cogl/onscreen: Add way to manually add frame infos

We will soon need to use CoglOnscreen frame events communicate cursor
plane changes; this means we need to have a way to queue them without
going through any of the current APIs that can do so, i.e. the swap
buffer functions and direct scanout.

Add a function that just adds a frame info to the queue. The one who
adds it is responsible for emitting it too.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>

cogl/cogl/cogl-onscreen.c

@@ -457,6 +457,14 @@ cogl_onscreen_direct_scanout (CoglOnscreen   *onscreen,
   return TRUE;
 }
 
+void
+cogl_onscreen_add_frame_info (CoglOnscreen  *onscreen,
+                              CoglFrameInfo *info)
+{
+  info->frame_counter = onscreen->frame_counter;
+  g_queue_push_tail (&onscreen->pending_frame_infos, info);
+}
+
 #ifdef COGL_HAS_X11_SUPPORT
 uint32_t
 cogl_x11_onscreen_get_window_xid (CoglOnscreen *onscreen)

cogl/cogl/cogl-onscreen.h

@@ -304,6 +304,13 @@ cogl_onscreen_direct_scanout (CoglOnscreen   *onscreen,
                               gpointer        user_data,
                               GError        **error);
 
+/**
+ * cogl_onscreen_add_frame_info: (skip)
+ */
+COGL_EXPORT void
+cogl_onscreen_add_frame_info (CoglOnscreen  *onscreen,
+                              CoglFrameInfo *info);
+
 /**
  * cogl_onscreen_swap_region:
  * @onscreen: A #CoglOnscreen framebuffer