在QML中显示FPS [英] Show FPS in QML

问题描述

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，应用程序逻辑是在c ++中。

Is there a "simple" way to show the FPS (frame rate) in a QML/c++ application. All animations and views are done in QML and the application logic is in c++.

我已经尝试设置 QML_SHOW_FRAMERATE 在Linux中启动应用程序之前，但它没有帮助：

I already tried setting QML_SHOW_FRAMERATE in Linux before starting the application but it didn't help:

export QML_SHOW_FRAMERATE=1

推荐答案

您必须创建自己的FPS QQuickItem（或QQuickPaintedItem） .cpp在您的QML代码中可用。

You have to create your own FPS QQuickItem (or QQuickPaintedItem) and register in your main.cpp to be available in your QML code.

这里有一个示例。

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。

You can get any other implementation in Internet with a quick search.

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