Implementing TreeDragDest interface with a TreeModelSort model

[Christian Jodar <tian-ml c-sait net>]

Hello,

I'd like to enable drag and drop on a Gtk2::TreeView that contains a
Gtk2::TreeModelSort as its model (actually this one contains also a
Gtk2::TreeModelFilter which contains a Gtk2::TreeStore, but this has no impact
here).

But when I try to use drag and drop, I get an error message:


> Gtk-WARNING **: You must override the default 'drag_drop' handler on
> GtkTreeView when using models that don't support the GtkTreeDragDest
> interface and enabling drag-and-drop. The simplest way to do this is to
> connect to 'drag_drop' and call g_signal_stop_emission_by_name() in your
> signal handler to prevent the default handler from running. Look at the
> source code for the default handler in gtktreeview.c to get an idea what
> your handler should do. (gtktreeview.c is in the GTK source code.) If you're
> using GTK from a language other than C, there may be a more natural way to
> override default handlers, e.g. via derivation.


So I tried to add the interface to the TreeModelSort by implementing my own
class and planned to call the method from the underlying real model. But I
have the same error then, just as if the interface I added is ignored. I tried
to do as I found in documentation without any success.

I created a little program that reproduces this problem. I certainly did
something wrong with subclassing as it is the first time I used that. But I
don't know what as it seems to conform to the examples I saw and the print
shows correct list of interfaces. Find below the small program that shows my
problem. The error message is displayed when trying to drag and drop a row
anywhere else in the list.

Thank you for any help.

Christian Jodar.

#!/bin/perl

use strict;
use warnings;
use Data::Dumper;
use Gtk2;
Gtk2->init;

my $window = new Gtk2::Window('toplevel');

{
    package MyTreeModelSort;
    use Glib::Object::Subclass
        Gtk2::TreeModelSort::,
        interfaces => [ Gtk2::TreeDragDest:: ],
        ;

    sub new
    {
        my ($proto, $childModel) = @_;
        my $class = ref($proto) || $proto;
        my $self = Gtk2::TreeModelSort->new($childModel);
        bless ($self, $class);
        return $self;
    }
    sub DRAG_DATA_RECEIVED
    {
        print "DRAG_DATA_RECEIVED\n";
    }
    sub ROW_DROP_POSSIBLE
    {
        print "ROW_DROP_POSSIBLE\n";
    }
}

print "Interfaces :
\n",Dumper(Glib::Type->list_interfaces('MyTreeModelSort')),"\n"; my $model =
new Gtk2::TreeStore('Glib::String'); my $sorter = new MyTreeModelSort($model);
my $list = Gtk2::TreeView->new_with_model($sorter);
my $column = Gtk2::TreeViewColumn->new_with_attributes('Title',
Gtk2::CellRendererText->new, 'text' => 0); $list->append_column($column);

foreach ('a'..'z')
{
    my $iter = $model->append(undef);
    $model->set($iter, 0 => 'line'.$_);
}

my $targetEntryMove = {
    target => 'MY_ROW_TARGET',
    flags => ['same-widget'],
    info => 42,
};
$list->enable_model_drag_source('button1-mask','move', $targetEntryMove);
$list->enable_model_drag_dest('move', $targetEntryMove);

$window->add($list);
$window->signal_connect(destroy => sub { Gtk2->main_quit; });
$window->show_all;
Gtk2->main;