demo · v137

Copy graph

Pick a frame budget and a copy strategy; the lab runs the same upload graph through the two overloads of copyBufferToBuffer. The new 3-arg form (whole buffer, no offsets) avoids the manual size = src.size - srcOffset arithmetic and the offhand bugs that come with it.

Heads upRequires Chrome 137+ with WebGPU enabled. Falls back to a CPU-side Uint8Array.set harness so the comparison runs in any browser.
probing…
legacy: 5-arg form

copyBufferToBuffer(src, srcOffset, dst, dstOffset, size)

// boilerplate to copy whole buffer
encoder.copyBufferToBuffer(
  src,         /* srcOffset */ 0,
  dst,         /* dstOffset */ 0,
  src.size               // easy to mistype
);
median frame time—
API-misuse risk5 args, easy to swap
v137: 3-arg overload

copyBufferToBuffer(src, dst, size?)

// no offsets — clearer intent
encoder.copyBufferToBuffer(src, dst);
// or with explicit length:
encoder.copyBufferToBuffer(src, dst, n);
median frame time—
API-misuse risk2 positional args

which overload do I want?

/* whole src -> whole dst */                encoder.copyBufferToBuffer(src, dst);
/* whole src -> whole dst, explicit size */ encoder.copyBufferToBuffer(src, dst, src.size);
/* sub-region */                            encoder.copyBufferToBuffer(src, 16, dst, 32, 256);
/* truncate src -> whole dst */             encoder.copyBufferToBuffer(src, 0, dst, 0, dst.size);

see also