Re: Undo and Redo

[Paul Davis <paul linuxaudiosystems com>]

undo/redo is potentially a *very* complex thing to implement,
particularly if you want to be able to serialize it so that the
undo/redo state can be reloaded across program instances.

however, if you ignore that "detail", several years ago I and another
gtkmm/sigc++ enthusiast came up with what we considered a very elegant
undo/redo system that stores all "UndoableActions" using
sigc::signal<void> (i.e. a functor that can be called with no
arguments). by using sigc::bind, you can attach anything to the functor
that you need.

if your code is going to be released under the GPL, please feel free to
look at:

http://subversion.ardour.org/svn/ardour2/trunk/libs/pbd/undo.cc
http://subversion.ardour.org/svn/ardour2/trunk/libs/pbd/pbd/undo.h


http://subversion.ardour.org/svn/ardour2/trunk/libs/pbd/pbd/command.h

and lots more stuff in

http://subversion.ardour.org/svn/ardour2/trunk/libs/pbd/

the code has become more complex since we added serialization, but the
general idea should be fairly plain to see.

--p