compositor, backends: weston_compositor_read_presentation_clock
Create a new function weston_compositor_read_presentation_clock() to
wrap the clock_gettime() call for the Presentation clock.
Reading the presentation clock is never supposed to fail, but if it
does, this will notify about it. I have not seen it fail yet, though.
This prepares for new testing features in the future that might allow
controlling the presentation clock. Right now it is just a convenience
function for clock_gettime().
All presentation clock readers are converted to call this new function
except rpi-backend's rpi_flippipe_update_complete(), because it gets its
clock id via a thread-safe mechanism. There shouldn't be anything really
thread-unsafe in weston_compositor_read_presentation_clock() at the
moment, but might be in the future, and weston core is not expected to
need to be thread-safe.
This is based on the original patch by
Cc: Derek Foreman <derekf@osg.samsung.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/src/compositor.c b/src/compositor.c
index 60b7ee4..e060be1 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -4618,6 +4618,39 @@
return -1;
}
+/** Read the current time from the Presentation clock
+ *
+ * \param compositor
+ * \param ts[out] The current time.
+ *
+ * \note Reading the current time in user space is always imprecise to some
+ * degree.
+ *
+ * This function is never meant to fail. If reading the clock does fail,
+ * an error message is logged and a zero time is returned. Callers are not
+ * supposed to detect or react to failures.
+ */
+WL_EXPORT void
+weston_compositor_read_presentation_clock(
+ const struct weston_compositor *compositor,
+ struct timespec *ts)
+{
+ static bool warned;
+ int ret;
+
+ ret = clock_gettime(compositor->presentation_clock, ts);
+ if (ret < 0) {
+ ts->tv_sec = 0;
+ ts->tv_nsec = 0;
+
+ if (!warned)
+ weston_log("Error: failure to read "
+ "the presentation clock %#x: '%m' (%d)\n",
+ compositor->presentation_clock, errno);
+ warned = true;
+ }
+}
+
WL_EXPORT void
weston_version(int *major, int *minor, int *micro)
{