On Aug 27, 2009, at 04:34, Graham Cox wrote:
I'm using the following code to generate thumbnail images in one of
my user interfaces. It works fine on my machine, and on all the ones
I've tested, but a couple of users have reported that they don't see
the thumbnails. One user experiencing this problem helped me to log
some results which shows that the QLThumbnailImageCreate function is
returning nil. The docs state that this will return nil if it can't
read the file, but it's the exact same file on every system, loaded
from my app's resources. So why would it fail in a few percent of
cases, but mostly work? All affected users are running the latest
system version.
CFURLRef url = CFURLCreateWithFileSystemPath( NULL, (CFStringRef)
[self path], kCFURLPOSIXPathStyle, NO );
// logging the URL/path at this point shows that the correct path
is being returned from [self path], a path to app internal resources
CGSize maxImageSize = CGSizeMake( 512, 512 );
NSDictionary* options = [NSDictionary dictionaryWithObjectsAndKeys:
(id)kCFBooleanTrue, kQLThumbnailOptionIconModeKey, nil];
CGImageRef qli = QLThumbnailImageCreate( NULL, url, maxImageSize,
(CFDictionaryRef)options );
CFRelease( url );
// on a very few systems, qli is nil here
a. It would be worth trying to read the file directly, before calling
QLThumbnailImageCreate, to find out if the problem is the reference to
the file or the image creation.
b. What file system is being used on the Macs where it fails? I don't
know much about such things, but it seems at least theoretically
possible that there might be a capabilities mismatch between the file
system and QL.
FWIW
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