Why does adding a QWidget to a QQuickPaintedItem's QML fail to display?

[mirro]

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <widgetitem.h>
#include <QProgressBar>
#include <QPushButton>
#include <QTimer>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QQmlApplicationEngine engine;
    qmlRegisterType<WidgetItem>("WidgetItem", 1, 0, "WidgetItem");

    const QUrl url(QStringLiteral("qrc:/main.qml"));

    WidgetItem* widgetItem = nullptr;

    QPushButton button("good old push button");

    // Could we move this inside WidgetItem?
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     [&button, &widgetItem](QObject* object, const QUrl /*&url*/) {
        widgetItem = object->findChild<WidgetItem*>();
        Q_ASSERT(widgetItem);
        widgetItem->setWidget(&button);
    });
    //
    QQmlContext* pContext = engine.rootContext();
    pContext->setContextProperty("WidgetItem",widgetItem);
    engine.load(url);

    return app.exec();
}


import QtQuick 2.12
import QtQuick.Window 2.12
import WidgetItem 1.0

Window {
    visible: true
    width: 450
    height: 70
    title: qsTr("Hello Widget")

    Rectangle {
        anchors.fill: parent
        Text {
            id: text
            anchors.margins: 20
            text: "This text is created with QML, the item below is a QWidget:"
        }

        WidgetItem {
            anchors.top: text.bottom
            anchors.topMargin: 15
            width: parent.width
            height: parent.height - text.height
        }
    }

    Shortcut {
        sequence: "Ctrl+q"
        onActivated: Qt.quit()
    }
}

#ifndef WIDGETITEM_H
#define WIDGETITEM_H

#include <QQuickPaintedItem>
#include <QWidget>
#include <QPointer>

class WidgetItem : public QQuickPaintedItem
{
    Q_OBJECT

public:
    WidgetItem(QQuickItem* parent = nullptr);

    void setWidget(QWidget* widget);

    virtual void paint(QPainter* painter) override;

protected:

    void mousePressEvent(QMouseEvent* event) override;
    void mouseReleaseEvent(QMouseEvent* event) override;

private:
    QPointer<QWidget> m_widget;
};

#include "widgetitem.h"

#include <QPainter>
#include <QTimer>

WidgetItem::WidgetItem(QQuickItem *parent) : QQuickPaintedItem(parent)
{
    setAcceptTouchEvents(true);
    setAcceptedMouseButtons(Qt::AllButtons);
}

void WidgetItem::setWidget(QWidget *widget)
{
    m_widget = widget;
}

void WidgetItem::paint(QPainter *painter)
{
    if(m_widget) {
        m_widget->render(painter);
    }
}

void WidgetItem::mousePressEvent(QMouseEvent *event)
{
    if(m_widget) {
        QCoreApplication::sendEvent(m_widget, event);
        update();
    }
}

void WidgetItem::mouseReleaseEvent(QMouseEvent *event)
{
    if(m_widget) {
        QCoreApplication::sendEvent(m_widget, event);
        update();
    }
}

[SGaist]

Hi,

You should take a look at KDAB's DeclarativeWidgets project.