[Mesa-dev] [PATCH 09/24] swrast: Directly map the stencil buffer in read_stencil_pixels.

[Brian Paul]

On Fri, Oct 28, 2011 at 1:49 PM, Eric Anholt <eric at anholt.net> wrote:
> This avoids going through the wrapper that has to rewrite the data for
> packed depth/stencil.  This isn't done in _swrast_read_stencil_span
> because we don't want to map/unmap for each span.
> ---
>  src/mesa/swrast/s_readpix.c |   43 +++++++++++++++++++++++++++++++++++++++----
>  1 files changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/src/mesa/swrast/s_readpix.c b/src/mesa/swrast/s_readpix.c
> index 187c27e..4ecb5b8 100644
> --- a/src/mesa/swrast/s_readpix.c
> +++ b/src/mesa/swrast/s_readpix.c
> @@ -142,8 +142,10 @@ read_stencil_pixels( struct gl_context *ctx,
>                      const struct gl_pixelstore_attrib *packing )
>  {
>    struct gl_framebuffer *fb = ctx->ReadBuffer;
> -   struct gl_renderbuffer *rb = fb->_StencilBuffer;
> -   GLint j;
> +   struct gl_renderbuffer *rb = fb->Attachment[BUFFER_STENCIL].Renderbuffer;
> +   GLint j, i;
> +   GLubyte *map;
> +   GLint stride;
>
>    if (!rb)
>       return;
> @@ -151,18 +153,51 @@ read_stencil_pixels( struct gl_context *ctx,
>    /* width should never be > MAX_WIDTH since we did clipping earlier */
>    ASSERT(width <= MAX_WIDTH);
>
> +   ctx->Driver.MapRenderbuffer(ctx, rb, x, y, width, height, GL_MAP_READ_BIT,
> +                              &map, &stride);
> +
>    /* process image row by row */
> -   for (j=0;j<height;j++,y++) {
> +   for (j = 0; j < height; j++) {
>       GLvoid *dest;
>       GLstencil stencil[MAX_WIDTH];
>
> -      _swrast_read_stencil_span(ctx, rb, width, x, y, stencil);
> +      switch (rb->Format) {
> +
> +      case MESA_FORMAT_S8_Z24: {
> +        uint32_t *data = (uint32_t *)map;
> +        for (i = 0; i < width; i++)
> +           stencil[i] = data[i] >> 24;
> +        break;
> +      }
> +
> +      case MESA_FORMAT_Z24_S8: {
> +        uint32_t *data = (uint32_t *)map;
> +        for (i = 0; i < width; i++)
> +           stencil[i] = data[i] & 0xff;
> +        break;
> +      }
> +
> +      case MESA_FORMAT_S8:
> +        for (i = 0; i < width; i++)
> +           stencil[i] = map[i];
> +        break;

I'd probably put the code to unpack a row of stencil values into a new
_mesa_unpack_ubyte_stencil_row() function in format_unpack.c in case
it could be used elsewhere, like in the swrast stencil op code.

Otherwise this looks good.

-Brian