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

[Keith Packard]

Adam Jackson <ajax at nwnk.net> writes:

> Is there some reason you believe GL's rasterisation rules for lines
> match fb's zero-width lines? Section 14.5.1 of the 4.5 spec looks quite
> a bit looser than fb to me.

I think they're 'good enough'; there aren't any rules requiring
particular rasterization for either, the only thing X requests is that
'not last' cap mode not draw the last pixel. afaict, GL suggests 'not
last' as the only option. It sounds like some drivers are doing both
'not last' and 'not first' though?

The more serious problem is that dashing isn't working, and that's just
bugs (either driver or glamor) as dashing is done in the fragment
shader.

I guess we could just run some tests at server startup to see what kind
of rasterization the driver was performing and compensate? Do a survey
of current results and try to come up with some bright-line tests to
distinguish between them, maybe bailing to MI if we get inconsistent results?

-- 
-keith
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