[cairo] Creating CMYK and spot colors using Postscript backend

[Bill Spitzak]

Craig Ringer wrote:
> Bill Spitzak wrote:
> 
>> In general, throwing errors or producing no output makes graphics
>> programs extremely fragile and bug-prone and should never be done if at
>> all possible. Another example is that poorly-formed UTF8 should draw as
>> many glyphs as possible and must always draw a box or something for
>> every erroneous byte.
> 
> In both those cases, as an application developer I'd be happy if the
> graphics code produced output (even bad output) - but *told* me that it
> was incorrect. However, it'd be extremely frustrating to have silent
> failures and mis-rendering.

Yes I agree, if you could query Cairo and have it tell you if something 
went wrong, that would be very useful. However it should still do the 
best-effort output and it should not prevent further rendering calls 
from working. Ie. an error can turn on an error flag but this has no 
other effect other than making the error query return true.