[Webkit-unassigned] [Bug 219023] Blank glReadPixels since iOS 14.2

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=219023

paul at sketchfab.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #5 from paul at sketchfab.com ---
somehow fixed if canvas is transparent, not if canvas is opaque

transparent canvas => 

https://jsfiddle.net/sketchfab/ej87khya/
for just embed test on ios https://jsfiddle.net/sketchfab/ej87khya/show


opaque canvas => 

https://jsfiddle.net/sketchfab/gw3xh29f/
for just embed test on ios https://jsfiddle.net/sketchfab/gw3xh29f/show

In sketchfab js webgl code, transparent/opaque canvas path implications are just that we enable the alpha option in the canvas context creation.

So it doesn't work if we switch that option "off"
here is out context creation code, with comment on the option switch ("on" it works, "off" it breaks, same exact code for the rest of application)


in our case, complete code is doesn't work with:

```
const gl = canvas.getContext('webgl', {
            powerPreference: 'high-performance',
            antialias: false, 
            depth: false,
            stencil: false,
            alpha: off, // <= switching that off but rest exact same breaks screenshotting
            premultipliedAlpha: true,
            fullscreen: false,
            preserveDrawingBuffer: false
});
```

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