Why does QLPreviewRequestSetDataRepresentation on Mavericks return error " CGImageCreate: invalid image size: 0 x 0" for png

Question

My quick look generator used to work properly but is now broken.
Is it a bug or am I doing something wrong?

Here’s my code:

OSStatus GeneratePreviewForURL(void *thisInterface, QLPreviewRequestRef preview, 
                               CFURLRef url, CFStringRef contentTypeUTI, 
                               CFDictionaryRef options) {

    NSDictionary * myDoc = [NSDictionary dictionaryWithContentsOfURL:(NSURL *)url];

        if (myDoc) {

            NSData * pngData = [myDoc valueForKey:@"pngPreview"];

            if (pngData) {

                QLPreviewRequestSetDataRepresentation(preview,(__bridge CFDataRef)pngData,
                                                      kUTTypeImage,NULL);
            }
        }
}

My doc is a normal plist with a png preview stored as data in it.
I checked that pngPreview does contain png data, I created the image and its size was 350×350.

However, I’m constantly getting these errors:

qlmanage[702] : CGImageCreate: invalid image size: 0 x 0.

qlmanage[702:303] *** CFMessagePort: bootstrap_register(): failed 1100 (0x44c) 'Permission denied', port = 0x9e27, name = 'com.apple.tsm.portname'
See /usr/include/servers/bootstrap_defs.h for the error codes.

qlmanage[702:303] *** CFMessagePort: bootstrap_register(): failed 1100 (0x44c) 'Permission denied', port = 0x3f2b, name = 'com.apple.CFPasteboardClient'
See /usr/include/servers/bootstrap_defs.h for the error codes.

    qlmanage[702:303] Failed to allocate communication port for com.apple.CFPasteboardClient; this is likely due to sandbox restrictions

My app is not sandboxed so I don’t think the last 3 errors are important.

I used to use kUTTypePNG but have tried kUTTypeImage to no avail (the docs for QLPreviewRequestSetDataRepresentation says currently supported UTIs are kUTTypeImage, kUTTypePDF, kUTTypeHTML, kUTTypeXML, kUTTypePlainText, kUTTypeRTF, kUTTypeMovie, and kUTTypeAudio).

Other points to consider: The docs state: "The binary of a Quick Look generator must be universal and must be 32-bit only." This page But this page states: "For OS X v10.6 and later, you must build Quick Look generators for both 32- and 64-bit." Which is rather unclear...
How do I set my target?

If it used to work then it's a bug. Binary compatibility is important. Have you filed a bug at bugreport.apple.com? — Thomas Deniau
Thanks, I'll do it and tell them to update the docs too: all is given for the old Xcode, especially the how to debug docs are misleading. — wdyp
@wdyp If you can, please post on OpenRadar so others can track the bug! — Wil Gieseler

Guy Moreillon Guy Moreillon · Accepted Answer · 2014-10-07T19:09:01

Facing the same problem I've decided to go an alternate route: use QLPreviewRequestCreateContext to get a context in which to draw my image in:

QLPreviewRequestRef preview; // The preview request passed to GeneratePreviewForURL()
CGImageRef image;  // Create your CGImage however you like
CGSize size = CGSizeMake(CGImageGetWidth(image), CGImageGetHeight(image));
CGContextRef ctxt = QLPreviewRequestCreateContext(preview, size, YES, nil);
CGContextDrawImage(ctxt, CGRectMake(0, 0, size.width, size.height), image);
QLPreviewRequestFlushContext(preview, ctxt);
CGContextRelease(ctxt);

At least that works...

Why does QLPreviewRequestSetDataRepresentation on Mavericks return error " CGImageCreate: invalid image size: 0 x 0" for png

1 Answers