[cairo] A hidden offset for the xlib backend

[Jost Boekemeier]

[I've corrected the subject, sorry for that]

> A transient xlib-backend 
> surface *is* a transient pixmap.

It wraps one, yes.


> Because then application programmers have to start
> worrying 
> about the difference between "expose event
> coordinate space" 
> and the "window coordinate space". 

The cairo surface simply starts at 0/0; you currently
can't give it an offset.

One solution would be to extend the cairo API to
create a surface with the appropriate offset:

 cairo_surface_create(ct, event.xoff, event.yoff,
                          event.width, event.height);

Another option would be to require that the
programmer's normalize themselfs[1].  


Jost

[1] Wirth designed Oberon, the successor of Modula, so
that all arrays have a fixed lower bound: [0..N-1]. 
Programming with these arrays turned out to be easier
than the more expressive Modula arrays [MIN..MAX],
even though it requires that the programmers must
normalize themselfs.



	

	
		
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