[PATCH 4/4] present: sync flips unless requested not to

[Frank Binns]

When the display driver supports async flipping this mode of operation
is always used. This means that, when the swap interval is none 0, the
present extension relies on vblank events to get synchronised flips.
However, by the time present gets the event, requests a flip and the GPU
has finished we might have missed the vblank period. This results in
tearing.

Fix this by always doing synced flips unless the client uses the
PresentOptionAsync flag when presenting a pixmap.

Signed-off-by: Frank Binns <frank.binns at imgtec.com>
---
 present/present.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/present/present.c b/present/present.c
index 32160b9..ec9f457 100644
--- a/present/present.c
+++ b/present/present.c
@@ -693,7 +693,7 @@ present_pixmap(WindowPtr window,
             }
         } else {
             target_msc = crtc_msc;
-            if (!(options & PresentOptionAsync))
+            if (!(options & PresentOptionAsync) || !screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
                 target_msc++;
         }
     }
@@ -768,7 +768,7 @@ present_pixmap(WindowPtr window,
     vblank->notifies = notifies;
     vblank->num_notifies = num_notifies;
 
-    if (!screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
+    if (!(options & PresentOptionAsync) || !screen_priv->info || !(screen_priv->info->capabilities & PresentCapabilityAsync))
         vblank->sync_flip = TRUE;
 
     if (pixmap && present_check_flip (target_crtc, window, pixmap, vblank->sync_flip, valid, x_off, y_off)) {
@@ -797,7 +797,7 @@ present_pixmap(WindowPtr window,
 
     xorg_list_add(&vblank->event_queue, &present_exec_queue);
     vblank->queued = TRUE;
-    if (target_msc >= crtc_msc) {
+    if (target_msc > crtc_msc) {
         ret = present_queue_vblank(screen, target_crtc, vblank->event_id, target_msc);
         if (ret != Success) {
             xorg_list_del(&vblank->event_queue);
-- 
1.8.5.4.gfdaaaa2