Make GPUBufferBinding size optional

[beaufortfrancois]

How about making GPUBufferBinding size optional? If not specified, it would be the same as the buffer size passed in the binding resource of device.createBindGroup()?

I believe this would make code easier to read and digest for newcomers.

    const gpuBufferSize = 4;
    const gpuBuffer = device.createBuffer({
      size: gpuBufferSize,
      usage: GPUBufferUsage.STORAGE
    });

    const bindGroup = device.createBindGroup({
      layout: bindGroupLayout,
      bindings: [
        {
          binding: 0,
          resource: {
            buffer: myGpuBuffer,
-           size: gpuBufferSize
          }
        }
      ]
    });

[kvark]

Vulkan has VK_WHOLE_SIZE for this, so default makes sense...

[kainino0x]

Makes sense to me, I think we talked about this once before too.

My only concern is that we should try to avoid making a distinction between undefined and 0. IMO it would be fine for the default to be 0, and 0 is a special value meaning to use the whole buffer size.

[beaufortfrancois]

Having a size of 0 that means the whole buffer size doesn't seem right to me. I fail to find some examples of this usage in Web APIs.

I would go with the IDL below.

 dictionary GPUBufferBinding {
     required GPUBuffer buffer;
     u64 offset = 0;
-    required u64 size;
+    u64? size;
 };

If size is not defined, use the whole size of the buffer.
Otherwise use same rules as before. 0 is still a valid value.

[kainino0x]

Are there examples of Web APIs making a distinction between undefined and 0?

If we want to avoid distinguishing undefined and 0, could have a special value like in Vulkan:

enum GPUBufferBindingSize { "whole-size" };
dictionary GPUBufferBinding {
    required GPUBuffer buffer;
    u64 offset = 0;
    (GPUBufferBindingSize | u64) size = "whole-size";
};

[beaufortfrancois]

This (GPUBufferBindingSize | u64) trick is still yet another way of saying that undefined gets treated as "whole-size". We're basically still distinguishing undefined and 0 there.

I made a mistake though. We should remove the ?, as null should just be treated as 0. undefined should be the only special value. Then, it should be:

 dictionary GPUBufferBinding {
     required GPUBuffer buffer;
     u64 offset = 0;
-    required u64 size;
+    // If size is undefined, use the whole size of the buffer.
+    u64 size;
 };

If size is undefined, use the whole size of the buffer.
Otherwise use same rules as before. 0 is still a valid value.

[kainino0x]

You're right that my suggestion still distinguishes 0 and undefined. Good point.

Your last suggestion looks good to me. Would you open a PR for it?

[beaufortfrancois]

@kainino0x Here's the PR: #346