How is eclipse line number status line contribution item implemented?

Question

I need to update status line editor-specific information. I already have my own implementation, but I would like to take a look how is eclipse contribution item, which shows

Answer 1

I'm not exactly sure what you are asking for, but there is a concrete implementation of IStatusLineManager here: org.eclipse.jface.action.StatusLineManager

Typically, if you want to access the status line and you have a handle for an editor, you can do something like this (borrowed from org.eclipse.jdt.internal.ui.javaeditor.AddImportOnSelectionAction:

private IStatusLineManager getStatusLineManager() {
    return fEditor.getEditorSite().getActionBars().getStatusLineManager();
}