[PATCH xserver] glamor: Paint first and last pixel of lines

[Keith Packard]

Max Staudt <mstaudt at suse.de> writes:

> OpenGL implementations are allowed to be imprecise in drawing line caps.
> This patch expands on the original workaround in dc9fa908.

Yeah, finding a way to work around GL differences seems like a good
idea. In this case, however, I think you're fixing some drivers and
breaking others -- when drawing with non-idempotent raster
ops.

Idempotent raster ops are those for which multiple draws generate the
same result, like GXcopy; hence non-idempotent operations are those
which do not, such as GXxor.

I'm not sure what we should do here; there's no requirement in the
protocol that we do anything at all as the server is allowed to draw
pretty much whatever it wants for zero-width lines.

If you've found specific problems with Mesa drivers, I'd suggest we
actually go fix those instead of working around them in the X
server. The GL spec seems pretty clear in what it wants, and I think
that aligns with what the X server currently expects.

-- 
-keith
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