Get a clipping rect for CoreText

gistfile1.m

static CGRect clipRectToPath(CGRect rect, CGPathRef path)
{
    size_t width                = floorf(rect.size.width);
    size_t height               = floorf(rect.size.height);
    uint8_t *points             = calloc(width * height, sizeof(*points));
    CGContextRef bitmapContext  = CGBitmapContextCreate(points, width, height, sizeof(*points) * 8, width, NULL, kCGImageAlphaOnly);
    BOOL atStart                = NO;
    NSRange range               = NSMakeRange(0, 0);
    NSUInteger x                = 0;

    CGContextSetShouldAntialias(bitmapContext, NO);
    CGContextTranslateCTM(bitmapContext, -rect.origin.x, -rect.origin.y);
    CGContextAddPath(bitmapContext, path);
    CGContextFillPath(bitmapContext);
    
    for (; x < width; ++x)
    {
        BOOL isCol = YES;
        for (int i = 0; i < height; ++i)
        {
            if (points[(i * width + x)] < 128)
            {
                isCol = NO;
                break;
            }
        }
        
        if (isCol && !atStart)
        {
            atStart = YES;
            range.location = x;
        }
        else if (!isCol && atStart)
        {
            break;
        }
    }
    
    if (atStart)
        range.length = x - range.location - 1;
    
    CGContextRelease(bitmapContext);
    free(points);
    
    return CGRectMake(rect.origin.x + range.location, rect.origin.y, range.length, rect.size.height);
}