The Actions.xml Catalog

In jEdit as well as in Plugins, actions define procedures that can be bound to a menu item, a toolbar button or a keyboard shortcut. Most plugin Actions [5] are short scripts written in BeanShell, jEdit's macro scripting language. These scripts either direct the action themselves, delegate to a method in one of the plugin's classes that encapsulates the action, or do a little of both. The scripts are usually short; elaborate action protocols are usually contained in compiled code, rather than an interpreted macro script, to speed execution.

Actions are defined by creating an XML file entitled actions.xml and placing it in the plugin JAR file.

The actions.xml file from the QuickNotepad plugin looks as follows:

<ACTIONS>
	<ACTION NAME="quicknotepad.choose-file">
		<CODE>
			wm.addDockableWindow(QuickNotepadPlugin.NAME);
			wm.getDockableWindow(QuickNotepadPlugin.NAME).chooseFile();
		</CODE>
	</ACTION>

	<ACTION NAME="quicknotepad.save-file">
		<CODE>
			wm.addDockableWindow(QuickNotepadPlugin.NAME);
			wm.getDockableWindow(QuickNotepadPlugin.NAME).saveFile();
		</CODE>
	</ACTION>

	<ACTION NAME="quicknotepad.copy-to-buffer">
		<CODE>
			wm.addDockableWindow(QuickNotepadPlugin.NAME);
			wm.getDockableWindow(QuickNotepadPlugin.NAME).copyToBuffer();
		</CODE>
	</ACTION>
</ACTIONS>

Actions in jEdit core

You can see how each action in jEdit core is implemented by inspecting the actions.xml file that is there.

This file defines three actions. They each use a built-in variable wm, which refers to the current view's DockableWindowManager. Whenever you need to obtain a reference to the current dockable, or create a new one, this is the class to use. We use the method addDockable() followed by getDockable() to create if necessary, and then bring up the QuickNotepad plugin dockable. This will be docked or floating, depending on how it was last used.

When an action is invoked, the BeanShell scripts address the plugin through static methods, or if instance data is needed, the current View, its DockableWindowManager, and the plugin object return by the getDockable() method.

If you are unfamiliar with BeanShell code, you may nevertheless notice that the code statements bear a strong resemblance to Java code, with one exception: the variable view is never assigned any value.

For complete answers to this and other BeanShell mysteries, see Part III, “Writing Macros”; two observations will suffice here. First, the variable view is predefined by jEdit's implementation of BeanShell to refer to the current View object. Second, the BeanShell scripting language is based upon Java syntax, but allows variables to be typed at run time, so explicit types for variables need not be declared.

A formal description of each element of the actions.xml file can be found in the documentation of the ActionSet class.



[5] Some plugins, such as Sidekick, Console, and ProjectViewer, create pure Java EditAction-derived Actions, based which services are available, or which files are found in a certain path. However, this is an advanced topic you can explore further in the source and API docs of those plugins.