[Public WebGL] WebGL2 and no mapBuffer/mapBufferRange

Florian Bösch [email protected]
Wed Mar 4 09:54:58 PST 2015

There hasn't been a discussion on cutting that feature publicly. Though it
was probably known to the keen observer of the specification. Relevant
section here: https://www.khronos.org/registry/webgl/specs/latest/2.0/#5.14

Why have these functions been excluded?

mapBufferRange in particular is tied to a very useful construct which is
the MAP_UNSYNCHRONIZED_BIT. This allows an upload operation not to block on
the mapBufferRange call (although the subsequent unmapBuffer before use
would block, but you can perform other operations in the meantime or use
double-buffering to avoid intra-frame blocking). A future version of WebGL
might introduce GL_MAP_PERSISTENT_BIT as well, in which case buffers can be
used without having to unmap them before use. Overall mapping buffers
offers a variety of useful semantics to deal with data.

It'd be useful as preparation for programmers to get acquainted with
mapping buffer ranges in WebGL now, before it's got to be introduced later
on because it'll offer irresistible advantages to the specification editors.

Without knowing the reasons to cut this feature out, I'm going to assume
it's todo with pointers. I'd like to point out that both mapBuffer and
mapBufferRange return a pointer in native version, but both also expect a
size for this buffer to be specified. In WebGL, these calls could return an
array buffer instead of a pointer.
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