File Associations and DDE

You can set up file associations in Epsilon for Windows using the create-file-associations command. It lets you modify a list of common extensions, then sets up Windows to invoke Epsilon to edit files with those extensions. The files will be sent to an existing copy of Epsilon, if one is running, via a Windows DDE execute message.

Dynamic Data Exchange, or DDE, is one mechanism in Windows for programs to talk to each other. A DDE server is a program that knows how to "listen" for messages from other programs. A DDE client is a program that knows how to send a message using DDE.

When you double-click on a shell icon, and you want a program to start editing a file, Windows arranges for this in one of two ways. The simple way: Windows just starts a new copy of the program and tells it to edit that file. The disadvantage is that you get multiple copies of the program running, if you click on multiple files.

The better way uses DDE. The create-file-associations command sets things up so that Windows will know how to use DDE to talk to a copy of Epsilon. So now when you double-click on a file registered to Epsilon, Windows will first try to send a message to Epsilon saying "please edit this file". If there's no running copy of Epsilon, Windows will notice that no program accepted the message, and it will know it needs to run the program itself.

Standard bindings:

create-file-associations

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