Re: [AD] OpenGL path for WebGL

[MaxEd <max.savenkov@xxxxxxxxxx>]

> Please ask on the [AD] list (http://www.liballeg.org/maillist.html), not
> here. Developers are not usually subscribed to this list here (it was
> basically superceded by allegro.cc a decade or so ago :P). I'll be
> forwarding this to the correct list, and hopefully someone who knows more
> about OpenGL than me can answer in more detail.

I can't for the life of me understand how to reply to reposted message, so I'll start a new thread, I guess. I don't understand mailing lists :) Forums are so much nicer...

> > 1) Why does Allegro uses Vertex Buffer Arrays? There is only one
> > Vertex Buffer Object, and every frame we bind it and enable its
> > attributes. I'm do not know much about OpenGL, but it seems to me that
> > we should either do all these things, OR use VBA, which saves state.
> > To test this, I disabled creation & usage of VBA, and everything
> > worked without any glitches.
>
> How did you test?

By running 'skater' demo.

> > 2) I disabled emulation of WebGL's absent OpenGL ES 2 features in
> > Emscripten, and now, while the test is running, there are some
> > rendering errors. It seems they are related to Primitives addon.
> > Particularly this code inside setup_state function in prim_opengl.c
> > spews errors into console ("vertexAttribPointer: must have valid
> > GL_ARRAY_BUFFER binding"):
> Is this with or without removing the vertex buffer array code above? I can
> see this before calling setup_state:
> if (vertex_buffer) {
>   glBindBuffer(GL_ARRAY_BUFFER, (GLuint)vertex_buffer->common.handle);
> }
> So the vertex array buffer should be bound at the time
> glVertexAttribPointer is called.

This is after disabling VBA code (because while it is enabled I can't even compile anything, because there is no glGenVertexArrays function in WebGL)
This branch only gets called if there is vertex_buffer passed into draw_prim_raw, which only happens when somebody calls al_draw_vertex_buffer. But which buffer should be bound when al_draw_prim is called, which does not have user-specified VBO?