[Mesa-dev] Blits with huge widths/heights

[Marek Olšák]

We could certainly increase the width and height to 32 bits for
pipe_blit_info, not pipe_box.

Marek
On Sat, Oct 6, 2018 at 4:01 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>
> There's a WebGL test here
>
> https://www.khronos.org/registry/webgl/sdk/tests/conformance2/rendering/blitframebuffer-size-overflow.html
>
> which does a fairly ridiculous blit:
>
>     srcX0=-1, srcY0=-1, srcX1=2147483647, srcY1=2147483647,
>     dstX0=-1, dstY0=-1, dstX1=2147483647, dstY1=2147483647
>
> The underlying src and dst textures are 8x8. We hit some precision
> issues in _mesa_clip_blit, but after fixing those, I run into the
> st_BlitFramebuffer logic which has this comment:
>
>    /* NOTE: If the src and dst dimensions don't match, we cannot simply adjust
>     * the integer coordinates to account for clipping (or scissors) because that
>     * would make us cut off fractional parts, affecting the result of the blit.
>     */
>
> That means that the height gets set to srcY0 - srcY1, which obviously
> overflows the int16_t.
>
> Is there any reasonable way of clipping it down without running into
> the fraction parts issue mentioned in the comment? Otherwise we have
> to go back to 32-bit height. (Not 100% sure that most drivers would do
> anything particularly reasonable here either...)
>
> Cheers,
>
>   -ilia