Re: gtk_selection_get_selected()

[Owen Taylor <otaylor redhat com>]

On Tue, 2003-04-08 at 10:30, Jens Hornung wrote:
> Hi,
>
> i've got some problems with the function 'gtk_selection_get_selected'. Here's a part of the code:
>
> ...
> GtkListStore *list;
> GtkTreeView *view;
> GtkTreeSelection *selection;
> GtkTreeIter iter;
> GValue *value;
> ...
> selection = gtk_tree_view_get_selection(view);
> gtk_tree_selection_set_mode(selection, GTK_SELECTION_SINGLE);
> if((gtk_tree_selection_get_selected(GTK_TREE_SELECTION(selection),
>               GTK_TREE_MODEL(&list),
>               &iter))
>       == TRUE)
> {
>     gtk_tree_model_get_value(GTK_TREE_MODEL(list),
>               &iter,
>               1,
>               value);
>     g_printf("%s\n", (gchar *)value);
>     g_value_unset(value);
> }
> ...
>
>
> gcc always stops with the message:
>
> ad.c: In function `main':
> ad.c:360: warning: passing arg 2 of `gtk_tree_selection_get_selected' from incompatible pointer type
>
>
> Can someone give me a hint, how to do that right.

Well, hmmm, the way I'd write the above is:


GtkTreeModel *model;
GtkTreeView *view;
GtkTreeSelection *selection;
GtkTreeIter iter;

...
selection = gtk_tree_view_get_selection(view);
gtk_tree_selection_set_mode(selection, GTK_SELECTION_SINGLE);
if (gtk_tree_selection_get_selected(selection, &model, &iter))
{
    char *str;
    gtk_tree_model_get_value(model, &iter, 
                             1, &str, 
                             -1);
    g_print ("%s\n", str);
    g_free (str);
}

Explaining all the differences in detail would take a while, but
to answer your immediate question -

 GTK_TREE_MODEL (a)

is basically just a way of writing

 (GtkTreeModel *)a

But at the same time checking that 'a' really is a pointer to 
a tree model.

For this reason,

 GTK_TREE_MODEL (&list)

Can't work, since &list *isn't* a pointer to a tree model, it's
a pointer to the location where a pointer to the returned 
tree model will be stored. You could just use the straight C cast

 (GtkTreeModel **)&list

Or you could use a temporary variable of type GtkTreeModel.

 gtk_tree_selection_get_selected (..., &model, ...);
 list = GTK_TREE_MODEL (model);

Regards,
                                            Owen