Bitmap rendering Context for OffscreenCanvas

[fserb]

This change adds bitmaprenderingcontext to OffscreenCanvas.
The behaviour of the context is the same, just extending it to Offscreen.

@whatwg/canvas @Juanmihd

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[Juanmihd]

Addressed fserb comments; pull request ready to be reviewed.

[annevk]

Thanks for working on this! We'll also need:

1. Implementer support.
2. Tests.

[fserb]

Anne, we are working on the tests.

For support, can you help me get some Firefox folks on the thread?
I was hoping it was a small enough discussion, that we could have it here. But I can set up an issue for that too, wdyt?

[annevk]

It's fine here; @whatwg/canvas please indicate whether or not you support bitmap rendering context support for OffscreenCanvas. (Pinging WHATWG teams from OP does not work due to our bot unfortunately.)

[Juanmihd]

The tests are done!
web-platform-tests/wpt#16032

[fserb]

ping @whatwg/canvas ?

[annevk]

There's a couple minor things left still here.

[Juanmihd]

Hey @annevk, I've addressed the comments, and I've found out that I was missing one place to correctly add the bitmaprenderer option, so I've added those changes also.

Thanks againg for taking the time to review this changes!

[Juanmihd]

Hey @annevk, thanks again for all the reviews. This is my first time editing the specs and I have lots to learn. You're reviews are being very helpful for that.

I've reverted the explanation of the canvas getter, after what you commented and reading carefully the document, I think the original definition of the getter is correct both for "normal" canvas and an offscreen canvas.

[annevk]

Thanks, hopefully final nits.

[annevk]

@Juanmihd I'm not sure where the correct place is to give feedback on tests, given the automatically exported PR, so I'll do it here. It would be really good to have some test coverage for the origin-clean flag. In particular, put bitmaps on the context that are not origin-clean and then see that convertToBlob() throws, and that drawing the canvas on another canvas and then exporting somehow fails, etc.

[sideshowbarker]

heads-up @whatwg/documentation

[chrisdavidmills]

Recorded potential documentation need ar https://trello.com/c/N0hJJV95/129-2d-canvas-api

[Juanmihd]

@annevk I've added a new test to validate the origin-clean flag functionality with convertToBlob.

Do you have any other comments regarding the specs?

[annevk]

Do you have a link to the test?

[Juanmihd]

@annevk Here you have:
https://github.com/web-platform-tests/wpt/blob/0d8afd195a93f748a374fa4edfaad9118d51c47f/imagebitmap-renderingcontext/toBlob-origin-clean-offscreen.sub.html

[Juanmihd]

Are there any other comments to address before finalizing the review?

[annevk]

@Juanmihd thanks; though you want to use promise_rejects (part of the test API). (We should figure out a way to do test review better across repositories. I'll talk to @foolip about that.)

[annevk]

So I think we're still lacking these things

• Implementer interest
• Implementation bugs

right? Otherwise this looks good to me.

(@musgravejw you want to keep this in mind as this might end up clashing with your refactoring effort in #4565 or the other way around.)

[Juanmihd]

Test changed to use promise_rejects. https://github.com/web-platform-tests/wpt/pull/16032/files#diff-49891c9a9321f46e9402869e95b45261

Thanks @annevk.

I'll create now the Implementation Bugs.

[Juanmihd]

Firefox bug.
https://bugzilla.mozilla.org/show_bug.cgi?id=1548049

[Juanmihd]

WebKit bug.
https://bugs.webkit.org/show_bug.cgi?id=197421

[Juanmihd]

ping @whatwg/canvas? any comment to get the Implementer Interest?

[Juanmihd]

@annevk Can you help me pinging @whatwg/canvas? I think I'm doing it wrong.

[fserb]

Btw, this will soon be used by WebGPU as the main way of rendering context to screen: kainino0x/gpuweb#4

[annevk]

@Juanmihd they are already copied so should be getting emails either way. Might help to reach out to folks directly. For Mozilla you can also use https://github.com/mozilla/standards-positions. I'll add you to the WHATWG organization so you can ping teams in future issues. Do you also want to join the canvas team?

[grorg]

WebKit would like to implement this.

[Juanmihd]

@annevk Thanks for adding me to the whatwg organization! Yes, I'd like to join the canvas team, as it is my primary work here at Google.

And given that the implementers have shown interest, is there anything else to do prior to merging this change?

[annevk]

No, all good (and you're part of the team). Thanks all!