Program crashes dragging a custom item derived from itemsimple

[Shashank Bandari <mail shashank-bandari in>]

Hi,

   I am trying to develop a power system software and need to draw movable components onto to the screen. However I face the following issues during implementation:

 

1. The object is displayed on mouse click. When I try to drag the custom object, the program crashes. If I remove the "moved_object->changed(true);  " statement in the "on_canvas_motion_notify_event" function, the program runs but the object is not moved.

 

2. When I now minimize the window and then maximize the object has moved

 

3. When I try to move the object once again the get_item_at() returns 0

 

Can someone help me out here as I have no clue how to proceed further.

 

#include <gtkmm.h>
#include <goocanvasmm.h>

 

class MainWindow:public Gtk::Window
{
    public:
        Glib::RefPtr<Gtk::Builder> ref_glade;
        MainWindow(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder);
        Goocanvas::Canvas canvas_area;
        Glib::RefPtr<Goocanvas::Item> dragitem;
        bool isDragged;
        bool on_canvas_button_press_event(const Glib::RefPtr<Goocanvas::Item>& item, GdkEventButton* event);
        bool on_canvas_button_release_event(const Glib::RefPtr<Goocanvas::Item>& item, GdkEventButton* event);
        bool on_canvas_motion_notify_event(const Glib::RefPtr<Goocanvas::Item>& target, GdkEventMotion* event);
};

class SampleObject : public Goocanvas::ItemSimple
{
public:
  SampleObject(double x = 0, double y = 0);

  void simple_update_vfunc(const Cairo::RefPtr<Cairo::Context>& cr);
  void simple_paint_vfunc(const Cairo::RefPtr<Cairo::Context>& cr, const Goocanvas::Bounds& bounds);
    bool simple_is_item_at_vfunc(double x, double y, const Cairo::RefPtr< Cairo::Context >& cr, bool is_pointer_event);
  double obj_x, obj_y;

};

 

MainWindow::MainWindow(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
: Gtk::Window(cobject),
ref_glade(builder)
{    
    isDragged=false;
    canvas_area.set_size_request(640, 480);
    canvas_area.set_bounds(0, 0, 1000, 1000);
    Gtk::ScrolledWindow* scroll_win = 0;
    builder->get_widget("scrolledwindow1", scroll_win);
    scroll_win->add(canvas_area);
    show_all_children();
    
    Glib::RefPtr<Goocanvas::Item> root = canvas_area.get_root_item();
    root->signal_button_press_event().connect(sigc::mem_fun(*this, &MainWindow::on_canvas_button_press_event));
    root->signal_button_release_event().connect(sigc::mem_fun(*this, &MainWindow::on_canvas_button_release_event));
    root->signal_motion_notify_event().connect(sigc::mem_fun(*this, &MainWindow::on_canvas_motion_notify_event));
}

bool MainWindow::on_canvas_button_release_event(const Glib::RefPtr<Goocanvas::Item>& item, GdkEventButton* event)
{
    isDragged=false;
    dragitem.clear();
    return true;
}

bool MainWindow::on_canvas_motion_notify_event(const Glib::RefPtr<Goocanvas::Item>& target, GdkEventMotion* event)
{
    if(isDragged)
    {
        Glib::RefPtr<SampleObject> moved_object=Glib::RefPtr<SampleObject>::cast_dynamic(dragitem);
        moved_object->obj_x=event->x;
        moved_object->obj_y=event->y;
        moved_object->changed(true);    
    }
    return true;
}
bool MainWindow::on_canvas_button_press_event(const Glib::RefPtr<Goocanvas::Item>& item, GdkEventButton* event)
{
    Glib::RefPtr<Goocanvas::Item> root = canvas_area.get_root_item();
    Glib::RefPtr<Glib::Object> select_object=ref_glade->get_object("add_select");
    Glib::RefPtr<Gtk::RadioAction> select_selected = Glib::RefPtr<Gtk::RadioAction>::cast_dynamic(select_object);
    switch(select_selected->get_current_value())
    {
        case 1:        
        {
            Glib::RefPtr<SampleObject> sobj=Glib::RefPtr<SampleObject>(new SampleObject(event->x,event->y));
            root->add_child(sobj);
        break;
        }
        default:
            dragitem=canvas_area.get_item_at(event->x,event->y,true);
            std::cout<<dragitem<<std::endl;
            if(dragitem)
            {
                isDragged=true;
            }
        break;
    }
    return true;
}

 

 

--

Thanking You,
Shashank Bandari





shashank bandari ieee org