Safari workaround breaks use of preinitialized GL contexts in library_webgl.js

[MarkCallow]

Somewhere between 2.0.15 and 2.0.17 code was added at line 586 of createContext() in library_webgl.js to workaround some Safari issue. This code tries to dereference the canvas argument to createContext and thus breaks use of preinitialized GL contexts. When using those you pass null as the canvas parameter.

The code that handles preinitialized contexts is at line 621. Presumably the fix is as simple as moving the Safari workaround to the else after line 621, the not-preinitialized case. But I don't have enough familiarity with the webgl library to feel comfortable providing a PR.

This has broken my JS KTX v2 decoder (including Basis Universal) and WebGL uploader. My users are naturally complaining to me. Please fix it as soon as possible.

[kripken]

git blame says that line came from @juj 's change #13659

[juj]

When using those you pass null as the canvas parameter.

The intended usage of using preinitialized context has not been to pass null as the canvas parameter, but instead, the intended usage is to pass the canvas that the preinitialized context was derived from. This is tested under browser.test_preinitialized_webgl_context test.

That being said, posted PR #13979 to adapt to this new expectation. If you'd like to ensure that your code pattern of calling GL.createContext() with a null canvas stays working, please contribute a test that stresses that behavior.

[MarkCallow]

I no longer recall where I got the idea I had to pass null, probably from some example I found. I have now modified my app to pass the canvas though, since the pre-initialized GL context is tightly coupled to the canvas, it does seem unnecessary. If I can find time I will contribute a test for this pattern.

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant.