iOS 8 API printing PDFs: broken when drawing text? - objective-c

Question

I have an app that has been happily generating PDFs using quartz/UIKit since iOS 4, but since upgrading the project to iOS 8, crashes whenever it tries to render text into the PDF context. Drawing lines & rectangles is fine, but any permutation of string rendering fails with an exception in one of the low level libraries.
Rather than posting my own source, I tried working backwards from Apple's documentation. Granted it is out of date, but if it's no longer supposed to work, they ought to have fixed it.
https://developer.apple.com/library/ios/documentation/2DDrawing/Conceptual/DrawingPrintingiOS/GeneratingPDF/GeneratingPDF.html
Adapted source code:
- (void)producePDF
{
NSString *text=#"Bzorg blarf gloop foo!";
CFAttributedStringRef currentText = CFAttributedStringCreate(NULL, (CFStringRef)text, NULL);
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(currentText);
NSString *pdfFileName = fullPath;
// Create the PDF context using the default page size of 612 x 792.
UIGraphicsBeginPDFContextToFile(pdfFileName, CGRectZero, nil);
CFRange currentRange = CFRangeMake(0, 0);
NSInteger currentPage = 0;
BOOL done = NO;
do {
// Mark the beginning of a new page.
UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 612, 792), nil);
// Draw a page number at the bottom of each page.
currentPage++;
//[self drawPageNumber:currentPage];
// Render the current page and update the current range to
// point to the beginning of the next page.
//currentRange = [self renderPageWithTextRange:currentRange andFramesetter:framesetter];
currentRange=[self renderPage:currentPage withTextRange:currentRange andFramesetter:framesetter];
// If we're at the end of the text, exit the loop.
if (currentRange.location == CFAttributedStringGetLength((CFAttributedStringRef)currentText))
done = YES;
} while (!done);
// Close the PDF context and write the contents out.
UIGraphicsEndPDFContext();
// Release the framewetter.
CFRelease(framesetter);
// Release the attributed string.
CFRelease(currentText);
}
- (CFRange)renderPage:(NSInteger)pageNum withTextRange:(CFRange)currentRange
andFramesetter:(CTFramesetterRef)framesetter
{
// Get the graphics context.
CGContextRef currentContext = UIGraphicsGetCurrentContext();
// Put the text matrix into a known state. This ensures
// that no old scaling factors are left in place.
CGContextSetTextMatrix(currentContext, CGAffineTransformIdentity);
// Create a path object to enclose the text. Use 72 point
// margins all around the text.
CGRect frameRect = CGRectMake(72, 72, 468, 648);
CGMutablePathRef framePath = CGPathCreateMutable();
CGPathAddRect(framePath, NULL, frameRect);
// Get the frame that will do the rendering.
// The currentRange variable specifies only the starting point. The framesetter
// lays out as much text as will fit into the frame.
CTFrameRef frameRef = CTFramesetterCreateFrame(framesetter, currentRange, framePath, NULL);
CGPathRelease(framePath);
// Core Text draws from the bottom-left corner up, so flip
// the current transform prior to drawing.
CGContextTranslateCTM(currentContext, 0, 792);
CGContextScaleCTM(currentContext, 1.0, -1.0);
// Draw the frame.
CTFrameDraw(frameRef, currentContext);
// Update the current range based on what was drawn.
currentRange = CTFrameGetVisibleStringRange(frameRef);
currentRange.location += currentRange.length;
currentRange.length = 0;
CFRelease(frameRef);
return currentRange;
}
I've tried numerous permutations, and they all seem to fail at the exact point of rendering text. The Apple-derived example above dies at the line:
CTFrameDraw(frameRef, currentContext);
Other code attempts to get the minimum working:
NSMutableParagraphStyle* textStyle = NSMutableParagraphStyle.defaultParagraphStyle.mutableCopy;
textStyle.alignment = NSTextAlignmentLeft;
NSDictionary* textFontAttributes = #{
NSFontAttributeName: [UIFont fontWithName: #"Helvetica" size: 12], NSForegroundColorAttributeName: UIColor.redColor,
NSParagraphStyleAttributeName: textStyle};
[#"Hello, World!" drawAtPoint:CGPointZero withAttributes:textFontAttributes];
... crashes at the "drawAtPoint" call.

Answer 1

For what it's worth, if I execute the app on a device without the debugger attached (i.e. run/kill/launch from springboard), the PDF creation works just fine. Presumably whatever bogus exception was getting thrown just gets ignored in real life.