Why drawIndexed(indexCount) indexCount should > indexBuffer size?

[microaaron]

Description
indexCount needs to be larger than indexBuffer size to operate normally, otherwise an error will be reported.

Repro steps

...
    var indexBuffer = device.createBuffer({
      size:36*4,
      usage:GPUBufferUsage.INDEX | GPUBufferUsage.COPY_DST,
      label:`indexBuffer`,
    });
    device.queue.writeBuffer( indexBuffer, 0, new Uint32Array([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]), 0, 36 );
...
renderBundleEncoder.setIndexBuffer( indexBuffer, "uint32" );
renderBundleEncoder.drawIndexed( 36 );
...

Uncaptured WebGPU error: In a draw command, indexed:true indirect:false, caused by: Index 36 extends beyond limit 36. Did you bind the correct index buffer?

renderBundleEncoder.drawIndexed( 37 ); or larger will work properly.

This phenomenon only occurs in Firefox, in Chrome indexCount should <= indexBuffer size.

Expected vs observed behavior
Clearly describe what you get, and how it goes across your expectations.

Extra materials
Screenshots to help explain your problem.
Validation logs can be attached in case there are warnings and errors.
Zip-compressed API traces and GPU captures can also land here.

Platform
win10, Firefox Nightly 126.0a1

[Wumpf]

had a quick browse and indeed the max index limit is broken
https://github.com/gfx-rs/wgpu/blob/trunk/wgpu-core/src/command/bundle.rs#L169

it says if last_index <= index_limit {but should be if last_index > index_limit {

easy to fix, but needs to have a unit test added - concerning that this wasn't caught

[microaaron]

easy to fix, but needs to have a unit test added - concerning that this wasn't caught

Thanks. This function is very commonly used, please fix it as soon as possible.

[Wumpf]

likely won't get to it myself super soon. contributions welcome! :)