QQuickPaintedItem is not rendered in Layout

[Idodoqdo]

Hello everyone, I'm trying to render QQuickPaintedItem in QML. If I set its dimensions using width and height, then everything is fine, but if I put it in layout, then it stops being drawn

import QtQuick 2.15
import QtQuick.Window 2.15
import com.mycompany.messaging 1.0
import QtQuick.Layouts 1.15


Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    RowLayout {
        anchors.fill: parent
        GraphItem {
           id : gi
           objectName: "gI"
//           Layout.preferredWidth: parent.width / 2
//           Layout.preferredHeight:  parent.height / 2
//           implicitWidth: 10
//           implicitHeight: 10
           width: 1000
           height: 500
    //       width: parent.width
    //       height: parent.height
    //       anchors.fill: parent
        }
        Rectangle {
            color: "red"
            Layout.preferredWidth: parent.width / 2
            Layout.fillHeight: true

        }
    }

    Connections {
        target: video

        function onNewFrame(image, val) {
            gi.onNewFrame(image)
        }
    }
}

header

class GraphItem : public QQuickPaintedItem
{
    Q_OBJECT
    QML_ELEMENT

    Q_PROPERTY(VideoItem* videoItem READ getVideoItem WRITE setVideoItem)

public:
    GraphItem(QQuickPaintedItem *parent = nullptr)
        : QQuickPaintedItem(parent) {
    }

    QRectF boundingRect() const override{
        return _rect;
    }

    void paint(QPainter *painter) override {
        qDebug() << "1111";
        painter->drawImage(_rect, _image);
    }

    VideoItem * getVideoItem() {
        return _videoItem;
    }

    void setVideoItem(VideoItem* nItem) {
        connect(nItem, &VideoItem::newFrame, this, &GraphItem::onNewFrame
                /*,Qt::QueuedConnection*/);
        if (_videoItem) _videoItem->disconnect(_videoItem, Q_NULLPTR, this, Q_NULLPTR);
        _videoItem = nItem;
    }

public slots:
    void onNewFrame(QImage image){
        _image = image;
//        if(this->scene()!=Q_NULLPTR)this->scene()->update();
        update(_rect.toRect());
    }

protected:
    void itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value) override
    {
        if(change == ItemSceneChange ){
         _rect = QRectF(0, 0, width(), height());
        }
        return QQuickPaintedItem::itemChange(change, value);
    }
private:

    QImage _image;
    QRectF _rect;
    VideoItem * _videoItem;
};

[dheerendra]

@Idodoqdo

is paint(..) method is called ? Can you confirm.

[Idodoqdo]

@dheerendra
all the difficulties arise when I set the size via layout

[GrecKo]

@Idodoqdo I think you should use geometryChanged instead of itemChange. My guess is that itemChange is called only once where your size is null and then the layout resize your item but you are not aware.

[Idodoqdo]

@GrecKo
Thank you very much, it really helped

    void geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry) override {
        qDebug() << "new geo";
        _rect = newGeometry;
        QQuickPaintedItem::geometryChanged(newGeometry, oldGeometry);
//        update();
    }
//    void itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value) override
//    {
//        if(change == ItemSceneChange ){
//            qDebug() << "lol";
//            _rect = QRectF(0, 0, width(), height());
//        }
//        return QQuickPaintedItem::itemChange(change, value);
//    }