[Public WebGL] Requirements for bufferData don't make sense given the IDL

Boris Zbarsky [email protected]
Mon Apr 2 11:20:14 PDT 2012

On 4/2/12 2:01 PM, Gregg Tavares (勤) wrote:
>     But the IDL declarations for this method don't allow |data| to be
>     null; an attempt to pass null will throw during the WebIDL overload
>     resolution algorithm.  Was this requirement meant to be on
>     bufferSubData (which does allow null to be passed)?  Or is
>     bufferData supposed to have an overload that allows null?
> bufferData should (and does) take null

Here's the relevant IDL at 
https://www.khronos.org/registry/webgl/specs/latest/#5.14 :

     void bufferData(GLenum target, GLsizeiptr size, GLenum usage);
     void bufferData(GLenum target, ArrayBufferView data, GLenum usage);
     void bufferData(GLenum target, ArrayBuffer data, GLenum usage);

If null is passed as tehe second argument, the second and third 
overloads will not be invoked, because they don't allow null (there's no 
'?' anywhere there).  GLsizeiptr is a typedef for long long, so we end 
up at http://dev.w3.org/2006/webapi/WebIDL/#es-long-long , invoke 
ToNumber(null), get +0, and invoke the first overload with 0 as the 
second argument.  But the text about what should happen when null is 
passed is only scoped to the second and third overload in the spec, so 
it still doesn't make sense.

At least that's what the spec says now.  Maybe there was _supposed_ to 
be a '?' on the second or third overload.  If so, it needs to be added 

> bufferSubData does not take null

Again, quoting the IDL in the spec right now:

     void bufferSubData(GLenum target, GLintptr offset, ArrayBufferView? 
     void bufferSubData(GLenum target, GLintptr offset, ArrayBuffer? data);

Clearly the third argument accepts null.  Again, maybe it's not supposed 
to; then the spec should be fixed accordingly, of course.


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