bigears. Drawing rotated and positioned text within a path using CoreText (OS X command line, intended to be bug report for apple but highlighted a bug of mine)

main.m

//
//  main.m
//  bigears
//
//  Created by Kevin Meaney on 18/02/2015.
//  Copyright (c) 2015 Kevin Meaney. All rights reserved.
//

#import <Foundation/Foundation.h>

const size_t context_width = 400;
const size_t context_height = 400;

const CGFloat textBoxHeight = 22.0;
const CGFloat textBoxWidth = 124.0;

const CGRect textBoundingBox = { { -textBoxWidth * 0.5, -textBoxHeight * 0.5 },
                                    { textBoxWidth, textBoxHeight } };

NSString *GetFolderPath()
{
    NSString *fp = [@"~/Desktop/RotatedText/" stringByExpandingTildeInPath];
    return fp;
}

void MakeDestinationFolder()
{
    NSString *fp = GetFolderPath();
    NSFileManager *fm = [NSFileManager defaultManager];
    if (![fm fileExistsAtPath:fp])
    {
        [fm createDirectoryAtPath:fp
      withIntermediateDirectories:YES
                       attributes:NULL
                            error:NULL];
    }
}

void SaveCGImageToAPNGFile(CGImageRef theImage, NSString *fileName)
{
    NSString *fp = GetFolderPath();
    NSString *destination = [NSString stringWithFormat:@"%@/%@",
                             [fp stringByExpandingTildeInPath], fileName];
    
    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:destination];
    CGImageDestinationRef exporter = CGImageDestinationCreateWithURL(
                                                     (__bridge CFURLRef)fileURL,
                                                     kUTTypePNG, 1, NULL);
    CGImageDestinationAddImage(exporter, theImage, nil);
    CGImageDestinationFinalize(exporter);
    CFRelease(exporter);
}

void SaveCGBitmapContextToAPNGFile(CGContextRef context, NSString *fileName)
{
    CGImageRef image = CGBitmapContextCreateImage(context);
    SaveCGImageToAPNGFile(image, fileName);
    CGImageRelease(image);
}

CGContextRef CreateBitmapContext()
{
    CGColorSpaceRef space = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
    CGContextRef context = CGBitmapContextCreate(nil, context_width,
                                context_height, 8, context_width * 4, space,
                                (CGBitmapInfo)kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(space);
    return context;
}

void FillRectInContextWithColour(CGContextRef context, CGRect rect,
                                 CGColorRef colour)
{
    CGContextSaveGState(context);
    CGContextSetFillColorWithColor(context, colour);
    CGContextFillRect(context, rect);
    CGContextRestoreGState(context);
}

void FillPathInContextWithColour(CGContextRef context, CGPathRef path,
                                  CGColorRef colour)
{
    CGContextSaveGState(context);
    CGContextAddPath(context, path);
    CGContextSetFillColorWithColor(context, colour);
    CGContextFillPath(context);
    CGContextRestoreGState(context);
}

void ClearContext(CGContextRef context)
{
    CGColorRef colour = CGColorCreateGenericRGB(1.0, 1.0, 1.0, 1.0);
    CGRect contextRect = CGRectMake(0.0, 0.0, context_width, context_height);
    FillRectInContextWithColour(context, contextRect, colour);
    CGColorRelease(colour);
}

CGPathRef CreateTextRoundedBoundingBoxPath()
{
    CGFloat cornderRadius = 8.0;
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, textBoundingBox.origin.x + cornderRadius,
                      textBoundingBox.origin.y);
    
    CGPoint arcCentre;
    arcCentre = CGPointMake(
            textBoundingBox.origin.x + textBoundingBox.size.width - cornderRadius,
            textBoundingBox.origin.y + cornderRadius);
    CGPathAddArc(path, NULL, arcCentre.x, arcCentre.y,
                 cornderRadius, -M_PI_2, 0.0, 0);
    
    arcCentre = CGPointMake(
            textBoundingBox.origin.x + textBoundingBox.size.width - cornderRadius,
            textBoundingBox.origin.y + textBoundingBox.size.height - cornderRadius);
    CGPathAddArc(path, NULL, arcCentre.x, arcCentre.y, cornderRadius, 0.0, M_PI_2, 0);
    
    arcCentre = CGPointMake(textBoundingBox.origin.x + cornderRadius,
            textBoundingBox.origin.y + textBoundingBox.size.height - cornderRadius);
    CGPathAddArc(path, NULL, arcCentre.x, arcCentre.y,
                 cornderRadius, M_PI_2, M_PI, 0);
    
    arcCentre = CGPointMake(textBoundingBox.origin.x + cornderRadius,
                            textBoundingBox.origin.y + cornderRadius);

