APIs which take a ptr (ptr void) generated only as (ptr void)

[edwintorok]

For example the params here is an output, but in the OCaml API it seems to be only an input:
void glGetBufferPointerv(GLenum target, GLenum pname, GLvoid ** params);
val get_buffer_pointerv : enum ->
enum -> (nativeint, Bigarray.nativeint_elt) bigarray -> unit

[dbuenzli]

Yes, the reasons are that:

1. I was too lazy to bind it manually
2. If you want performance you don't specify pointers directly but use buffer objects, so what you get it here is the integer offset, mostly like 0 that you specified in glVertexAttribPointer (hence the bigarray of nativeint)
3. If you want performance you avoid to glGet* as much as possible anyway
4. If you really want the pointer you can still convert that integer to a pointer using ocaml-ctypes.

A warning was supposed to be written in the docs for the 5 cases where this happens, but I forgot it for glGet BufferPointerv, glGetPoinzerv, glGetVertexAttribPointerv. It's there for glMultiDrawElements and glMultiDrawElementsBaseVertex.

[dbuenzli]

Mmmh in fact it seems I'm wrong on 2) what you get here is a pointer on the mapped buffer, if it's mapped.

Ok so I may need to change it and return a bigarray instead, this means we need to add size parameter (i.e. the client has to know the size, see e.g. map_buffer vs. glMapBuffer). I'll also check for the other Get_Pointer. For the glMultidrawElements_ functions you may want to have a look at the warning in the docs.

That said I'm not sure I see the rationale for that function (or I'm missing something) as it allows other parts of the system to access a mapped buffer without the part that is mapping/unmapping actually knowing it. That seems a recipe for crashes, since the pointer becomes invalid once unmapped.

[edwintorok]

Look like glGetBufferPointerv should return the same pointer that glMapBuffer returned to you initially. I don't really see a use-case for it either (unless you forgot to save the pointer returned by glMapBuffer), so maybe just comment it out for now in the generated file.