Leif Delgass wrote:
> 
> I just discovered that the glean failures in blendFunc, logicOp,
> orthoPosRandTris, orthoPosRandRects, orthoPosTinyQuads, and polygonOffset
> are the result of an off-by-one error in the y screen coordinates.  If I
> add one to the Y coordinate in the viewport conversion to screen
> coordinates, these tests all pass.  However, it breaks the scissor test
> and the orthoPos[H,V]Lines and orthoPosPoints tests still fail (which
> could be a result of the implementation of points and lines with
> triangles/quads).  It also seems to leave a row of pixels at the top of
> the window which isn't drawn on, but is cleared.  The stipple test still
> has the same problem because lines still aren't conformant.  I'm still a
> little puzzled as to where the off-by-one error actually originates, but
> this narrows down the problem a lot.

The Y-coordinate error may be less than one.  Most of the DRI hardware
drivers need X/Y coordinates biased by a small amount in order to make
hardware rasterization and software rasterization coincide.

So, something like 0.75 or 0.875 might work better.

-Brian



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