Calculating the scissor rectangle fields with the y flipped (0 on top)
can generate negative values that will cause assertion failure later on
as the scissor fields are all unsigned. We must clamp the bbox values
again to make sure they don't exceed the fb_height. Also fixed a
calculation error.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108999
https://bugs.freedesktop.org/show_bug.cgi?id=109594
v2:
- I initially clamped the values inside the if (Y is flipped) case
and I made a mistake in the calculation: the clamp of the bbox[2] should
be a check if (bbox[2] >= fbheight) bbox[2] = fbheight - 1 instead and I
shouldn't have changed the ScissorRectangleYMax calculation. As the
fixed code is equivalent with using CLAMP instead of MAX2 at the top of
the function when bbox[2] and bbox[3] are calculated, and the 2nd is more
clear, I replaced it. (Nanley Chery)
v3:
- Reversed the CLAMP change in bbox[3] as the API guarantees that the
viewport height is positive. (Nanley Chery)
v4:
- Added nomination for the mesa-stable branch and the link to the second
bugzilla bug (Nanley Chery)
CC: <mesa-stable@lists.freedesktop.org>
Tested-by: Paul Chelombitko <qamonstergl@gmail.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
(cherry picked from commit
fd37a19ac4c8b2ebff330b2a06a7f311f7d478e3)
bbox[0] = MAX2(ctx->ViewportArray[i].X, 0);
bbox[1] = MIN2(bbox[0] + ctx->ViewportArray[i].Width, fb_width);
- bbox[2] = MAX2(ctx->ViewportArray[i].Y, 0);
+ bbox[2] = CLAMP(ctx->ViewportArray[i].Y, 0, fb_height);
bbox[3] = MIN2(bbox[2] + ctx->ViewportArray[i].Height, fb_height);
_mesa_intersect_scissor_bounding_box(ctx, i, bbox);