d8ce3ed140
Previously canceling a render done by the split kernel could cause artifacts such as very bright or dark tiles. This was caused by unfinished samples being included in the output buffer. To avoid this we now wait till all the currently rendering samples have finished, up to a limit of twice the expected time for them to finish (currently this is no more than 20 seconds, but usually its much less). If samples still haven't finished by then we stop anyways in case there's an endless loop occurring.