[Webkit-unassigned] [Bug 217377] Implement ANGLE version of WebGL layer snapshot copyImageSnapshotWithColorSpace

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=217377

--- Comment #3 from Kimmo Kinnunen <kkinnunen at apple.com> ---
As per my understanding, the old implementation used the back buffer, not the front buffer. This is on the grounds that there's no bind of any kind, so it expects to read what is bound. The front buffer is not bound ever. In fact, the old code did not have any concept of front buffer conceptually "inside OpenGL", so it can not be read by that read pixels. Front buffer it a CA layer holding a IOSurface. The only way it can be reading front buffer if it was, back in the day before prepareForDisplay, called during CA commit but before buffer swap. E.g. it would read the back buffer just before it became front buffer. However, even in this case it will either have read wrong frame buffers if client had bound something or alternatively left gl state wrong (by a bind that is not seen in the code). 

I couldn't find the call site, so I'd assume it is either dead code or CALayer Obj-C vfunc override which I'm not that familiar with at the moment.

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