[Mesa-dev] [PATCH] meta: Clip src/dest rects in BlitFramebuffer.

[Chris Forbes]

Right, that makes good sense.

On Mon, Apr 14, 2014 at 11:28 PM, Marek Olšák <maraeo at gmail.com> wrote:
> For scaled blits, this is not correct. For example, if you blit a
> 10x10 texture to another 10x10 texture with horizontal scaling of
> 1.5x, the X texture coordinate of the rightmost pixel should be
> 6.666666. Mesa clip blit doesn't return floating-point coordinates of
> the source, so you can't use them. You can however take the clipped
> destination coordinates and set them as a scissor rectangle, keeping
> the original coordinates unmodified. That way, you'll get correct
> clipping (in hardware though) with correct source coordinates for
> scaled blits.
>
> See st_BlitFramebuffer.
>
> Marek
>
> On Mon, Apr 14, 2014 at 10:20 AM, Chris Forbes <chrisf at ijw.co.nz> wrote:
>> Nothing was bothering to clip the blit. If the src rect was partially
>> outside the framebuffer, we'd end up picking up more copies of the
>> edge texels due to clamping.
>>
>> Note that this is slight overkill -- we could get away with clipping src
>> only, since fragments outside the destination surface will be discarded
>> anyway.
>>
>> Fixes piglit's fbo-blit-stretch test on drivers which use the meta path.
>> (i965: should fix Broadwell, but also fixes Sandybridge/Ivybridge/Haswell
>> since this test falls off the blorp path now due to format conversion)
>>
>> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77414
>> ---
>>  src/mesa/drivers/common/meta_blit.c | 31 +++++++++++++++++++++++++------
>>  1 file changed, 25 insertions(+), 6 deletions(-)
>>
>> diff --git a/src/mesa/drivers/common/meta_blit.c b/src/mesa/drivers/common/meta_blit.c
>> index 31e494f..38d53ef 100644
>> --- a/src/mesa/drivers/common/meta_blit.c
>> +++ b/src/mesa/drivers/common/meta_blit.c
>> @@ -33,6 +33,7 @@
>>  #include "main/enable.h"
>>  #include "main/enums.h"
>>  #include "main/fbobject.h"
>> +#include "main/image.h"
>>  #include "main/macros.h"
>>  #include "main/matrix.h"
>>  #include "main/multisample.h"
>> @@ -590,12 +591,9 @@ blitframebuffer_texture(struct gl_context *ctx,
>>     return true;
>>  }
>>
>> -/**
>> - * Meta implementation of ctx->Driver.BlitFramebuffer() in terms
>> - * of texture mapping and polygon rendering.
>> - */
>> -void
>> -_mesa_meta_BlitFramebuffer(struct gl_context *ctx,
>> +
>> +static void
>> +_mesa_meta_blit_preclipped(struct gl_context *ctx,
>>                             GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
>>                             GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
>>                             GLbitfield mask, GLenum filter)
>> @@ -804,6 +802,27 @@ fallback:
>>     }
>>  }
>>
>> +/**
>> + * Meta implementation of ctx->Driver.BlitFramebuffer() in terms
>> + * of texture mapping and polygon rendering.
>> + */
>> +void
>> +_mesa_meta_BlitFramebuffer(struct gl_context *ctx,
>> +                           GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
>> +                           GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
>> +                           GLbitfield mask, GLenum filter)
>> +{
>> +   if (!_mesa_clip_blit(ctx, &srcX0, &srcY0, &srcX1, &srcY1,
>> +                        &dstX0, &dstY0, &dstX1, &dstY1)) {
>> +      /* nothing left! */
>> +      return;
>> +   }
>> +
>> +   _mesa_meta_blit_preclipped(ctx, srcX0, srcY0, srcX1, srcY1,
>> +                              dstX0, dstY0, dstX1, dstY1,
>> +                              mask, filter);
>> +}
>> +
>>  void
>>  _mesa_meta_glsl_blit_cleanup(struct blit_state *blit)
>>  {
>> --
>> 1.9.1
>>
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