QuickTime: Thumb Nails

QuickTime 1.5 and later versions add the ability to see thumb nails of graphics files in the open dialog box of some applications. I have these questions:

* Does the application have to implement this feature?
* What determines whether this feature shows up in a dialog box?
* What are all the file types that QuickTime can generate thumb nails for?

QuickTime includes extensions to the Standard File Package that allow you to create and display file previews -- information that gives the user an idea of a file's contents without opening the file. Typically, a file's preview is a small PICT image (the thumb nail), but previews may also contain other types of information that is appropriate to the type of file. For example, a text file's preview might tell when the file was created and what it discusses.

"Inside Macintosh: QuickTime" has this to say:

"The Movie Toolbox provides two new Standard File functions, StandardGetFilePreview and CustmGetFilePreview, that allow you to display file preview in an open dialog box in System 7 using Standard File reply structures (of type StandardFileReply). The
StandardGetFilePreview function corresponds to the existing StandardGetFile function; the CustomGetFilePreview function corresponds to the existing CustomeGetFile function.

"You use these new functions in place of the existing standard file functions whenever you want to allow the user to display previews during the Open dialog box."

So, whatever you want to display can be previewed based on what the programmer of the application has programmed.