GtkTreeModel

[Christer Palm <palm nogui se>]

Hi!

A question for all you GtkTreeModel wizards out there;

I have implemented a custom GtkTreeModel to model a directory tree. For 
obvious performance reasons, I need to delay the scanning of a 
subdirectory until the user actually expands it. Thus, all directories 
will initially be assumed to contain subdirectories (i.e. my 
gtk_tree_model_iter_has_child() implementation speculatively returns true).

The tricky part is what happens if the user tries to expand a 
subdirectory which doesn't happen to contain any subdirectories. Just 
like the Windoze explorer (cough) directory view, I want the expander 
for that directory to "magically" disappear when the user tries to 
expand it.

However, just having the model change its mind turns out to be a very 
bad idea. I get messages like:

(DirectoryTreeTest:30175): Gtk-CRITICAL **: file gtktreeview.c: line 
3243 (gtk_tree_view_bin_expose): assertion `has_child' failed.
There is a disparity between the internal view of the GtkTreeView,
and the GtkTreeModel.  This generally means that the model has changed
without letting the view know.  Any display from now on is likely to
be incorrect.

all over the place...

How can I "let the view know" that the model has changed, and is it safe 
 to do it from within the GtkTreeModel implementation?

Cheers,
--
Christer Palm