On 05/06/2013 05:39 PM, Eric Anholt wrote:
Ever since fake front was introduced in
63b51b5cf17ddde09b72a2811296f37b9a4c5ad2, we were skipping the XSync() in
the non-fake-front path, so compositors like Firefox's GL canvas were
having to manually put it in outside of glXWaitX().
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=52930
Both patches are
Reviewed-by: Ian Romanick <ian.d.roman...@intel.com>
and
NOTE: This is a candidate for the stable branches.
It might be worth adding the bit about pixmaps from the second commit
message to this one as well. I was unsure how you'd hit this problem
until I read the second patch.
---
src/glx/dri2_glx.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/src/glx/dri2_glx.c b/src/glx/dri2_glx.c
index 7ce5775..3cdd249 100644
--- a/src/glx/dri2_glx.c
+++ b/src/glx/dri2_glx.c
@@ -639,10 +639,23 @@ dri2_wait_x(struct glx_context *gc)
struct dri2_drawable *priv = (struct dri2_drawable *)
GetGLXDRIDrawable(gc->currentDpy, gc->currentDrawable);
- if (priv == NULL || !priv->have_fake_front)
- return;
-
- dri2_copy_drawable(priv, DRI2BufferFakeFrontLeft, DRI2BufferFrontLeft);
+ if (priv != NULL && priv->have_fake_front) {
+ /* Ask the server to update our copy of the front buffer from the real
+ * front buffer. This will round-trip with the server, so we can skip
+ * the XSync().
+ */
+ dri2_copy_drawable(priv, DRI2BufferFakeFrontLeft, DRI2BufferFrontLeft);
+ } else {
+ /* From the GLX 1.4 spec, page 33:
+ *
+ * "X rendering calls made prior to glXWaitX are guaranteed to be
+ * executed before OpenGL rendering calls made after
+ * glXWaitX. While the same result can be achieved using XSync,
+ * glXWaitX does not require a round trip to the server, and may
+ * therefore be more efficient."
+ */
+ XSync(gc->currentDpy, False);
+ }
}
static void
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