[Mesa-dev] Restrictions on redefine_user_buffer()

[Thomas Hellstrom]

Hi,

I've been working a bit on optimizing uploads of non-vbo vertex arrays 
on the svga device.
Since we have no knowledge of the vertex array size before a draw call 
and the vertex array may change values in between subsequent draw calls 
it's pretty pointless to upload the whole array to gpu memory. I 
basically want to upload only the vertices affected by each draw call.

Here's where redefine_user_buffer() comes in, but to be able to use it 
for this optimization we must require that a subsequent draw call 
referencing the user buffer must not access any data outside [offset, 
offset+size-1]. A stronger restriction than the comment in the 
p_context.h header file.

Any comments?

Thomas