As a somewhat related topic (this thread seems to not be nailed on a very
specific topic yet and this still fits in i think), a changeset+commit API
(in the truer sense; not what was proposed with just saying "all nodes below
this one have changed") would be _very_ welcome for gtkmm, because right
now, setting row data looks like this (snippet from our code):
--snip--
void
Playlist_V::put_track_at_iter (Track const& track,
Gtk::TreeModel::iterator & iter)
{
(*iter)[m_track_cr.track] = track;
(*iter)[m_track_cr.uid] = track.bmpx_track_id ;
(*iter)[m_track_cr.localUid] = m_localUid;
(*iter)[m_track_cr.searchKey] = track.title ? track.title.get() :
std::string();
(*iter)[m_track_cr.playTrack] = track.active.get();
--snip--
And yes, this is exactly how it looks like: The row is accessed for each of
those lines, and each uses a separate call to list_store_set() internally.
Yes, it i disastrous to performance. One guy on the gtkmm-devel list
recently made a benchmark and found that the gtkmm way of doing this is
approximately 75 times (not 75% -- 75 times) slower than the C Gtk+ method.
Now without going to deep into C++, let's just say that with the way gtkmm
at least works, if not to be sane C++ altogether, it's not possible to have
a C-like TreeModel API in gtkmm, and that's where the changesets come in.
I've been already thinking of a transactional system for TreeModel, and i
have some ideas, but nothing that could be put to code right now.
_However_, a native API for this in C TreeModel (perhaps an additional
interface to TreeModel? "GtkTreeModelTransactional"?) would make this task
very simple because then it could be normally wrapped without needing
gtkmm-specific API.
Kris if you are really on to having a TreeModelTransactional Iface, please
just say "yeah", and i'll also start working on something (deadchip in
#gtk+, btw). This would be a major help for the other discussed problems
here, as well as for this one.
-- Milosz
On 6/24/07, Kristian Rietveld <[EMAIL PROTECTED]> wrote:
>
> On Tue, Jun 19, 2007 at 12:45:09PM +0100, Peter Clifton wrote:
> > This seems to break the MVC abstraction - if the model changes
> > drastically, I need to know which tree-views are connected so I can
> > disconnect them? Bad!
> >
> > We need some new API I guess - which signals any connected views that
> > the data it has cached about the model should be invalidated, and that
> > the model may be changing without emitting signals.
> >
> > Once the model is updated, a further signal will inform the view that it
> > can keep cached state again.
>
> In practise this won't be all that different compared to setting a new
> model on the tree view, except that with a signal it will be initiated
> from the model. After the model emits the "I am finished changing
> everything" signal, the tree view will have to rebuild its internal
> rbtree by iterating over the full model again (any other model that is
> connected to this model will have to rebuild its internal state tree
> too), since it has no clue what has changed. This will probably also
> involve unreferencing all nodes when the model emits "invalidate" and
> re-reference the new nodes after the mass changing, and remembering
> selection and expansion state during the mass-changing (this information
> is kept in the internal rbtree too), etc.
>
> I think a much better solution would be to be able to group a bunch of
> changes together in a kind of "atomic changeset" which is then emitted
> with a single signal. All connected views/models could then process the
> full changeset in one pass. (Possibly this could also add/remove ranges
> of nodes, etc).
>
>
> regards,
>
> -kris.
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>
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