Premultiplication handled incorrectly for WebGL canvases display and upload

• Component: WebGL
• Status: RESOLVED DUPLICATE

[Kai Ninomiya]

Created attachment 429720 [details]
Reproduction case

1. Open https://codepen.io/kainino0x/pen/oNZwoJQ (or the attached file)

Expected result:
The six WebGL-rendered canvases should match the six 2d-rendered canvases (with the exception described in the test case).

Actual result:
See attached. From inspection, I think (but I'm not sure):
- Canvases with premultiplyAlpha:false are treated as if they have premultiplyAlpha:true
  (both when they are displayed, and when they are used as sources to texImage2D).
- texImage2D from webgl canvas sources with premultiplyAlpha:false are incorrectly y-flipped.

On macOS 11.3.1 (20E241):

- Pass: Chrome - 92.0.4515.7 (Official Build) canary (x86_64)
- Pass: Firefox - 90.0a1 (2021-05-18) (64-bit)
- FAIL: Safari Stable - Version 14.1 (16611.1.21.161.6)
- FAIL: Safari Technology Preview - Release 124 (Safari 14.2, WebKit 16612.1.11.10)

[Kai Ninomiya]

Created attachment 429721 [details]
Screenshot of the expected behavior (in Chrome, but Firefox is same)

[Kai Ninomiya]

Created attachment 429722 [details]
Screenshot of Safari Technology Preview's (incorrect) behavior

[Kimmo Kinnunen]

Thanks for the repro. I believe the bugs in depends on are the earlier reports of these.

[Radar WebKit Bug Importer]

<rdar://problem/78741173>

[Kimmo Kinnunen]

*** This bug has been marked as a duplicate of bug 200026 ***