til_fb: return queue delay from til_fb_page_get()

til_fb is triple buffered, but when rendering lags behind the
queue is empty making present-to-delay intervals smaller than
when rendering is keeping up and the queue is kept full.

This returns the duration of the returned pages last
submit-to-present delay, effectively measuring how long a page
can expect to wait to be flipped to/presented currently.

A subsequent commit will apply this delay value to the ticks
supplied to rendering.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/main.c b/src/main.c
index e51ad5e..e8a166a 100644
--- a/src/main.c
+++ b/src/main.c
@@ -326,9 +326,9 @@ static void * rototiller_thread(void *_rt)
 	rototiller_t	*rt = _rt;
 
 	while (til_stream_active(rt->stream)) {
-		unsigned	ticks;
+		unsigned	ticks, delay = 0;
 
-		rt->fragment = til_fb_page_get(rt->fb);
+		rt->fragment = til_fb_page_get(rt->fb, &delay);
 		if (!rt->fragment) {
 			til_stream_end(rt->stream);
 			continue;