[GRASS-dev] Cairo monitor driver

Lars Ahlzen lars at ahlzen.com
Tue Oct 23 21:12:27 EDT 2007

Glynn Clements wrote:
> Lars Ahlzen wrote:
>>>> I believe this means that pretty much all of drawing.c can go... 
>>> This should make the code significantly easier to understand. At the
>>> present time, the cairo driver is probably more useful as an example
>>> of how to use cairo than anything else.
>> Yes. I'll remove all of the set_drawing_op/finish_drawing_op code.
> I've done this.
>> Once (reasonably) feature complete and stable, the cairo driver could be 
>> a good alternative to the other monitors, however. I've used it for 
>> quite a while (before it was announced) and I've found it very useful. 
>> Then again, I may be somewhat biased... :)
> For now, I've just removed the offset.
> I've also added clipping and bitmaps.

That's great, although I was about ready to post a patch with the same 
features (as I said I would). Oh well... either way I appreciate your 
work on it.

Forgive my persistence, but I must insist that the offset is added to 
lines/polylines (for pixel based formats (PNG) only, of course). Lines 
with odd widths are disproportinally common due, among other things, to 
the fact that many d-modules do not offer control over the width of 
lines in their output (and always draw 1-unit wide lines). Adding the 
offset also produces output that is much closer to what is produced by 
other pixel-based monitor drivers. I've done a lot of testing with and 
without the feature, and IMO not including it severely limits the 
monitor's usefulness.

Technically, it's obviously trivial. I'll post a patch that adds this 
feature shortly.

/ Lars

Lars Ahlzen
lars at ahlzen.com

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