I have the following method in a category on NSBezierPath, which seems to be
what you want, and works in the same way as -addClip:
- (void) addInverseClip
// this is similar to -addClip, except that it excludes the area
bounded by the path instead of includes it. It works by combining this path
// with the existing clip area using the E/O winding rule, then setting
the result as the clip area. This should be called between
// calls to save and restore the gstate, as for addClip.
CGContextRef context = [[NSGraphicsContext currentContext]
graphicsPort];
CGRect cbbox = CGContextGetClipBoundingBox( context );
NSBezierPath* cp = [NSBezierPath bezierPathWithRect:*(NSRect*)&cbbox];
[cp appendBezierPath:self];
[cp setWindingRule:NSEvenOddWindingRule];
[cp addClip];
}
--Graham
On 30/10/2012, at 12:22 AM, Roland King <r...@rols.org> wrote:
> I have a graphics context and a path and I want to clip everything inside the
> path, ie not display it, and leave everything outside the path displayed. The
> path is simple and doesn't cross itself, for sake of example it may as well
> be a circle. If I start with a clip-free GC and set that circle as a clipping
> path, I'll get the opposite, everything in the circle will show, how do I do
> the other way around? Does it work if I set a path at the bound rect of the
> GC plus my shape in the middle? That would seem to have two crossings to get
> into the shape, one at the bounds of the rect, one as you cross the shape,
> which should mean everything inside the shape is 'outside' but does a path at
> the very extremities of the GC, or even outside it, count as 'crossed'?
>
> The more I think about it, the more clipping sounds hard to implement
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