window: Add get_all_monitors

Add a method that returns the indices of the monitors a window
is on.

https://bugzilla.gnome.org/show_bug.cgi?id=646861

src/core/window.c

@@ -3647,6 +3647,42 @@ meta_window_is_fullscreen (MetaWindow *window)
   return window->fullscreen;
 }
 
+/**
+ * meta_window_get_all_monitors:
+ * @window: The #MetaWindow
+ * @length: (out caller-allocates): gint holding the length, may be %NULL to
+ *                                  ignore
+ *
+ * Returns: (array length=length) (element-type gint) (transfer container):
+ *           List of the monitor indices the window is on.
+ */
+gint *
+meta_window_get_all_monitors (MetaWindow *window, gsize *length)
+{
+  GArray *monitors;
+  MetaRectangle window_rect;
+  int i;
+
+  monitors = g_array_new (FALSE, FALSE, sizeof (int));
+  meta_window_get_outer_rect (window, &window_rect);
+
+  for (i = 0; i < window->screen->n_monitor_infos; i++)
+    {
+      MetaRectangle *monitor_rect = &window->screen->monitor_infos[i].rect;
+
+      if (meta_rectangle_overlap (&window_rect, monitor_rect))
+        g_array_append_val (monitors, i);
+    }
+
+  if (length)
+    *length = monitors->len;
+
+  i = -1;
+  g_array_append_val (monitors, i);
+
+  return (gint*) g_array_free (monitors, FALSE);
+}
+
 /**
  * meta_window_is_screen_sized:
  *

src/meta/window.h

@@ -146,6 +146,7 @@ gboolean          meta_window_is_monitor_sized (MetaWindow *window);
 gboolean          meta_window_is_on_primary_monitor (MetaWindow *window);
 gboolean          meta_window_requested_bypass_compositor (MetaWindow *window);
 gboolean          meta_window_requested_dont_bypass_compositor (MetaWindow *window);
+gint             *meta_window_get_all_monitors (MetaWindow *window, gsize *length);
 
 gboolean meta_window_is_mapped (MetaWindow  *window);
 gboolean meta_window_toplevel_is_mapped (MetaWindow  *window);