David Smith wrote: > I believe it's as simple as having your file type > registered with the OS (so it knows what application > to use). If it's an image then associate it a suitable > image editor and see what happens.
No, it's not that simple. Ever seen a preview of a Pascal file? It's registered to be opened by Delphi. The OS doesn't automtically "know" a file is an image file, and merely associating an image editor with it wouldn't help: How does the OS know the program is an image editor? How does the OS know how to operate that program? Does the editor support the image format that the OS expects its thumbnail to be in? You need to tell the shell how to get a thumbnail image from the file's contents. That involves registering an shell extension that implements IExtractImage. It should also implement IPersist and IPersistFile. You can try using Jim Kueneman's EasyNSE suite to help you build the shell extension in Delphi. In Windows Vista, you can register an IThumbnailProvider implementer along with companion interfaces IInitializeWithStream, IInitializeWithItem, and IInitializeWithFile. -- Rob
