在QML中显示FPS

Question

是否有一种"简单"的方式来显示QML/c ++应用程序中的FPS(帧速率).所有动画和视图都在QML中完成,应用程序逻辑在c ++中.

我已经尝试QML_SHOW_FRAMERATE在启动应用程序之前在Linux中进行设置,但它没有帮助:

export QML_SHOW_FRAMERATE=1

Answer 1

您必须创建自己的FPS QQuickItem(或QQuickPaintedItem)并在main.cpp中注册才能在QML代码中使用.

这是一个例子.

class FPSText: public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(int fps READ fps NOTIFY fpsChanged)
public:
    FPSText(QQuickItem *parent = 0);
    ~FPSText();
    void paint(QPainter *);
    Q_INVOKABLE int fps()const;

signals:
    void fpsChanged(int);

private:
    void recalculateFPS();
    int _currentFPS;
    int _cacheCount;
    QVector<qint64> _times;
};

FPSText::FPSText(QQuickItem *parent): QQuickPaintedItem(parent), _currentFPS(0), _cacheCount(0)
{
    _times.clear();
    setFlag(QQuickItem::ItemHasContents);
}

FPSText::~FPSText()
{
}

void FPSText::recalculateFPS()
{
    qint64 currentTime = QDateTime::currentDateTime().toMSecsSinceEpoch();
    _times.push_back(currentTime);

    while (_times[0] < currentTime - 1000) {
        _times.pop_front();
    }

    int currentCount = _times.length();
    _currentFPS = (currentCount + _cacheCount) / 2;
    qDebug() << _currentFPS;

    if (currentCount != _cacheCount) fpsChanged(_currentFPS);

    _cacheCount = currentCount;
}

int FPSText::fps()const
{
    return _currentFPS;
}

void FPSText::paint(QPainter *painter)
{
    recalculateFPS();
    //qDebug() << __FUNCTION__;
    QBrush brush(Qt::yellow);

    painter->setBrush(brush);
    painter->setPen(Qt::NoPen);
    painter->setRenderHint(QPainter::Antialiasing);
    painter->drawRoundedRect(0, 0, boundingRect().width(), boundingRect().height(), 0, 0);
    update();
}

QML:

FPSText{
        id: fps_text
        x:0
        y: 0;
        width: 200
        height: 100
        Text {
                anchors.centerIn: parent
                text: fps_text.fps.toFixed(2)
            }
    }

您可以通过快速搜索在Internet上获得任何其他实现.

Answer 2

QML FPS Counter，不影响性能。

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QNanoPainter和 qt-labs 中的其他人的项目正在使用 QML 项的动画刷新来创建 FPS 计数器。这很容易完成，附上一个使用此技术的项目（从QNanoPainter FPS 计数器修改）。

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Fps项目代码：

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import QtQuick 2.0\nimport QtQuick.Window 2.2\n\nRectangle {\n    id: root\n    property int frameCounter: 0\n    property int frameCounterAvg: 0\n    property int counter: 0\n    property int fps: 0\n    property int fpsAvg: 0\n\n    readonly property real dp: Screen.pixelDensity * 25.4/160\n\n    color: "black"\n    width:  childrenRect.width + 10*dp;\n    height: childrenRect.height + 10*dp;\n\n    Image {\n        id: spinnerImage\n        anchors.verticalCenter: parent.verticalCenter\n        x: 4 * dp\n        width: 36 * dp\n        height: width\n        source: "images/spinner.png"\n        NumberAnimation on rotation {\n            from:0\n            to: 360\n            duration: 800\n            loops: Animation.Infinite\n        }\n        onRotationChanged: frameCounter++;\n    }\n\n    Text {\n        anchors.left: spinnerImage.right\n        anchors.leftMargin: 8 * dp\n        anchors.verticalCenter: spinnerImage.verticalCenter\n        color: "#c0c0c0"\n        font.pixelSize: 18 * dp\n        text: "\xc3\x98 " + root.fpsAvg + " | " + root.fps + " fps"\n    }\n\n    Timer {\n        interval: 2000\n        repeat: true\n        running: true\n        onTriggered: {\n            frameCounterAvg += frameCounter;\n            root.fps = frameCounter/2;\n            counter++;\n            frameCounter = 0;\n            if (counter >= 3) {\n                root.fpsAvg = frameCounterAvg/(2*counter)\n                frameCounterAvg = 0;\n                counter = 0;\n            }\n        }\n    }\n}\n

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将其用作：

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import QtQuick 2.9\nimport QtQuick.Window 2.2\n\nWindow {\n    visible: true\n    width: 640\n    height: 480\n    title: qsTr("Hello World")\n\n    FpsItem {\n        id: fpsItem\n        anchors.centerIn: parent\n    }\n\n}\n

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