Sets the modified state of the editor. Usually, the state is changed automatically after an insertion, deletion, or style change by calling this method. (This method is also called when the modification state changes through any method.) This method is usually not called when the state of the flag is not changing.
See also is-modified?.
Sets the modification state to modified?. If modified? is #f and the editor's undo or redo stack contains a system-created undoer that resets the modified state (because the preceding undo or redo action puts the editor back to a state where the modification state was #f), the undoer is disabled.