From kde-commits  Tue Jan 06 06:55:04 2015
From: =?utf-8?q?Fredrik_H=C3=B6glund?= <fredrik () kde ! org>
Date: Tue, 06 Jan 2015 06:55:04 +0000
To: kde-commits
Subject: [kwin] /: Use swap events to drive repaints
Message-Id: <E1Y8O2i-0001ky-Bk () scm ! kde ! org>
X-MARC-Message: https://marc.info/?l=kde-commits&m=142052731322500

Git commit 38f1945c6c437cad14e9c22929ab7947009de8e5 by Fredrik H=C3=B6glund.
Committed on 13/12/2014 at 13:26.
Pushed by fredrik into branch 'master'.

Use swap events to drive repaints

Don't start the composite timer at the end of performPaint() when a
buffer swap is pending and vsync is enabled.  Instead set
m_composeAtSwapCompletion to true so performPaint() gets called again
as soon as the swap completes.

This makes the repaint cycle look like this:

    scene->paint()
    SwapBuffers()
    Process events
          =C2=B7
          =C2=B7
    Swap completes
    Fetch and reset damage (if applicable)
    scene->paint()
    SwapBuffers()
    Process events
          =C2=B7
          =C2=B7
    Swap completes
    ...

This results in a noticeable improvement in animation smoothness with
drivers that support GLX_INTEL_swap_event, since we're now able to
consistently render at the monitor refresh rate.

M  +5    -1    composite.cpp

http://commits.kde.org/kwin/38f1945c6c437cad14e9c22929ab7947009de8e5

diff --git a/composite.cpp b/composite.cpp
index c4145a3..1ded8e9 100644
--- a/composite.cpp
+++ b/composite.cpp
@@ -663,7 +663,11 @@ void Compositor::performCompositing()
     // is called the next time. If there would be nothing pending, it will=
 not restart the timer and
     // scheduleRepaint() would restart it again somewhen later, called fro=
m functions that
     // would again add something pending.
-    scheduleRepaint();
+    if (m_bufferSwapPending && m_scene->syncsToVBlank()) {
+        m_composeAtSwapCompletion =3D true;
+    } else {
+        scheduleRepaint();
+    }
 }
 =

 bool Compositor::windowRepaintsPending() const