OSG控制漫游二

添加鼠标控制场景：
按下鼠标左键左右拖动，场景左右移动；
按下鼠标左键上下拖动，场景上下移动。

//记录坐标
int mLeftX, mLeftY;
bool mLeftDown;

bool TravelManipulator::handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& us) {
    switch (ea.getEventType()) {
    case osgGA::GUIEventAdapter::KEYDOWN:
    if (ea.getKey()=='w'||ea.getKey()==osgGA::GUIEventAdapter::KEY_Up){
        mPosition[2] -= 0.5;
    } else if (ea.getKey() == 's' || ea.getKey() == osgGA::GUIEventAdapter::KEY_Down) {
        mPosition[2] += 0.5;
    } else if (ea.getKey() == 'a' || ea.getKey() == osgGA::GUIEventAdapter::KEY_Left) {
        mPosition[0] -= 0.5;
    } else if (ea.getKey() == 'd' || ea.getKey() == osgGA::GUIEventAdapter::KEY_Right) {
        mPosition[0] += 0.5;
    }else if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Home){
        mPosition[1] -= 0.5;
    } else if (ea.getKey() == osgGA::GUIEventAdapter::KEY_End) {
        mPosition[1] += 0.5;
    }
    break;
    case osgGA::GUIEventAdapter::PUSH:
    if (ea.getButton() == osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON){
        mLeftDown = true;
        mLeftX = ea.getX();
        mLeftY = ea.getY();
    }
    break;
    case osgGA::GUIEventAdapter::DRAG:
    if (mLeftDown){
        int deltaX = ea.getX() - mLeftX;
        int deltaY = ea.getY() - mLeftY;
        mPosition[0] -= osg::DegreesToRadians(0.01*deltaX);
        mPosition[1] -= osg::DegreesToRadians(0.01*deltaY);
    }
    break;
    case osgGA::GUIEventAdapter::RELEASE:
    if (ea.getButton() == osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON) {
        mLeftDown = false;
    }
    break;
    default:
    break;
    }
    return false;
}