sna/dri: Disable TripleBuffering by default for compositors

Ideally, the method of swapping is something that the applications have
control over, along with how to synchronise to the vertical refresh.
Whilst triple buffering is good to reduce jitter for games (at the cost of
an extra frame of latency, usually considered a good tradeoff), it
prevents the applications from accurately controlling the presentation
of animations. One vocal critique is Owen Taylor, who demands accurate
swap control for smooth animations in gnome-shell. For example,

http://blog.fishsoup.net/2012/11/28/avoiding-jitter-in-composited-frame-display/

In lieu of application control, just apply a quirk for the compositor.
Everyone else will just have to wait for DRI3.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/sna/sna_driver.c b/src/sna/sna_driver.c
index 16dbc91b..fc8773bc 100644
--- a/src/sna/sna_driver.c
+++ b/src/sna/sna_driver.c
@@ -77,6 +77,7 @@ DevPrivateKeyRec sna_pixmap_key;
 DevPrivateKeyRec sna_gc_key;
 DevPrivateKeyRec sna_window_key;
 DevPrivateKeyRec sna_glyph_key;
+DevPrivateKeyRec sna_client_key;
 
 static void
 sna_load_palette(ScrnInfoPtr scrn, int numColors, int *indices,
@@ -788,6 +789,10 @@ sna_register_all_privates(void)
 	if (!dixRegisterPrivateKey(&sna_window_key, PRIVATE_WINDOW,
 				   3*sizeof(void *)))
 		return FALSE;
+
+	if (!dixRegisterPrivateKey(&sna_client_key, PRIVATE_CLIENT,
+				   sizeof(struct sna_client)))
+		return FALSE;
 #else
 	if (!dixRequestPrivate(&sna_pixmap_key, 3*sizeof(void *)))
 		return FALSE;
@@ -800,6 +805,9 @@ sna_register_all_privates(void)
 
 	if (!dixRequestPrivate(&sna_window_key, 3*sizeof(void *)))
 		return FALSE;
+
+	if (!dixRequestPrivate(&sna_client_key, sizeof(struct sna_client)))
+		return FALSE;
 #endif
 
 	return TRUE;