218186 2020-10-26 06:36:01 -0700 CanvasCaptureMediaStreamTrack enables WebGL drawing buffer preserving and changes clear semantics 2021-03-06 04:43:59 -0800 1 1 1 Unclassified WebKit WebGL WebKit Local Build Unspecified Unspecified NEW https://bugs.webkit.org/show_bug.cgi?id=218187 https://bugs.webkit.org/show_bug.cgi?id=217211 InRadar P2 Normal --- 1 kkinnunen webkit-unassigned dino jonlee webkit-bug-importer oldest_to_newest 1701434 0 kkinnunen 2020-10-26 06:36:01 -0700 CanvasCaptureMediaStreamTrack enables WebGL drawing buffer preserving This changes de-facto observable behavior, as websites expect rAF to prepare the drawing buffer for display. Web sites in general sometimes depend on the buffer clearing semantics. 1701435 1 kkinnunen 2020-10-26 06:38:43 -0700 Marking as blocking WebGL GPU Process work, since this is buggy that would need to be implemented in remote WebGL. This should be instead fixed by introducing a canvas monitoring callback for drawing buffer prepare and calling that before the buffer is being prepared for display. 1703494 2 webkit-bug-importer 2020-11-02 05:36:19 -0800 <rdar://problem/70946812> 1736774 3 kkinnunen 2021-03-06 04:43:59 -0800 So the purpose of the feature is to take the webgl canvas contents and send it through webrtc, if I understand correctly. What the implementation does is: 1) Turn on WebGL "preserve drawing buffer" flag of the webgl context. 2) Takes a snapshot of the webgl canvas contents at random point in time after each modification when the execution drops to main loop 3) send that picture over webrtc Steps 1 and 2 are not good.