Add support for WebGL extension EXT_texture_norm16.

[juj]

To land once https://www.khronos.org/registry/webgl/extensions/EXT_texture_norm16/ is ratified.

CC @kainino0x @kenrussell.

[juj]

Is there an ETA to when EXT_texture_norm16 should appear? We have a quarterly deadline coming up really soon, and I am looking to update Emscripten for that. It would be great to have this in there if it's possible that EXT_texture_norm16 would ship in Chrome within the next three months, otherwise our adoption would be delayed by six months.

I wonder if there is any possiblity even that the extension would change in any way, since it is a carbon copy of the native GLES extension - perhaps we should just land this already now anticipating that it will go in in this form?

[kainino0x]

@shrekshao

[shrekshao]

Thanks Kai and Ken for pinging.

Is there an ETA to when EXT_texture_norm16 should appear?

I'm positive in landing EXT_texture_norm16 in WebGL 2 in Chrome soon since we've solved the major issues with workaround in ANGLE. We are now working on some copy texture issue with certain format combinations on certain Platforms revealed by chromium bots. Three months should be absolutely sufficient time. I'm looking forward to getting it landed in Chromium for WebGL 2 within this week. You should see an update in Chromium issue 1000354 when integration into Chromium is landed.
We still plan to get it supported in WebGL 1 as well in the near future.

I wonder if there is any possiblity even that the extension would change in any way

Yes it is a mostly a direct mirror of the corresponding GLES extension. There shouldn't be any major changes.
There is one potential update related to some disclaimer on color-renderability that might be added to the spec though. (ESSL 100 shader output precision is insufficient for 16bit normalized integer Jeff's comment). This should have no affect on the enums you are adding in this pull request.

[kainino0x]

+1 from me to go ahead and land this.

[juj]

Great, thanks for the update! Let's land this in.

[kenrussell]

Great! Excited to see this getting supported in Emscripten apps!

Let's test this on Chrome Canary as soon as the WebGL extension is available there. Please report any bugs to @shrekshao and me; thanks!

[shrekshao]

Oh no... I ran into this as I was looking for implementation reference for adding WEBGL_multi_draw to emscripten. Apologize for the delay not closely tracking this issue.

We've cleared the implementation issue in Chrome (http://crbug.com/1000354) and we reached an agreement at a WebGL WG in March to only expose EXT_texture_norm16 to WebGL 2 and promoted to community approved. I've just sent an issue to Jeff at Mozilla so hopefully we can see this extension moved to public soon.