I have been trying to write a text editor based on Eclipse plug-in. I used AbstractTextEditor and AbstractDocumentProvider classes.Everything goes ok. But I didn't like undo mechanism. For example I'm typing three line and then pressed CNTRL+Z and all text disappeared. I debug all of the undo mechanism like DocumnetUndoManager and other classes and didn't come up with a solution. Is there any rule mechanism for undo operation like when use pressed space add state to undo history or other classes the implements this behavior ?