case 1: viewer->drag_mode = GIS_DRAG_PAN; break;
case 2: viewer->drag_mode = GIS_DRAG_ZOOM; break;
case 3: viewer->drag_mode = GIS_DRAG_TILT; break;
case 1: viewer->drag_mode = GIS_DRAG_PAN; break;
case 2: viewer->drag_mode = GIS_DRAG_ZOOM; break;
case 3: viewer->drag_mode = GIS_DRAG_TILT; break;