Why does the worm Helvetica Neue Bold draw like an ordinary subpath in NSBezierPath?

Question

I want to take a filled rectangle and punch a hole in it using a different shape. This is exactly the thing NSBezierPath . You add a rectangular path, then add a sub-item that “punches” it and finally fills it. In my case, the subpath is actually text. No problem, it works fine:

Except when I use Helvetica Neue Bold for my font. When I use this, I just get a solid blue rectangle without any text. But the subpath is really drawn - in fact, if I cut the filled rectangle a bit, you can see some text path:

I get the same behavior with Helvetica Neue Italic. Helvetica Neue Medium works great, like Helvetica Bold, Times New Roman Bold and Arial Bold.

I tried using both NSEvenOddWindingRule and NSNonZeroWindingRule . ( EDIT : Apparently, I really did not try to use the NSEvenOddWinding rule, because it works anyway)

This is the code that I use inside the drawRect method of my NSView subclass.

 NSLayoutManager *layoutManger = [[[NSLayoutManager alloc] init] autorelease]; NSTextContainer *textContainer = [[[NSTextContainer alloc] initWithContainerSize:NSMakeSize(300, 100)] autorelease]; NSFont *font = [NSFont fontWithName:@"Helvetica Neue Bold" size:100]; NSDictionary *textAttribs = [NSDictionary dictionaryWithObjectsAndKeys: font, NSFontAttributeName, nil]; NSTextStorage *textStorage = [[[NSTextStorage alloc] initWithString:@"Hello" attributes:textAttribs] autorelease]; [layoutManger addTextContainer:textContainer]; [layoutManger setTextStorage:textStorage]; NSRange glyphRange = [layoutManger glyphRangeForTextContainer:textContainer]; NSGlyph glyphArray[glyphRange.length]; NSUInteger glyphCount = [layoutManger getGlyphs:glyphArray range:glyphRange]; NSBezierPath *path = [NSBezierPath bezierPathWithRect:NSMakeRect(0, 0, 200, 100)]; [path appendBezierPathWithGlyphs:glyphArray count:glyphCount inFont:font]; [[NSColor blueColor] setFill]; [path fill]; 

So what is going on here? Why do some fonts behave differently than others when it comes to adding glyphs to a path?

EDIT . The solution is to use an NSEvenOddWindingRule . After creating the path add this line:

 [path setWindingRule:NSEvenOddWindingRule]; 

Peter Hawsey's answer provides an explanation of why this is so.

Answer 1

This is probably due to the paths in the fonts. A single font can use clockwise paths; another can use the paths counterclockwise.

A more reliable way to achieve the effect you are doing would be to simply fill out the rectangle and then extract the text from it with the graphic context layout mode set to NSCompositeSourceOut . You can wrap the fill and draw text on a transparent layer with Core Graphics if you want to cut text from the fill only.