Understudy provides a means to customize the way the System 7.0 Finder opens documents. You may have noticed that the Finder (by default) will offer to open a TEXT or PICT document with TeachText, if the application that originally created the document is unavailable. This mechanism is controlled by a resource in the Finder itself, so it is extensible. Understudy provides a semi-convenient way to modify this behavior, without changing the Finder.
The System 7.0 Finder also allows you to drop documents on top of applications if the application contains a resource "accepting" the document type. Understudy also allows you to customize this behavior without modifying your applications to add new document types.
Installation
You should place the Understudy file in the Extensions folder of your System Folder, and the Understudy Preferences file in the Preferences folder. (System 7.0 will automatically install Understudy if you drop it onto the System Folder icon.)
Configuration
Currently, to configure Understudy, you need to use ResEdit. Open the Understudy Preferences file with ResEdit and open the resource with type='2Map' and ID=0. You should see a list of entries.
Each entry contains a document type and an application signature. This information tells the Finder that documents of the specified type can be opened by the specified application if the creating application is unavailable. The list contained in Understudy is inserted before the Finder's normal list, and can override the Finder's use of TeachText, for example.
Next, open the resource with type='2Map' and ID=1. This contains the same kind of list of entries. In this case, however, the list specifies additional document types that can be dropped onto the designated application. I made these lists separate for flexibility, but often they will be the same.
By default, Understudy Preferences is set up so that MacWrite 5.x, Microsoft Word, and WriteNow files can be opened by and dropped onto MacWrite II. (MacWrite II can handle all these file types, using the Claris XTND architecture.) You can change these lists as much as you'd like.
Caveats
This is an early release of Understudy, so it is very preliminary, and has no user interface. But, I've been using it for a few weeks now without problems. Let me know if you have comments or problems.
