[mutter] meta-window-actor: Fix offset calculation in queue_send_frame_messages_timeout

[Adel Gadllah <agadllah src gnome org>]

commit 36be0846552d08fd093dda01a6860cb92387f1b9
Author: Adel Gadllah <adel gadllah gmail com>
Date:   Mon Oct 7 17:51:12 2013 +0200

    meta-window-actor: Fix offset calculation in queue_send_frame_messages_timeout
    
    The current time offset calculation is wrong. It is supposed to calculate
    the offset between the current time and the
    "time where it message should be sent" (last_time + interval).
    
    Fix the math to actually do that.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=709340

 src/compositor/meta-window-actor.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index 7dc8bf0..77a0f25 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -973,7 +973,7 @@ queue_send_frame_messages_timeout (MetaWindowActor *self)
     }
 
   interval = (int)(1000000 / refresh_rate) * 6;
-  offset = MAX (0, current_time - priv->frame_drawn_time + interval) / 1000;
+  offset = MAX (0, priv->frame_drawn_time + interval - current_time) / 1000;
 
  /* The clutter master clock source has already been added with META_PRIORITY_REDRAW,
   * so the timer will run *after* the clutter frame handling, if a frame is ready