[Mesa-dev] [PATCH] Unified st_context::draw_vbo

[Keith Whitwell]

On Fri, 2010-07-16 at 11:10 -0700, Chia-I Wu wrote:
> Hi all,
> 
> This patch series replaces
> 
>   st_context::draw_arrays
>   st_context::draw_elements,
>   st_context::draw_arrays_instanced
>   st_context::draw_elements_instanced
>   st_context::draw_range_elements
> 
> by a single
> 
>   st_context::draw_vbo(struct pipe_context *pipe,
>                        const struct pipe_draw_info *info);
> 
> The series is too big in size and I have to push it to
> 
>   http://cgit.freedesktop.org/~olv/mesa/log/?h=gallium-unified-draw
> 
> Since the drivers no longer need to implement all the drawing
> variants, the diffstat says
> 
>  29 files changed, 359 insertions(+), 1061 deletions(-)
> 
> Its main user (st_draw_vbo) is also simplified.
> 
> There are 4 commits in the branch.  The first commit adds the new
> function prototype to the header file.  The second commit implements
> draw_vbo for all pipe drivers.  The third commit converts all state
> trackers (st/mesa, st/vega, and util_draw_vertex_buffer) to use
> draw_vbo.  The last commit removes all other variants from the
> interface.
> 
> This looks like a nice cleanup to have to me.  Suggestion?


If we're reorganising these interfaces, there are a couple of things I'd
like to see done differently.  In particular, within your draw_info
struct there are a couple of entities which are often better handled as
persistent state - namely the primitive mode and index buffer binding.

Right now we've got a single call which sets as much state as
glMultiDrawElementsIndexed, but which can only draw a single primitive.

The ways out of this situation are to either move state out of
per-primitive transaction, or to modify the interface to accept >1
primitive at a time.

My preference would be to move primitive mode & index buffer (and other
stuff too?) out of your info struct and turn them into new dynamic state
calls.  

Having done that, it may still be worth considering passing >1 of your
info structs to the new unified entrypoints...

Keith