使用鼠标控制地图

Tangram使用两种方式来控制地图：

1. 使用Gesture API
2. 使用Camera API

因为现在是在PC上控制， 因此使用了Camera API， 基本原理就是根据鼠标动作换算出camera变化量， 然后更新camera。

主要代码如下

Zoom在mouse wheelEvent里实现：

namespace Tangram {
class Map {
public:
    // Set the fractional zoom level of the view; if duration (in seconds) is provided,
    // zoom eases to the set value over the duration; calling either version of the setter
    // overrides all previous calls
    void setZoom(float _z);
    // Get the fractional zoom level of the view
    float getZoom();
};

void MapWidget::wheelEvent(QWheelEvent *event) {
    float zoom = m_map->getZoom();
    if(event->delta() > 0){
        zoom += 0.5;
    }else{
        zoom -= 0.5;
    }

    if (zoom > Max_Zoom_Level) {
        zoom = Max_Zoom_Level;
    }
    if (zoom < Min_Zoom_Level) {
        zoom = Min_Zoom_Level;
    }

    m_map->setZoom(zoom);
    update();
}
}

Rotate， Tilt和Pan在mouseMoveEvent里实现：

namespace Tangram {
class Map {
public:
    // Set the counter-clockwise rotation of the view in radians; 0 corresponds to
    // North pointing up; if duration (in seconds) is provided, rotation eases to the
    // the set value over the duration; calling either version of the setter overrides
    // all previous calls
    void setRotation(float _radians);
    // Get the counter-clockwise rotation of the view in radians; 0 corresponds to
    // North pointing up
    float getRotation();
    // Set the tilt angle of the view in radians; 0 corresponds to straight down;
    // if duration (in seconds) is provided, tilt eases to the set value over the
    // duration; calling either version of the setter overrides all previous calls
    void setTilt(float _radians);
    void setTiltEased(float _radians, float _duration, EaseType _e = EaseType::quint);
    // Get the tilt angle of the view in radians; 0 corresponds to straight down
    float getTilt();
};

static float getTilt(QPoint p0, QPoint p1) {
    return p1.y() - p0.x();
}

static float getRotation(QPoint p0, QPoint p1, QPoint center) {
    return QLineF(p1, center).angle() - QLineF(p0, center).angle();
}

void MapWidget::mouseMoveEvent(QMouseEvent *event) {
    auto pos = event->pos();
    if (m_gestureInprogress) {
        switch(m_gestureType) {
        case GESTURE_TAP:
            break;
        case GESTURE_PAN: {
            m_map->handlePanGesture(m_gestureStartPoint.x(), m_gestureStartPoint.y(), pos.x(), pos.y());
            m_gestureStartPoint = pos;
        }
        break;
        case GESTURE_SHOVE:{
            float currentTilt = toDegree(m_map->getTilt());
            float newTilt =  currentTilt + (pos.y() - m_gesturePreviousPoint.y());
            if(newTilt>60){
               newTilt = 60;
            } else if(newTilt<0) {
                newTilt = 0;
            }
            m_map->setTilt(toRadians(newTilt));
        }
        break;
        case GESTURE_ROTATE:{
            float currentRotation = m_map->getRotation();
            m_map->setRotation(currentRotation +
                               toRadians(getRotation(pos, m_gesturePreviousPoint, rect().center())));
        }
        break;
        default:
            break;
        }
    }
    m_gesturePreviousPoint = pos;
    update();
}
}

项目代码：

• https://github.com/tiangles/ltdmap
• https://github.com/tiangles/tangram-es