Default Application is a utility for configuring Finder 7ﾕs choice of the application to launch for documents whose creators canﾕt be found. For example, I have my Finder configured so that if I double-click a MacWrite II or Microsoft Word document, it is automatically opened with MacWrite Pro. There are other utilities around for doing this, but what make mine different is that itﾕs a control panel, and lets you make changes quickly, without quitting and restarting the Finder.
Installing Default Application is easy; simply put it anywhere itﾕs convenient to you. Control panels normally go in the ﾒControl Panelsﾓ folder, but this is really only a requirement for those control panels that load code into the system at startup (such as Appleﾕs Easy Access). Default Application does no such thing, so it can go anywhere.
Theory of operation: every Macintosh file has a four-character type code, which is supposed to be an indicator of the type of content of the file: for example, plain text files have type ﾒTEXTﾓ, QuickDraw pictures are stored in files of type ﾒPICTﾓ, and so on. Files also have a four-character signature code; the Finder uses this to identify the application to be launched when you double-click a document. For example, the MacWrite Pro application and its documents all have the signature ﾒMWPRﾓ.
However, you might occasionally receive documents from other people, which were created with applications you donﾕt have. Finder 7 has built into it a list of default applications to use to open these documents. The standard list allows you, among other things, to open ﾒTEXTﾓ and ﾒPICTﾓ documents with Appleﾕs TeachText utility, but this list can be extended to include any other document types that you may need to handle. Each entry in the list contains a document type, and the signature of the default application to launch. Of course, itﾕs up to you to ensure that the application can in fact handle documents of that type.
I wonﾕt go into step-by-step detail of how to use Default Application; if you need detailed help, simply turn on System 7ﾕs Balloon Help.
Small usage note: you might like to be able to specify more than one application to use to open documents of a certain type; if the first application canﾕt be found, the Finder should look for the second one, and so on. This doesnﾕt work. If you have two entries specifying the same document type, the Finder only looks at the first one.
･Compatibility caveat: the Finderﾕs default application information is not officially documented, and its format could change in some future version of the Finder. If that should happen, Default Application could malfunction in all kinds of mysterious ways, and in the worst case could corrupt the Finder. Use at your own risk!･
Have fun. Please let me know if you hit any problems. Suggestions for improvement are welcome.
ﾆ Development history:
1.0d3 1992 March 28
First public release.
1.0d4 1992 May 25
Made sure add/modify dialog is always fully on-screen, regardless of position of main control panel window ﾑ otherwise OK/Cancel buttons could become inaccessible.
1.0d5 1992 July 1
Donﾕt try locking a nonexistent handle on the initialization call. Hopefully this should fix those crashes some people have been reporting. Serves me right for not reading the documentation more closely...
1.0a1 1994 January 31
Update for newer Finders which lock their resource map against changes. I bring up a notification dialog with the option to override the lock. Also put in a bit more error checking.
