Generating a PDF using the new printing stuff in iOS 4.2

Question

Historically, my app has generated confirmations as plain HTML and passed that HTML to the normal MFMailComposeViewController for emailing to the customer. I wanted to try to leverage the new printing classes in iOS 4.2 to render the HTML to a PDF instead and send that as an attachment.

I tried the following:

NSString *html = /* generate my HTML here */
NSMutableData *pdfData = [NSMutableData data];
UIMarkupTextPrintFormatter *fmt = [[UIMarkupTextPrintFormatter alloc] 
                                   initWithMarkupText:html];

// Render the html into a PDF
UIGraphicsBeginPDFContextToData( pdfData, CGRectZero, nil );

for (NSInteger i=0; i < [fmt pageCount]; i++)
{
    UIGraphicsBeginPDFPage();
    CGRect bounds = UIGraphicsGetPDFContextBounds();
    [fmt drawInRect:bounds forPageAtIndex:i];
}

UIGraphicsEndPDFContext();

The problem is that [fmt pageCount] always returns zero, so no actual page content is ever rendered into the PDF NSData.

Has anyone had any luck using UIMarkupTextPrintFormatter outside of an actual print job to convert HTML to PDF? Any help much appreciated.

Answer 1

It seems as though print formatters (including UIMarkupTextPrintFormatter) aren't actually rendered/drawn until right before printing, once the system takes over and starts the print job. (Apple's docs say drawRect: is called right before printing to provide the content for the print job.)

Someone please prove me wrong because I need to do basically the same thing :)

Answer 2

I do this in one of my apps. See my answer to a similar question, here:

Is there any way to generate PDF file from a XML/HTML template in iOs

Answer 3

I made a discovery: this is possible, if you're willing or allowed to use private API. (e.g., in an enterprise app.)

The method: create your formatter as usual; install it in a UIPrintPageRenderer.

Set the renderer's private properties paperRect and printableRect appropriately.

numberOfPages now works!

Set up your pdf cgcontext like normal, and draw the page with the renderer's drawPageAtIndex:inRect: method. Holy cow, it worked.

Obligatory protestation: yes, I know Apple doesn't want you submitting apps that call (e.g.) [ppr setValue:[NSValue valueWithCGRect:page] forKey:@"paperRect"]; and will bounce them.