glXSwapBuffersMscOML() with target_msc=divisor=remainder=0 gets
translated into target_msc=divisor=0 but remainder=1 by the mesa
api. This is done for server DRI2 where there needs to be a way
to tell the server-side DRI2ScheduleSwap implementation if a call
to glXSwapBuffers() or glXSwapBuffersMscOML(dpy,window,0,0,0) was
done. remainder = 1 was (ab)used as a flag to tell the server to
select proper semantic. The DRI3/Present backend ignored this
signalling, treated any target_msc=0 as glXSwapBuffers() request,
and called xcb_present_pixmap with invalid divisor=0, remainder=1
combo. The present extension responded kindly to this with a
BadValue error and dropped the request, but mesa's DRI3/Present
backend doesn't check for error codes. From there on stuff went
downhill quickly for the calling OpenGL client...
This patch fixes the problem.
v2: Change comments to be more clear, with reference to
relevant spec, as suggested by Eric Anholt.
Cc: "10.3 10.4" <mesa-sta...@lists.freedesktop.org>
Signed-off-by: Mario Kleiner <mario.kleiner...@gmail.com>
Reviewed-by: Axel Davy <axel.d...@ens.fr>
Reviewed-by: Eric Anholt <e...@anholt.net>
---
src/glx/dri3_glx.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
index 3f5e64c..1ddc723 100644
--- a/src/glx/dri3_glx.c
+++ b/src/glx/dri3_glx.c
@@ -1560,11 +1560,24 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t
target_msc, int64_t divisor,
dri3_fence_reset(c, back);
/* Compute when we want the frame shown by taking the last known
successful
- * MSC and adding in a swap interval for each outstanding swap request
+ * MSC and adding in a swap interval for each outstanding swap request.
+ * target_msc=divisor=remainder=0 means "Use glXSwapBuffers() semantic"
*/
++priv->send_sbc;
- if (target_msc == 0)
+ if (target_msc == 0 && divisor == 0 && remainder == 0)
target_msc = priv->msc + priv->swap_interval * (priv->send_sbc -
priv->recv_sbc);
+ else if (divisor == 0 && remainder > 0) {
+ /* From the GLX_OML_sync_control spec:
+ *
+ * "If <divisor> = 0, the swap will occur when MSC becomes
+ * greater than or equal to <target_msc>."
+ *
+ * Note that there's no mention of the remainder. The Present
extension
+ * throws BadValue for remainder != 0 with divisor == 0, so just drop
+ * the passed in value.
+ */
+ remainder = 0;
+ }
/* From the GLX_EXT_swap_control spec:
*
--
2.1.0
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