}

 bool GraphDisplayerCanvas::scrollEventHandler(GdkEvent* e)

 {

   bool handled=false;

   if(e->type==GDK_SCROLL)

     {

       //pointer shows this win point before zoom

       XY win_coord(((GdkEventScroll*)e)->x, ((GdkEventScroll*)e)->y);

       //the original scroll settings

       int scroll_offset_x, scroll_offset_y;

       get_scroll_offsets(scroll_offset_x, scroll_offset_y);

       //pointer shows this canvas point before zoom

       XY canvas_coord;

       window_to_world(win_coord.x, win_coord.y, canvas_coord.x, canvas_coord.y);

       if(((GdkEventScroll*)e)->direction) //IN

 	{

 	  zoomIn();

 	}

       else

 	{

 	  zoomOut();

 	}

       //pointer shows this window point after zoom

       XY post_win_coord;

       world_to_window(canvas_coord.x, canvas_coord.y, post_win_coord.x, post_win_coord.y);

       //we have to add the difference between new and old window point to original scroll offset

       scroll_to(scroll_offset_x+(int)(post_win_coord.x-win_coord.x),scroll_offset_y+(int)(post_win_coord.y-win_coord.y));

       //no other eventhandler is needed

       handled=true;

     }

   return handled;