TextRendering CoreText

TextRendering.m

- (void)drawRect:(NSRect)dirtyRect {
    [super drawRect:dirtyRect];
    
    CGContextRef ctx = [NSGraphicsContext currentContext].CGContext;
    [NSColor.blackColor setFill];
    CGContextFillRect(ctx, CGRectMake(0, self.label.frame.size.height, self.label.frame.size.width, self.label.frame.size.height));
    
    CFIndex stringLen = CFStringGetLength(text);
    CTFontRef font = CTFontCreateUIFontForLanguage(kCTFontUIFontSystem, 24.0f, nil);

    // MARK: - Get Glyph Rects
    UniChar *characters = (UniChar *)malloc(sizeof(UniChar) * stringLen);
    CGGlyph *glyphs = (CGGlyph *)malloc(sizeof(CGGlyph) * stringLen);
    CGRect *glyphRects = (CGRect *)malloc(sizeof(CGRect) * stringLen);
    
    CFStringGetCharacters(text, CFRangeMake(0, stringLen), characters);
    CTFontGetGlyphsForCharacters(font, characters, glyphs, stringLen);
    CTFontGetBoundingRectsForGlyphs(font, kCTFontOrientationDefault, glyphs, glyphRects, stringLen);
    
    // MARK: - Draw Glyph Rects
    CFMutableAttributedStringRef attributedString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
    CFAttributedStringReplaceString(attributedString, CFRangeMake(0, 0), text);
    CFAttributedStringSetAttribute(attributedString, CFRangeMake(0, CFAttributedStringGetLength(attributedString)), kCTFontAttributeName, font);
    
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attributedString);
    
    CFRange fitRange;
    CGSize frameSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0, 0), NULL, CGSizeMake(self.bounds.size.width, CGFLOAT_MAX), &fitRange);
    
    [NSColor.redColor setStroke];
    CGContextTranslateCTM(ctx, 0, self.label.frame.size.height);
    CGContextStrokeRect(ctx, CGRectMake(0, 0, frameSize.width, frameSize.height));
    
    CTTypesetterRef typesetter = CTTypesetterCreateWithAttributedString(attributedString);
    CTLineRef line = CTTypesetterCreateLine(typesetter, CFRangeMake(0, stringLen));
    CFArrayRef runs = CTLineGetGlyphRuns(line);
    
    [NSColor.greenColor setStroke];
    [NSColor.labelColor setFill];
    for (int i = 0; i < CFArrayGetCount(runs); i++) {
        CTRunRef run = CFArrayGetValueAtIndex(runs, i);
        
        CFIndex glyphCount = CTRunGetGlyphCount(run);
        
        CGGlyph *glyphs = malloc(sizeof(CGGlyph) * glyphCount);
        CTRunGetGlyphs(run, CFRangeMake(0, 0), glyphs);
        
        CGPoint *glyphPositions = malloc(sizeof(CGSize) * glyphCount);
        CTRunGetPositions(run, CFRangeMake(0, 0), glyphPositions);
        
        CGRect *glyphRects = malloc(sizeof(CGRect) * glyphCount);
        CTFontGetBoundingRectsForGlyphs(font, kCTFontOrientationDefault, glyphs, glyphRects, glyphCount);
        
        for (int j = 0; j < glyphCount; j++) {
            CGRect rect = CGRectOffset(glyphRects[j], glyphPositions[j].x, glyphPositions[j].y);
            rect = CGRectApplyAffineTransform(rect, CGAffineTransformMakeScale(1, -1));
            rect = CGRectOffset(rect, 0, frameSize.height);
            CGContextStrokeRect(ctx, rect);
            
            CGAffineTransform glyphTransform = CGAffineTransformMakeTranslation(glyphPositions[j].x, glyphPositions[j].y + frameSize.height);
            
            glyphTransform = CGAffineTransformScale(glyphTransform, 1, -1);

            CGPathRef glyphPath = CTFontCreatePathForGlyph(font, glyphs[j], &glyphTransform);
            CGContextSaveGState(ctx);
//            CGContextTranslateCTM(ctx, rect.origin.x, rect.origin.y);
//            CGContextScaleCTM(ctx, 1, -1);
            CGContextAddPath(ctx, glyphPath);
            CGContextFillPath(ctx);
            CGContextRestoreGState(ctx);
            
            CGPathRelease(glyphPath);
        }
        
        free(glyphRects);
        free(glyphPositions);
        free(glyphs);
    }
    
    CFRelease(line);
    CFRelease(typesetter);
    CFRelease(framesetter);
    CFRelease(attributedString);
    free(characters);
    free(glyphs);
    CFRelease(font);
}