从NSBezierPath中切出一个矩形

// Save the current clipping region
[NSGraphicsContext saveGraphicsState];
NSRect dontDrawThisRect = NSMakeRect(x, y, w, h);
// Either:
NSRectClip(dontDrawThisRect);
// Or (usually for more complex shapes):
//[[NSBezierPath bezierPathWithRect:dontDrawThisRect] addClip];
[myBezierPath fill];    // or stroke, or whatever you do
// Restore the clipping region for further drawing
[NSGraphicsContext restoreGraphicsState];

NSBezierPath *circlePath = [NSBezierPath bezierPathWithOvalInRect:NSMakeRect(0, 0, 100, 100)];
NSBezierPath *rectPath = [NSBezierPath bezierPathWithRect:NSMakeRect(25, 25, 50, 50)];
rectPath = [rectPath bezierPathByReversingPath];
[circlePath appendBezierPath:rectPath];