Compress motion synchronized with the paint cycle

When we have pending motion events, instead of delivering them
directly, request the new FLUSH_EVENTS phase of the frame clock.
This allows us to compress repeated motion events sent to the
same window.

In the FLUSH_EVENTS phase, which occur at priority GDK_PRIORITY_EVENTS + 1,
we deliver any pending motion events then turn off event delivery
until the end of the next frame. Turning off event delivery means
that we'll reliably paint the compressed motion events even if more
have arrived.

Add a motion-compression test case which demonstrates behavior when
an application takes too long handle motion events. It is unusable
without this patch but behaves fine with the patch.

https://bugzilla.gnome.org/show_bug.cgi?id=685460

1 files changed, 3 insertions, 0 deletions

diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index fb561e6f74..babef6e7f6 100644
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -300,6 +300,9 @@ GList* _gdk_event_queue_insert_after (GdkDisplay *display,
 GList* _gdk_event_queue_insert_before(GdkDisplay *display,
                                       GdkEvent   *after_event,
                                       GdkEvent   *event);
+
+void    _gdk_event_queue_handle_motion_compression (GdkDisplay *display);
+
 void   _gdk_event_button_generate    (GdkDisplay *display,
                                       GdkEvent   *event);