The EditBus
Prev | Chapter 18. Implementing a Simple Plugin | Next

## The EditBus

Plugins register `EBComponent` instances with the `EditBus` to receive messages reflecting changes in jEdit's state.

The message classes derived from `EBMessage` cover the opening and closing of the application, changes in the status of buffers and views, changes in user settings, as well as changes in the state of other program features. A full list of messages can be found in the org.gjt.sp.jedit.msg package.

`EBComponent`s are added and removed with the `EditBus.addToBus()` and `EditBus.removeFromBus()` methods.

Typically, the `EBComponent.handleMessage()` method is implemented with one or more `if` blocks that test whether the message is an instance of a derived message class in which the component has an interest.

    if(msg instanceof BufferUpdate) {
        // a buffer's state has changed!
    }
    else if(msg instanceof ViewUpdate) {
        // a view's state has changed!
    }
    // ... and so on

If a plugin core class will respond to EditBus messages, it can be derived from `EBPlugin`, in which case no explicit `addToBus()` call is necessary. Otherwise, `EditPlugin` will suffice as a plugin base class. Note that QuickNotepad uses the latter.

Prev | Up | Next
The QuickNotepadPlugin Class | Home | The Property File