Editor specific command state

Question

I have created a command and a handler that interacts with text editors (objects implementing ITextEditor). For each editor that the handler interacts with I'd like to store some data that the handler has access to.

What is the best way to do this?

Information about my specific problem

My command modifies the selection of text of the active editor. When the command is executed I want to store information about the previous selection. Another command should be able read this information and restore the previous selection.

Thoughts and observations

• If one handler instance was created for each editor that would solve my problem. Is there a way to achieve this?
• I've looked at the source code of the Java editor, trying to understand how things work there. The editor stores references to action objects. Since I can't create new fields for my command I can't use the same approach.
• I've looked at the <state> plugin.xml tag, but I don't understand how to get one piece of state for each editor. But maybe there is a way?
• I could manually maintain a map from editor to state object, and maybe register a listener for when editors are opened and closed. But I would prefer if there was a simpler way, where I didn't have to do this myself.
• Maybe actions (IAction) could be used? But aren't they an old mechanism that has been substituted by commands?
• I could maybe manually set an IAction object which as an reference to the stack using the ITextEditor.setAction.

Answer 1

If you are using Eclipse 4 you could use the transient data of the MPart object associated with the IEditorPart.

To get the MPart from an IEditorPart use:

MPart part = editor.getSite().getService(MPart.class);

Map<String, Object> transientData = part.getTransientData();

You can store anything you like in the transient data, use a key unique to your handler for the map key. The data is discarded when the editor closes.