== State Parameters and Transitions ==

Something like this gains access to a lot of view parameters:
{{{
for n in dir(chimera.viewer): print n, eval('type(chimera.viewer.%s)' % n)
}}}

Some tips in the [http://www.cgl.ucsf.edu/chimera/docs/ProgrammersGuide/faq.html programming FAQ] are useful (esp, items 4, 5, 7-10).  Note, take a look at the code for {{{chimera.update.checkForChanges()}}}, as this may be helpful in detecting changes for transitions and for checking the validity of state parameters.

{{{chimera.OpenModels.addRemoveHandler(func, data)}}} can be used to add a trigger handler when removing models.  This might be useful in the creation of a state instance as a way to maintain integrity or validity of the saved state.  It may depend on whether the state instance keeps a reference or a copy of models in the saved state.  For efficiency, it is better to keep a reference.  For validity, it could be better to keep a copy.  Perhaps a copy is required only when a model is removed, so the copy action could be triggered then.