Mesa (10.4): glx/dri3: Request non-vsynced Present for swapinterval zero. (v3)

[Emil Velikov]

Module: Mesa
Branch: 10.4
Commit: ee241a688904211663e9445ed90e6d51aca3204f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ee241a688904211663e9445ed90e6d51aca3204f

Author: Mario Kleiner <mario.kleiner.de at gmail.com>
Date:   Fri Dec  5 08:42:31 2014 +0100

glx/dri3: Request non-vsynced Present for swapinterval zero. (v3)

Restores proper immediate tearing swap behaviour for
OpenGL bufferswap under DRI3/Present.

Cc: "10.3 10.4" <mesa-stable at lists.freedesktop.org>

v2: Add Frank Binns signed off by for his original earlier
patch from April 2014, which is identical to this one, and
Chris Wilsons reviewed tag from May 2014 for that patch, ergo
also for this one.

v3: Incorporate comment about triple buffering as suggested
by Axel Davy, and reference to relevant spec provided by
Eric Anholt.

Signed-off-by: Frank Binns <frank.binns at imgtec.com>
Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Axel Davy <axel.davy at ens.fr>
Reviewed-by: Eric Anholt <eric at anholt.net>
(cherry picked from commit 455d3036fab2c5da7e589644f12435fb104a69fc)

---

 src/glx/dri3_glx.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
index b89cb46..3f5e64c 100644
--- a/src/glx/dri3_glx.c
+++ b/src/glx/dri3_glx.c
@@ -1526,6 +1526,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
    xcb_connection_t *c = XGetXCBConnection(dpy);
    struct dri3_buffer *back;
    int64_t ret = 0;
+   uint32_t options = XCB_PRESENT_OPTION_NONE;
 
    unsigned flags = __DRI2_FLUSH_DRAWABLE;
    if (flush)
@@ -1565,6 +1566,17 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
       if (target_msc == 0)
          target_msc = priv->msc + priv->swap_interval * (priv->send_sbc - priv->recv_sbc);
 
+      /* From the GLX_EXT_swap_control spec:
+       *
+       *     "If <interval> is set to a value of 0, buffer swaps are not
+       *      synchronized to a video frame."
+       *
+       * Implementation note: It is possible to enable triple buffering behaviour
+       * by not using XCB_PRESENT_OPTION_ASYNC, but this should not be the default.
+       */
+      if (priv->swap_interval == 0)
+          options |= XCB_PRESENT_OPTION_ASYNC;
+
       back->busy = 1;
       back->last_swap = priv->send_sbc;
       xcb_present_pixmap(c,
@@ -1578,7 +1590,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t target_msc, int64_t divisor,
                          None,                                 /* target_crtc */
                          None,
                          back->sync_fence,
-                         XCB_PRESENT_OPTION_NONE,
+                         options,
                          target_msc,
                          divisor,
                          remainder, 0, NULL);