Re: fine-tune drag'n'drop in a tree

[Ionutz Borcoman <iborco gmail com>]

On Wednesday 07 May 2008 2:25:22 pm Murray Cumming wrote:
> On Sat, 2008-05-03 at 13:29 +0300, Ionutz Borcoman wrote:
> You can do this by overriding the row_drop_possible_vfunc() virtual
> method. You can then add any logic you like, usually examining the
> relevant model data for that row.
>
> I do that in Glom's (ugly) layout dialog. For instance, text items can
> be dropped into group items, but not into other text items:
> http://svn.gnome.org/viewvc/glom/trunk/glom/mode_data/treestore_layout.h?vi
>ew=markup
> http://svn.gnome.org/viewvc/glom/trunk/glom/mode_data/treestore_layout.cc?v
>iew=markup
>
> It works well, so we should probably mention in the documentation.

After some more testing with the example from gtkmm tutorial I have managed to 
find the effect I was looking for - I had simply to return false when the 
parent row is top level or empty:

	Gtk::TreeModel::Path dest_parent = dest;
	bool dest_is_not_top_level = dest_parent.up();
	if(!dest_is_not_top_level || dest_parent.empty())
	{
		return false;
	}

Can somebody please explain when these cases happen? I assume I get 
dest_is_not_top_level if the item is the root item, but when do I get 
dest_parent.empty()?

Other question related with the D&D in a tree (not critical, but nice to 
have): how can I change the cursor displayed during the drag? For example to 
display an image, or to add a "+" or "-" to the current image displayed.

And thanx for all of you that stopped me falling to the dark side of qt :-D

Cheers,

Johnny