Re: Displaying a "hierarchy" of classes in a TreeView

[José Alburquerque <jaalburquerque cox net>]

Aaron Geier wrote:
> Hello,
>
> I'm not an expert on gtkmm, but I'll try to take a stab at this one.
>
> >From what I understand of TreeView is that the TreeView is the display and the TreeModel is the data that can be displayed by a TreeView.
>
> That being said, TreeView uses a class called CellRenderer[1] to display the view...
>
> So what you're attempting to do is add something that is not a CellRenderer to the TreeView display, which, I believe, cannot be done.
>
> You see, the TreeModel contains specific types of data (i.e. ustrings, integers, booleans, and doubles) and the TreeView has a way of displaying those types of data using CellRenderers.  By default, if you use a column that is a ustring, it will choose a CellRenderText as the CellRenderer, unless you tell it to use a different CellRenderer.
>
> Does that make any sense at all?
>
> -Aaron Geier
>
>   
Thanks Aaron for trying to answer my question.  As I mentioned in my 
original post, I have a series of "interconnected" classes (by 
pointers).  The connections are uni-directional which determines which 
is the parent and which are "ancestors".  Children, themselves can also 
have children so the tree relationship is somewhat "intricate".

As I mentioned in my last post, I think I found a solution:  What I've 
done so far is to derive all the classes from a single base class 
(though some have multiple inheritances) which I call "Element".  I then 
defined a class derived from Gtk::TreeModelColumnRecord class with a 
single Gtk::TreeModelColumn<Element> member which looks like the following:

   class Columns : public Gtk::TreeModelColumnRecord {
   public:
       Columns()
           { add(element); }
       Gtk::TreeModelColumn<Element> element;
   };

   Columns columns;

I can now successfully create the TreeStore (the model) using something like

   Gtk::RefPtr<Gtk::TreeStore> treeStoreRefPtr =
   Gtk::TreeStore::create(columns);


I am also able to "treeStoreRefPtr->append()" rows, etc. within the tree 
and set them by using code like the following:

   Gtk::TreeStore::iterator rowIter = treeStoreRefPtr->append();
   Gtk::TreeStore::Row row = (*rowIter);
   row[columns.element] = <One of My classes>;


So so far, I seem to be able to build the model just fine.

What I was asking basically is:  How can I have the TreeView "display" 
these classes and as you mentioned, the TreeView uses CellRenderers.  I 
found this excerpt from Chap. 8 of programming guide:


         Adding View Columns

   You can use the |append_column()| method to tell the View that it
   should display certain Model columns, in a certain order, with a
   certain column title.

     m_TreeView.append_column("Messages", m_Columns.m_col_text);
     

   When using this simple |append_column()| override, the |TreeView|
   will display the model data with an appropriate |CellRenderer|. For
   instance, strings and numbers are shown in a simple |Gtk::Entry|
   widget, and booleans are shown in a |Gtk::CheckButton|. This is
   usually what you need. *For other column types you must either
   connect a callback that converts your type into a string
   representation, with |TreeViewColumn::set_cell_data_func()|, or
   derive a custom |CellRenderer|.* Note that (unsigned) short is not
   supported by default - You could use (unsigned) int or (unsigned)
   long as the column type instead.


So I think I'll have to use the "set_cell_data_func()" in TreeViewColumn 
or derive a custom CellRenderer as mentioned above.  So far, I think 
things are working.  At first I didn't know where to start (it was a bit 
overwhelming), but  I think I should be able to figure things out now.  
If you have any comments I'd appreciate them and I'll post again if I 
get stuck.  :-)  Thanks again.

-Jose