Mouse drag without holding LMB

function mouse_rotation_cb(rot_x, rot_y) {
        m_phy.character_rotation_inc(_character, rot_x, 0);
        if (rot_y) {
            m_cam.eye_rotate(camobj, 0, rot_y);

            m_cam.get_camera_angles(camobj, _vec3_tmp);
            offset[2] = -dist * Math.cos(_vec3_tmp[1]);
            offset[1] = -dist * Math.sin(_vec3_tmp[1]);

            m_cons.remove(camobj)
            m_cons.append_semi_stiff_cam(camobj, character, offset);
        }
    }
	
	var canvas_elem = m_container.get_canvas();
	canvas_elem.addEventListener("mousemove", function(e) {
        m_mouse.request_mouse_drag(canvas_elem, null, mouse_rotation_cb);
    }, false);