Re: Where's polygon odd/even fill mode?

[Owen Taylor <otaylor redhat com>]

On Thu, 2003-08-14 at 20:10, Tor Lillqvist wrote:

>  > On windows the SetPolyFillMode method accomplishes the
>  > same thing by setting the fill mode to WINDING. 
>
>  > Where's the same capability in GDK? 
>
> There doesn't seem to be... For some reason that functionality was
> left out of GDK. Quite possibly it was just an oversight when GDK was
> initially written, at which time it was just a rather thin wrapping
> over Xlib.
>
> You have to draw the polygon in non-overlapping pieces, and only those
> pieces that WindingRule would fill. (If you draw it in pieces that
> overlap, that won't necessarily produce the intended result if you use
> GdkGC function values like GDK_INVERT or GDK_XOR that depend on the
> source bits, as the overlapping regions will be painted several
> times.)

Presumably the reason that you got away with using NonConvex
in the older code was simply that the X servers just always
use the same algorithm that works for Complex. Or they 
ignored fill_rule when NonComplex was passed.

Anyways, as long as you only care about X11, then 

 #include <gdkx.h>

 GdkGC *gc;

 gc = gdk_gc_new(); /* Or new_with_values() */
 XSetFillRule (GDK_DISPLAY_XDISPLAY (gc),
               GDK_DISPLAY_XGC (gc),
               WindingRule);

Is probably pretty safe. I won't *guarantee* that will work
with all future GTK+-2.x versions, but I don't see what
would break it.

You might want to file a bug in bugzilla to add the missing
pieces to GdkGC. Considering our current interest in moving
to Cairo (http://www.cairographics.org) as the GDK rendering
API, I'm not sure if we'll bother with a lot of tweaking
of the X API at this point. (And if nobody has complained in 
7 years, it can't be a common need :-), but it can't
hurt.

Regards,
                                Owen