[PATCH xserver v3 23/24] xwayland: Cut off upper 32bit of queued vblank delay

[Roman Gilg]

This ensures the same behavior as in Present's fake counter and xfree86.

At the moment clients might do put vblanks too far into the future, because
the fake vblank code in Present and the xfree86 driver tolerate cut off upper
32bit due to an 64 to 32bit conversion. Do this therefore here as well to not
suddenly regress on Xwayland only.

The sample client, that triggers this behavior, is the Steam client.

Signed-off-by: Roman Gilg <subdiff at gmail.com>
---
 hw/xwayland/xwayland-present.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/xwayland/xwayland-present.c b/hw/xwayland/xwayland-present.c
index f403ff7..300d96f 100644
--- a/hw/xwayland/xwayland-present.c
+++ b/hw/xwayland/xwayland-present.c
@@ -299,6 +299,7 @@ xwl_present_queue_vblank(WindowPtr present_window,
 {
     struct xwl_window *xwl_window = xwl_window_of_top(present_window);
     struct xwl_present_event *event;
+    INT32 delay;
 
     if (!xwl_window)
         return BadMatch;
@@ -317,7 +318,10 @@ xwl_present_queue_vblank(WindowPtr present_window,
     event->event_id = event_id;
     event->present_window = present_window;
     event->xwl_window = xwl_window;
-    event->target_msc = msc;
+
+    /* Cut off upper 32bit, copies present_fake_queue_vblank. */
+    delay = (int64_t) (msc - xwl_window->present_msc);
+    event->target_msc = xwl_window->present_msc + delay;
 
     xorg_list_append(&event->list, &xwl_window->present_event_list);
 
-- 
2.7.4