = NULL;
+  window->gtk_theme_variant = NULL;
 
   window->net_wm_pid = -1;
 
@@ -1229,6 +1230,7 @@ meta_window_free (MetaWindow  *window,
   g_free (window->title);
   g_free (window->icon_name);
   g_free (window->desc);
+  g_free (window->gtk_theme_variant);
   g_free (window);
 }