Re: Deriving from Gtk::ListStore

[Murray Cumming <murrayc murrayc com>]

On Wed, 2007-12-12 at 11:33 +0300, Andrew E. Makeev wrote:
> В Втр, 11/12/2007 в 12:53 -0600, Joaquim Schmidlap пишет:
> > We are going to be creating many TreeView/ListStore based applications here
> > that have to work with our in-house asynchronous message architecture. I've
> > successfully prototyped this kind of application by using a message queue.
> > Instead of writing directly to the model, I put the data on the message queue,
> > and use a Glib::Dispatcher to notify the Gtk thread to pull the data off the
> > queue and put it into the model. Works great, but requires several steps.
> > 
> > What I'd like to do is wrap those steps up so my users can still write to
> > the model via the Row::operator[] or Row::set_value() interfaces, and all
> > the queueing stuff would happen behind the scenes for them. I'd like to
> > leave the rest of the ListStore (and supporting class) interfaces alone as
> > much as possible.
> > 
> > Can anyone offer a roadmap or an example on how to proceed from here? At
> > first cut, it looks like deriving from ListStore is a lot of work, and might
> > require me to build my own iterator classes, etc. which seems like a lot of
> > work. Or, is there a better way to wrap up the behavior I want to hide?
> > 
> 
> Actually, there is not so much work to implement your own TreeModel.
> 
> Look at treemodelcustom/ example, and read documentation carefully
> (there are few method implementations missed in example to make it work
> completelly right).
> 
> And you should derive from TreeModel, TreeModelSortable (if you will
> implement sorting).
> 
> Unfortunatelly, you have to implement Iterator behavior, but that's not
> so complicated as you may think. You shall learn everything from
> example.

I still don't think that deriving a TreeModel is documented well enough,
but yes, it's possible.

Depending on the situation, you might also solve your problem by using
the cell_data_func() technique:
http://www.gtkmm.org/docs/gtkmm-2.4/docs/reference/html/classGtk_1_1TreeViewColumn.html#765296845c9e9757ba405becbbc13d96

That would allow you to store some reference/ID in the model, but get
the actual row values only when they are needed, maybe even using some
signal_idle() technique to get them asynchronously.

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