emscripten-core/emscripten

glMapBufferData requires INVALIDATE_BUFFER?

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#6,692 opened on Jun 13, 2018

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Description

The emulation for glMapBufferRange requires MAP_WRITE and INVALIDATE_BUFFER here: https://github.com/kripken/emscripten/blob/a4d732f3094cfb2377609e1661044679f9c79734/src/library_gl.js#L1744

Under the hood, in glUnmapBufferData, the call is translated into a glBufferSubData. I don't think requiring INVALIDATE_BUFFER is correct here -- that means that the entire buffer should be discarded, not just the range that's mapped (which is INVALIDATE_RANGE). I think that:

  1. The requirement should be changed to INVALIDATE_RANGE
  2. A check should be done that there isn't an existing mapping for that buffer (additional restriction of only one range mapping per buffer, which GL doesn't have -- this could be relaxed with additional code, but probably not necessary in practice)

(Note I haven't tested any of this, this is just by code inspection from a question someone asked)

Contributor guide

Research direction
Examine the glMapBufferRange emulation in library gl.js and change the required flag from INVALIDATE BUFFER to INVALIDATE RANGE. Also add a check to ensure no existing mapping for that buffer.
Tech stack
javascript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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1-3 hours
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Clear
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GitJavaScript
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65