[GRASS-dev] raster offset with cairo driver

[Lars Ahlzen]

Glynn Clements wrote:
> Hamish wrote:
> 
>> raster offset and fonts now look ok, good stuff guys.
>>
>> I've updated the fancy example on the wiki page to show off the fancy compass:
>>  http://grass.gdf-hannover.de/wiki/Cairo_driver#Examples
>>
>>
>> d.out.file now has added support for ps, svg, and pdf by way of the Cairo
>> driver.
>>
>> but it doesn't work, I get output like this for the simple spearfish example:
> 
> [snip]
> 
> It works for me. Where "works" means "renders everything then dumps
> the resulting raster image to a 14MiB PostScript file".

Cairo does have an unfortunate tendency to sometimes render to raster 
and embed that into the requested format, presumably as some kind of 
"last resort" when it (or the selected format) doesn't support some 
drawing operation.

I haven't done enough testing to figure out exactly when this happens or 
what triggers it.

> Well, that rules out using cairo for the core of the 7.x graphics
> architecture.

Perhaps. Then again,

* Depending on what the options are, it might be a lot easier to find 
those cases where Cairo goes into "raster rendering" mode and work 
around them or otherwise prevent them from happening. While this is not 
explicitly mentioned in the Cairo documentation (AFAIK), the Cairo 
developers (or the source) might be able to provide more insight.

* While Cairo is fairly mature today, I'm sure it will improve further 
before GRASS 7 is out. Some, or all, of these problems might even be 
gone by then. Especially if these issues are actually mentioned as a 
problem to the Cairo devs... :)

Granted, is hard to predict what will happen in the future, but at this 
point, I wouldn't entirely dismiss Cairo as an option.

Of course, that's just my two cents...

/ Lars

-- 
Lars Ahlzen
lars at ahlzen.com