Core Text APIを使用した際に起こる行間の問題の回避

gistfile1.m

NSFont *normalFont = [NSFont systemFontOfSize:12];
CGRect renderFrame = CGRectMake(0, 0, 300, 50); // box to render the text into

static NSLayoutManager *layMan = nil;
if (!layMan) {
    layMan = [NSLayoutManager new];
}
CGFloat lineHeight = [layMan defaultLineHeightForFont:normalFont]; // calculate the expected height of a line

NSDictionary *attrDict = [NSDictionary dictionaryWithObject:normalFont andKey:NSFontAttributeName];
NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:@"テスト\nテスト\ntest\nテスト" attributes:attrDict];
CTFramesetterRef frameSttr = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrStr);
[attrStr release];
renderFrame = 1000000;
CGPathRef framePath = CGPathCreateMutable();
CGPathAddRect((CGMutablePathRef)framePath, NULL, renderFrame);
CTFrameRef ctFrm = CTFramesetterCreateFrame(frameSttr, CFRangeMake(0, 0), framePath, NULL);
CFRelease(frameSttr);

CGContextRef context = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
CGContextSaveGState(context);
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextScaleCTM(context, 1.0, -1.0); //flip only when this view is flipped

NSArray *lines = (NSArray *)CTFrameGetLines(ctFrm);
CFIndex linesCount = [lines count];

for (NSUInteger i = 0; i < linesCount; i++) {
    // the Y coordinate calculation assumes that the view coordinate system is flipped
    CGContextSetTextPosition(context, renderFrame.origin.x, renderFrame.origin.y + renderFrame.size.height - (lineHeight + 1) * (i + 1));
    CTLineDraw((CTLineRef)[lines objectAtIndex:i], context);
}

CFRelease(ctFrm);

CGContextRestoreGState(context);