Drag and drop between TreeViews

["Hajo Molegraaf" <hjausenet hotmail com>]

Hi,

I'm doing my first steps with programming in gtkmm (2.4) and there are a few 
things that I cannot get to work. One is drag and drop between TreeViews, 
like in a file browser. I found some hints on the internet 
(http://mail.gnome.org/archives/glademm-list/2004-January/msg00010.html), 
but it calls for programming skills that I do not (yet) have. There it is 
said that I "have to derive from the Model (!) [TreeStore] and override the 
dnd vfuncs". I tried it (hardly knowing what I'm doing) and it didn't work. 
Can someone explain me what to do? I added a short program where I tried to 
make things work. Only dnd within a TreeView works, and only the 
drag_data_delete_vfunc is called.

Thanks for the help,

Hajo Molegraaf


#include <gtkmm/main.h>
#include <gtkmm/window.h>
#include <gtkmm/paned.h>
#include <gtkmm/scrolledwindow.h>
#include <gtkmm/treeview.h>
#include <gtkmm/treestore.h>
#include <iostream>

class ModelColumns : public Gtk::TreeModel::ColumnRecord
{
public:
   ModelColumns() { add(text); }
   Gtk::TreeModelColumn<Glib::ustring> text;
};

class MyTreeStore : public Gtk::TreeStore
{
public:
   static Glib::RefPtr<MyTreeStore>
   MyTreeStore::create(const Gtk::TreeModelColumnRecord& cols)
   {
       MyTreeStore *x=new MyTreeStore(cols);
       x->reference();
       return Glib::RefPtr<MyTreeStore>(x);
   }

private:
   MyTreeStore(const Gtk::TreeModelColumnRecord& cols) : 
Gtk::TreeStore(cols) {}
   virtual bool drag_data_get_vfunc(const Gtk::TreeModel::Path& path,
       Gtk::SelectionData* selection_data);
   virtual bool drag_data_delete_vfunc(const Gtk::TreeModel::Path& path);
   virtual bool drag_data_received_vfunc(const Gtk::TreeModel::Path& dest, 
Gtk::SelectionData* selection_data);
};

bool MyTreeStore::drag_data_get_vfunc( const Gtk::TreeModel::Path& path,
   Gtk::SelectionData* selection_data )
{
   std::cout << "MyTreeStore::drag_data_get_vfunc\n";
   //what am I supposed to do here
   //what am I supposed to return
   return true;
}

bool MyTreeStore::drag_data_delete_vfunc( const Gtk::TreeModel::Path& path )
{
   std::cout << "MyTreeStore::drag_data_delete_vfunc\n";
   //what am I supposed to do here
   //what am I supposed to return
   return true;
}

bool MyTreeStore::drag_data_received_vfunc( const Gtk::TreeModel::Path& 
path,
   Gtk::SelectionData* selection_data )
{
   std::cout << "MyTreeStore::drag_data_received_vfunc\n";
   //what am I supposed to do here
   //what am I supposed to return
   return true;
}


class MyView : public Gtk::TreeView
{
public:
   MyView();
   ~MyView() {}

protected:
   void fill();
   ModelColumns model;
   Glib::RefPtr<MyTreeStore> store;
};

MyView::MyView() :
   store(MyTreeStore::create(model))
{
   set_model(store);
   append_column("Text", model.text);
   fill();

   // do I need to call these?
   enable_model_drag_dest();
   enable_model_drag_source();
}

void MyView::fill()
{
   Gtk::TreeModel::Row row;

   row = *(store->append());
   row[model.text] = "text A";
   row = *(store->append());
   row[model.text] = "text B";
   row = *(store->append());
   row[model.text] = "text C";
}

class MainWindow : public Gtk::Window
{
public:
   MainWindow();
   ~MainWindow() {}

protected:
   MyView view1, view2;
};

MainWindow::MainWindow()
{
   Gtk::HPaned* hpaned = Gtk::manage( new Gtk::HPaned() );
   Gtk::ScrolledWindow* sw1 = Gtk::manage( new Gtk::ScrolledWindow() );
   Gtk::ScrolledWindow* sw2 = Gtk::manage( new Gtk::ScrolledWindow() );

   sw1->add(view1);
   sw2->add(view2);
   hpaned->add1(*sw1);
   hpaned->add2(*sw2);

   add(*hpaned);
   show_all_children();
   set_default_size(640,480);
   set_title("Main Window");
   set_modal(false);
   property_window_position().set_value(Gtk::WIN_POS_CENTER);
   set_resizable(true);
}

int main (int argc, char *argv[])
{
 Gtk::Main kit(argc, argv);

 MainWindow mainWindow;
 Gtk::Main::run(mainWindow);

 return 0;
}

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