ECLIPSE RCP - lightweight decorator with objectState enablement

How use this functionality that org.eclipse.ui.decorators provides? Lets say I have some object in Tre开发者_如何学PythoneViewer and want to enable decorator only when object has "dirty" property set to true? Do I have to build some Decorator implementation or only use of objectState in plugin.xml extension will fulfill my needs?

This article may prove useful:

http://www.eclipse.org/articles/Article-Decorators/decorators.html

Also the extension point documentation:

http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fextension-points%2Forg_eclipse_ui_decorators.html

And the wiki:

http://wiki.eclipse.org/FAQ_How_do_I_create_a_label_decorator_declaratively%3F

And the platform help:

http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.platform.doc.isv/guide/workbench_advext_decorators.htm

"A brilliant colleague of mine" section in this post may be helpful In Eclipse RCP, how do I disable a save toolbar button according to the "dirty" property in editor