Printing with xlib & art backend

[Riccardo Mottola]

Hi,

I think this has mostly to do with Eric's optimisations about 2 years ago.
Riccardo Mottola wrote:
> > Printing error: <NSException: 0x84762e4> 
> > NAME:NSInvalidArgumentException 
> > REASON:[GSStreamContext-GSDefineGState] not implemented INFO:(null)
GSStreamContexts does not implement GSDefineGState explicitely, throwing 
an exception.

During Eric's refactor, a lot of code was moved from NSImage to 
NSImageRep, but also PS operation were substituted with DPS operation, 
which do require gState though.

Thus my educated guess is that printing images is broken since that time 
except on cairo

I had the idea of using supportsDrawingGState to skip, but it is 
incorrect and it will break, as then DPSComposite doesn't work.

Ideas?

Riccardo