Sometimes you might download a ZIP file, then forget about it, and the next time you try to open it up it prompts you for a password, which you've forgotten. Rather than trying to decompress every single ZIP (or RAR, XAR, etc.) file that you download to see if it works without passwords, the File browser (usually, Explorer or Finder) will automatically analyze the file and show a little picture of a key over the ZIP archive file's graphical icon, proactively alerting the user. OSes nowadays analyze files in the background for search indexing purposes already anyway.
-- rhatta, Dec 13 2008

MSDN: Creating Icon Handlers http://msdn.microso...b776857(VS.85).aspx
Microsoft's documentation on how to do this [krelnik, Dec 13 2008]

Windows doesn't do any analysis beyond checking the file extension. This would be fairly easy to implement on other platforms, though.
-- Spacecoyote, Dec 13 2008


Spacecoyote is only partially correct. *By default* Windows only looks at the extension. But the Windows shell supports an extension called an 'icon handler' that can be used to build precisely what you describe here.
-- krelnik, Dec 13 2008


Good plan. I think I may keep that link to MSDN for later - I can already think of a few ways I might use that...
-- dannystaple, Dec 13 2008



random, halfbakery