[GRASS-dev] Cairo monitor driver

Lars Ahlzen lars at ahlzen.com
Thu Oct 25 18:01:15 EDT 2007

Glynn Clements wrote:
>> Good point. It makes sense to set the default line width to 1 unit, at
>> the very least for PNG output, to make sure it's consistent with the
>> behavior of other pixel-based monitors.
> Note that you cannot get consistency with XDRIVER; X intentionally
> doesn't specify the rendering of thin (zero width) lines, so that a
> hardware implementation can be used. IOW, zero width lines are
> rendered however the graphics chip decides to render them.

X may be an exception in that respect. Then again, have you ever used a 
system that didn't render them as 1 pixel lines? ;-)

>> Anyway, assuming that the default line width is 1 unit for pixel based
>> output (to be consistent), then the problem remains.
> At this point, it's largely moot.
> Integrating the cairo driver (e.g. modifying libraster to allow direct
> rendering via the cairo driver) is probably too destabilising a change
> now that 6.3 is at the release-candidate stage, so gis.m will likely
> continue to use the PNG driver.

It may be moot with respect to 6.3.

I just want to make the driver as useful as possible. Since I still 
don't see any downside implementing the offset (other than a few extra 
lines of code), but a significant benefit, I see no reason not to do so. 
It's by no means urgent, though.

> 7.x will use floating-point display coordinates throughout, so there
> will be no need for any offset.

True. This will be very nice indeed! Btw, do we expect more 6.x releases 
after 6.3, or will all work shift to 7.x?

/ Lars

Lars Ahlzen
lars at ahlzen.com

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