Can I write a QuickLook generator for folders in OS X 10.9

Question

I'm playing with QuickLook generators in OS X and it looks like you can't "override" the default preview for folders, although you probably could until you upgraded to SnowLeopard.

I tested it with my simple QuickLook generator using qlmanage and it's really disabled:

> qlmanage -d -g /Users/martin/Library/QuickLook/quicklooktest.qlgenerator -c public.folder -p /Users/martin/Library/QuickLook/

Testing Quick Look preview with files:
    /Users/martin/Library/QuickLook/quicklooktest.qlgenerator
    /Users/martin/Library/QuickLook/
    - force using content type UTI: public.folder
[ERROR] Can't get plugin bundle info at file:///Applications/Contents/Library/QuickLook/QuickLookPlugin.qlgenerator/
[WARNING] Generators for folders are forbidden - ignoring <QLGenerator /Users/martin/Library/QuickLook/quicklooktest.qlgenerator>
2014-01-03 13:00:46.308 qlmanage[8687:507] *** CFMessagePort: bootstrap_register(): failed 1100 (0x44c) 'Permission denied', port = 0x9523, name = 'com.apple.tsm.portname'
See /usr/include/servers/bootstrap_defs.h for the error codes.
2014-01-03 13:00:46.308 qlmanage[8687:507] *** CFMessagePort: bootstrap_register(): failed 1100 (0x44c) 'Permission denied', port = 0x3f4b, name = 'com.apple.CFPasteboardClient'
See /usr/include/servers/bootstrap_defs.h for the error codes.
2014-01-03 13:00:46.309 qlmanage[8687:507] Failed to allocate communication port for com.apple.CFPasteboardClient; this is likely due to sandbox restrictions
[WARNING] Generators for folders are forbidden - ignoring <QLGenerator /Users/martin/Library/QuickLook/quicklooktest.qlgenerator>

It says [WARNING] Generators for folders are forbidden. Is this permanent? Can I allow it somehow?

Answer 1

Sorry, but it's been impossible to provide generators for folders since Snow Leopard indeed. You should file a bug with Apple is this is a feature you need, but I wouldn't keep my hopes up.