// react to mouse motions with pressed buttons
void motion(int x, int y)
{
    mgr->mouseMove(x, y);

    if(_mousebuttons)
        _navigator.moveTo(x, y);
    _lastx = x;
    _lasty = y;

    glutPostRedisplay();
}
// react to mouse motions with pressed buttons
void motion(int x, int y)
{
    _mgr->mouseMove(x, y);
    glutPostRedisplay();
}
// react to mouse motions with pressed buttons
void motion(int x, int y)
{
    mgr->mouseMove(x, y);

    redisplay();
}