Intent to Ship: WebGPU: Texture and Sampler Lets

[Chromestatus]

Contact emails

dsin...@google.com

Explainer

No information provided

Specification

https://github.com/gpuweb/gpuweb/pull/5389

Summary

Add a language feature to WGSL, `texture_and_sampler_let` that adds the ability to store texture and sampler objects into a let declaration in WGSL.

Blink component

Blink>WebGPU

Web Feature ID

webgpu

Motivation

To allow storing texture and samples in WGSL shaders into lets. This allows creating local names for what are usually global objects.

Initial public proposal

https://github.com/gpuweb/gpuweb/issues/5339

TAG review

No information provided

TAG review status

Pending

Risks

Interoperability and Compatibility

This feature has been approved in W3C GPU for the Web WG meetings including participants from Safari and Firefox. Meeting minutes: https://docs.google.com/document/d/1kTmVO9okQZOotWtCNDzRaF-rPXgyIVJ-u5PEe7rnjQc/edit?tab=t.0#bookmark=id.u8bh2sfreh45

Gecko: No signal Mozilla members have approved https://github.com/gpuweb/gpuweb/pull/5389 and requested during weekly standardization meetings that we postpone filing standard positions until we reach Candidate Recommendation (CR) status in Q4.

WebKit: Closed Without a Position (https://github.com/WebKit/standards-positions/issues/294#issuecomment-1877411933)

Web developers: No signals

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

No information provided

Debuggability

No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No
All platforms will eventually have support. Will immediately be available on Android, Android WebView, ChromeOS, Mac, and Windows, where hardware support is available. Linux is planned to have WebGPU support in the future, so this feature will become available when WebGPU does.

Is this feature fully tested by web-platform-tests?

Yes
WebGPU/WGSL have a conformance test suite (https://github.com/gpuweb/cts) that is regularly pulled into Chromium and part of the testing of Dawn/Tint in Chromium. While the CTS can be embedded in WPT, the WebGPU team opted to keep it separate in Chromium testing to use a customized harness for robustness and performance. CTS: https://github.com/gpuweb/cts/pull/4490

Flag name on about://flags

No information provided

Finch feature name

UnsafeWGSLFeatures

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://crbug.com/459500757

Estimated milestones

Shipping on desktop	146
Shipping on Android	146
Shipping on WebView	146

Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).

No information provided

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5102334940151808?gate=6582632798355456

This intent message was generated by Chrome Platform Status.

[Yoav Weiss (@Shopify)]

LGTM1

[Vladimir Levin]

LGTM2

[Alex Russell]

Dumb question from a non-WGSL developer: what does this enable? Why do we want it? There's no explainer and no example code in the linked PR:

https://github.com/gpuweb/gpuweb/pull/5389/files

Are we going to be shipping this first?

[dan sinclair]

The issue linked from the PR provides more context: https://github.com/gpuweb/gpuweb/issues/5339. Essentially, it enables, inside a WGSL shader, to take a texture/sampler variable and assign it into a `let`. Basically provides an alternate name at the moment. In the future, the bindless work will have methods which can return a texture or sampler and we'd like to be able to store those into local variables.

So, this allows you to have have something like:

```

@group(0) @binding(0) var tex: texture_2d<f32>;

@fragment fn main() {
    let a = tex;
    var res: vec4f = textureLoad(a, vec2i(1i), 0);
}

```

With bindless it will become a bit more interesting (below is not finalized, still in discussion API, but works as an example):

```

@fragment fn main() {

  let a = getResource<texture_2d<f32>>(2);

```

removing the need to call `getResource` multiple times.

Not sure what you mean by going to be shipping this first? We've landed the code in Chrome behind the enable-unsafe-webgpu flag. So, it will be accessible from Chrome if the flag is enabled.

dan

[Alex Russell]

Thanks for all of this, Dan. Very helpful.

In terms of "going first", the question is "are we going to be the first engine to ship this to stable?"; that situation creates more risk for us, so we dot i's and cross t's even harder in those cases. Is it reasonable from your perspective to draft a small explainer if we are, indeed, going to be taking this risk?

Thanks

[dan sinclair]

The issue on github is, from our perspective, the explainer link (I realized I put the link in the Initial Public Proposal field instead of the Explainer field, sorry about that, I mis-understood what went where in the status dashboard.) I've fixed the link to act as the explainer at this point.

This is how we've been handling the other language features for WGSL so far. There is a requirement for any language feature, before it lands in the spec, that each of Mozilla, Apple and Google have agreed that we'll all implement the language feature, if we don't have that agreement then it doesn't land in the spec.

dan

[Rick Byers]

The github issue seems clear enough to me as an explainer given the small incremental nature and multi-implementer support. LGTM3

--
You received this message because you are subscribed to the Google Groups "blink-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+...@chromium.org.
To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAMYH%3DOghv1DV-96VbGsWCGO6NCtGz1iR0NQP7iM5w22dscguMg%40mail.gmail.com.