在mac book pro上视频的实际显示大小是width/height的2分之1

[JavinYang]

在mac book pro上视频的实际显示大小是width/height的2分之1。为什么？和分辨的PPI有关吗？怎么解决?

[JavinYang]

// 我在这里*2 绘制尺寸才正常

void AVideoWidget::paint(QPainter *painter)
{
    if (!m_render)
        return;

    painter->beginNativePainting();

    if (!m_render->isInitialized())
        // 我在这里*2 绘制尺寸才正常
        m_render->initialize(width()*2, height()*2);

    {
    std::lock_guard<std::mutex> lock(m_mutex);
    m_render->setFrameInfo(m_rotation, m_mirrored);
    if (m_frame)
        m_render->renderFrame(*m_frame);
    }

    painter->endNativePainting();
}

设备像素比（devicePixelRatio）： 设备像素比 = 设备像素 / 设备独立像素。(在Retina屏的iphone上，DPR为2，1个css像素相当于2个物理像素)

我是试图调用 qDebug() << painter->device()->devicePixelRatioF(); 不过打印是1 很奇怪按理说视网膜屏应该是2，我的就是retina屏。

https://doc.qt.io/qt-5/qpaintdevice.html#devicePixelRatioF

我发现

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QApplication app(argc, argv);
    app.setOrganizationName("Agora");
    app.setOrganizationDomain("agora.io");

    qmlRegisterType<AVideoWidget>("AVideoWidget", 1, 0, "AVideoWidget");

    MainWindow w;
    // 通过这样获取devicePixelRatioF就是2
    qDebug() << w.devicePixelRatioF(); 
    w.show();
    return app.exec();
}

但是通过AVideoWidget的paint

void AVideoWidget::paint(QPainter *painter)
{
    if (!m_render)
        return;

    painter->beginNativePainting();
    // 这个结果是1
    qDebug() << painter->device()->devicePixelRatioF();

    if (!m_render->isInitialized())
        m_render->initialize(width()*2, height()*2);

    {
    std::lock_guard<std::mutex> lock(m_mutex);
    m_render->setFrameInfo(m_rotation, m_mirrored);
    if (m_frame)
        m_render->renderFrame(*m_frame);
    }

    painter->endNativePainting();
}

AVideoWidget继承了QQuickPaintedItem看来QQuickPaintedItem出现了什么问题。

最终的解决方法是

void AVideoWidget::handleWindowChanged(QQuickWindow *win)
{
    if (win)
    {
        // 修改这里 这样devicePixelRatio的值是正确的 视网膜屏为2
        m_devicePixelRatio = win->devicePixelRatio();
        connect(win, SIGNAL(sceneGraphInvalidated()), this, SLOT(cleanup()), Qt::DirectConnection);
    }
}

void AVideoWidget::paint(QPainter *painter)
{
    if (!m_render)
        return;

    painter->beginNativePainting();

    if (!m_render->isInitialized())
        // 修改这里
        m_render->initialize(width()*m_devicePixelRatio, height()*m_devicePixelRatio);

    {
    std::lock_guard<std::mutex> lock(m_mutex);
    m_render->setFrameInfo(m_rotation, m_mirrored);
    if (m_frame)
        m_render->renderFrame(*m_frame);
    }

    painter->endNativePainting();
}

avideowidget.h

#ifndef AVIDEOCANVAS_H
#define AVIDEOCANVAS_H

#include <QQuickPaintedItem>
#include <mutex>
#include <memory>

namespace agora { namespace media {
    class IVideoFrame;
}}

class VideoRendererOpenGL;

class AVideoWidget : public QQuickPaintedItem
{
	Q_OBJECT
public:
    AVideoWidget(QQuickItem *parent = 0);
    ~AVideoWidget();
    int setViewProperties(int zOrder, float left, float top, float right, float bottom);
    int deliverFrame(const agora::media::IVideoFrame& videoFrame, int rotation, bool mirrored);
    virtual void paint(QPainter *painter) Q_DECL_OVERRIDE;
protected:
    virtual void geometryChanged(const QRectF& newGeometry, const QRectF& oldGeometry) Q_DECL_OVERRIDE;
signals:
    void frameDelivered();
    void widgetInvalidated();
    void viewSizeChanged(int width, int height);

public slots:
    void renderFrame();
    void handleWindowChanged(QQuickWindow *win);
    void cleanup();
private:
    std::unique_ptr<VideoRendererOpenGL> m_render;
    std::mutex m_mutex;
    //usage of m_frame should be guarded by m_mutex
    agora::media::IVideoFrame* m_frame;
    int m_rotation;
    bool m_mirrored;
    qreal m_devicePixelRatio; // 修改这里
};

#endif // AVIDEOCANVAS_H

[plutoless]

您用的native sdk版本是？

[JavinYang]

您用的本地sdk版本是？

macOS v3.1.2

[plutoless]

@JavinYang ioquake/ioq3#422
您可以参考这里调整下plist配置或者修改opengl，这应该是catalina后引入的问题

[JavinYang]

在我的mac book pro上全屏显示相当烫手 小窗口还行

[plutoless]

@JavinYang 您可以试试我们的非Qt版本是否有类似的情况，或者这边可以简单做个profiling看下性能消耗在哪块吗？