[Mesa-stable] [Mesa-dev] [PATCH V2 12/14] meta: Fix reading luminance texture as rgba in _mesa_meta_pbo_GetTexSubImage()

[Iago Toral]

The problem here is that the _mesa_meta_BlitFramebuffer is not setting
G/B channels to 0.0 when doing Luminance/Intensity to RGBA conversions,
so why not implement the fix in _mesa_meta_BlitFramebuffer directly? The
GL spec expects frambuffer blits to handle these conversions properly,
so it looks like a win for all uses of that function.

Iago

On Fri, 2015-07-17 at 10:28 -0700, Anuj Phogat wrote:
> After recent addition of pbo testing in piglit test getteximage-luminance,
> it fails on i965. This patch makes a sub test pass.
> 
> This patch adds a clear color operation to meta pbo path, which I think is
> better than falling back to software path.
> 
> V2: Fix color mask for GL_LUMINANCE_ALPHA
> 
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> Cc: <mesa-stable at lists.freedesktop.org>
> ---
>  src/mesa/drivers/common/meta_tex_subimage.c | 36 +++++++++++++++++++++++++++--
>  1 file changed, 34 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/drivers/common/meta_tex_subimage.c b/src/mesa/drivers/common/meta_tex_subimage.c
> index 13f8292..f4d5ac3 100644
> --- a/src/mesa/drivers/common/meta_tex_subimage.c
> +++ b/src/mesa/drivers/common/meta_tex_subimage.c
> @@ -28,6 +28,7 @@
>  #include "blend.h"
>  #include "bufferobj.h"
>  #include "buffers.h"
> +#include "clear.h"
>  #include "fbobject.h"
>  #include "glformats.h"
>  #include "glheader.h"
> @@ -278,8 +279,9 @@ _mesa_meta_pbo_GetTexSubImage(struct gl_context *ctx, GLuint dims,
>     int full_height, image_height;
>     struct gl_texture_image *pbo_tex_image;
>     struct gl_renderbuffer *rb = NULL;
> -   GLenum status;
> -   bool success = false;
> +   GLenum status, src_base_format;
> +   bool success = false, clear_channels_to_zero = false;
> +   float save_clear_color[4];
>     int z;
>  
>     if (!_mesa_is_bufferobj(packing->BufferObj))
> @@ -380,6 +382,27 @@ _mesa_meta_pbo_GetTexSubImage(struct gl_context *ctx, GLuint dims,
>                                    GL_COLOR_BUFFER_BIT, GL_NEAREST))
>        goto fail;
>  
> +   src_base_format = tex_image ?
> +                     tex_image->_BaseFormat :
> +                     ctx->ReadBuffer->_ColorReadBuffer->_BaseFormat;
> +
> +   /* Depending on the base formats involved we might need to rebase some
> +    * values. For example if we download from a Luminance format to RGBA
> +    * format, we want G=0 and B=0.
> +    */
> +   clear_channels_to_zero =
> +      _mesa_need_luminance_to_rgb_conversion(src_base_format,
> +                                             pbo_tex_image->_BaseFormat);
> +
> +   if (clear_channels_to_zero) {
> +      memcpy(save_clear_color, ctx->Color.ClearColor.f, 4 * sizeof(float));
> +      /* Clear the Green, Blue channels. */
> +      _mesa_ColorMask(GL_FALSE, GL_TRUE, GL_TRUE,
> +                      src_base_format != GL_LUMINANCE_ALPHA);
> +      _mesa_ClearColor(0.0, 0.0, 0.0, 1.0);
> +      _mesa_Clear(GL_COLOR_BUFFER_BIT);
> +   }
> +
>     for (z = 1; z < depth; z++) {
>        _mesa_meta_bind_fbo_image(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
>                                  tex_image, zoffset + z);
> @@ -392,6 +415,15 @@ _mesa_meta_pbo_GetTexSubImage(struct gl_context *ctx, GLuint dims,
>                                   0, z * image_height,
>                                   width, z * image_height + height,
>                                   GL_COLOR_BUFFER_BIT, GL_NEAREST);
> +      if (clear_channels_to_zero)
> +         _mesa_Clear(GL_COLOR_BUFFER_BIT);
> +   }
> +
> +   /* Unmask the color channels and restore the saved clear color values. */
> +   if (clear_channels_to_zero) {
> +      _mesa_ColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
> +      _mesa_ClearColor(save_clear_color[0], save_clear_color[1],
> +                       save_clear_color[2], save_clear_color[3]);
>     }
>  
>     success = true;