    CGPathAddArc(path, NULL, arcCentre.x, arcCentre.y, cornderRadius,
                 M_PI, M_PI + M_PI_2, 0);
    CGPathRef newPath = CGPathCreateCopy(path);
    CGPathRelease(path);
    return newPath;
    // return CGPathCreateWithRoundedRect(textBoundingBox, 12, cornderRadius, NULL);
}

CFDictionaryRef CreateTextAttributesDictionary()
{
    const CGFloat fontSize = 16.0;
    CFStringRef postscriptFontName = CFSTR("Avenir-Black");
    CTTextAlignment alignment = kCTTextAlignmentCenter;

    // CGColorRef textColour = CGColorCreateGenericRGB(0.0, 0.0, 0.0, 0.8);
    CGFloat colour[4];
    colour[0] = 0.0;
    colour[1] = 0.1;
    colour[2] = 0.1;
    colour[3] = 0.8;
    CGColorSpaceRef profile = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
    CGColorRef textColour = CGColorCreate(profile, colour);
    CTFontRef theFont = CTFontCreateWithName(postscriptFontName, fontSize, NULL);
    // CTFontRef theFont = CTFontCreateWithName((__bridge CFStringRef)@"Avenir-Black", fontSize, NULL);

    CFMutableDictionaryRef mutDict = CFDictionaryCreateMutable(kCFAllocatorDefault,
        0, &kCFCopyStringDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    CFDictionaryAddValue(mutDict, kCTFontAttributeName, theFont);
    CFDictionaryAddValue(mutDict, kCTForegroundColorAttributeName, textColour);
    CTParagraphStyleSetting settings[] = {
        {   kCTParagraphStyleSpecifierAlignment,
            sizeof(alignment),
            &alignment} };
    CTParagraphStyleRef paragraphStyle = NULL;
    paragraphStyle = CTParagraphStyleCreate(settings,
                                            sizeof(settings) / sizeof(settings[0]));
    CFDictionaryAddValue(mutDict, kCTParagraphStyleAttributeName, paragraphStyle);
    CFRelease(profile);
    CFRelease(theFont);
    CGColorRelease(textColour);
    CFRelease(paragraphStyle);
    CFDictionaryRef dict = CFDictionaryCreateCopy(kCFAllocatorDefault, mutDict);
    CFRelease(mutDict);
    return dict;
}

CFAttributedStringRef CreateTextAttributedString()
{
    CFDictionaryRef textAttribs = CreateTextAttributesDictionary();
    CFStringRef textToDraw = CFSTR("Going around");
    CFAttributedStringRef attribString = CFAttributedStringCreate(
                                kCFAllocatorDefault, textToDraw, textAttribs);
    CFRelease(textAttribs);
    return attribString;
}

void RotateAndTranslateContext(CGContextRef context, CGFloat angle,
                               CGFloat translation)
{
    // CGContextTranslateCTM(context, context_width * 0.5, context_height * 0.5);
    CGContextTranslateCTM(context, 100 + translation, 100 + translation);
    CGContextRotateCTM(context, angle);
}

void FillPathRectAndDrawStringInContext(CGContextRef context, CGPathRef path,
                                CFAttributedStringRef attribString)
{
    // CGRect boundingBox = CGPathGetBoundingBox(path);
    CGColorRef boxColour = CGColorCreateGenericRGB(0.7, 0.8, 0.9, 1.0);
    FillPathInContextWithColour(context, path, boxColour);
    CTFramesetterRef frameSetter;
    frameSetter = CTFramesetterCreateWithAttributedString(attribString);
    CTFrameRef theFrame = CTFramesetterCreateFrame(frameSetter,
                        CFRangeMake(0, CFAttributedStringGetLength(attribString)),
                                                   path, NULL);
    CFRelease(frameSetter);
    CTFrameDraw(theFrame, context);
    CFRelease(theFrame);
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        MakeDestinationFolder();
        CGPathRef textPath = CreateTextRoundedBoundingBoxPath();
        CGContextRef bitmap = CreateBitmapContext();
        CFAttributedStringRef attribString = CreateTextAttributedString();
        const int numImages = 60;
        CGFloat angle;
        CGFloat translation;
        // CGFloat startAngle = -M_PI;
        CGFloat diff = M_PI * 2.0 / (numImages - 1);
        for (int i = 0 ; i < numImages ; ++i)
        {
            ClearContext(bitmap);
            CGContextSaveGState(bitmap);
            // angle = startAngle + i * diff;
            angle = i * diff;
            translation = i * 200 / (numImages - 1);
            RotateAndTranslateContext(bitmap, angle, translation);
            FillPathRectAndDrawStringInContext(bitmap, textPath, attribString);
            CGContextRestoreGState(bitmap);
            NSString *fN;
            fN = [[NSString alloc] initWithFormat:@"RotatedText%03d.png", i];
            SaveCGBitmapContextToAPNGFile(bitmap, fN);
        }
        CGPathRelease(textPath);
        CGContextRelease(bitmap);
        CFRelease(attribString);
    }
    return 0;
}