Truncate a string, with an ellipsis in the center, to a max point width, without splitting composed character sequences (grapheme clusters).

NSString+MaxWidth.m

- (NSString *)stringByInsertingCenterEllipsisWithMaxWidth:(CGFloat)maxWidth font:(NSFont *)font {
	NSDictionary *attrs = @{ NSFontAttributeName: font };
	NSSize size = [self sizeWithAttributes:attrs];

	if (size.width <= maxWidth)
		return self;

	NSMutableString *mutable = [self mutableCopy];
	NSMutableString *mutableWithEllipsis = nil;

	while (size.width > maxWidth) {
		NSUInteger length = [mutable length];
		NSUInteger middleIndex = length / 2;

		NSRange composedCharacterRange = [mutable rangeOfComposedCharacterSequenceAtIndex:middleIndex];

		mutableWithEllipsis = [mutable mutableCopy];

		[mutableWithEllipsis replaceCharactersInRange:composedCharacterRange withString:@"…"];
		[mutable replaceCharactersInRange:composedCharacterRange withString:@""];

		size = [mutableWithEllipsis sizeWithAttributes:attrs];
	}

	return mutableWithEllipsis;
}

Feels kind of dirty/inefficient.

I use this for menu item title truncation, so font will often be [NSFont menuFontOfSize:14.0].

Probably better if it was on NSAttributedString instead?

Actually, that's slower. Using a layout manager might help immensely, though.