I use Qt5.12.0 on windows 10, I want to see if it's possible to set a qml window into my rootObject qml application window and draw in front of this child window.

Here is my actually code.

main.qml

Qt Code: 
  1. import QtQuick 2.9
  2. import QtQuick.Window 2.2
  3.  
  4. Window {
  5.     visible: true
  6.     width: 640
  7.     height: 480
  8.     title: qsTr("Hello World")
  9.     color: "transparent"
  10. }
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main.cpp

Qt Code: 
  1. #include <QApplication>
  2. #include <QQmlApplicationEngine>
  3.  
  4. #include "video.h"
  5.  
  6. #include <QQuickWindow>
  7. #include <QUrl>
  8.  
  9. int main(int argc, char *argv[])
  10. {
  11.     QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
  12.  
  13.     QApplication app(argc, argv);
  14.  
  15.     QQmlApplicationEngine engine;
  16.     engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
  17.     if (engine.rootObjects().isEmpty())
  18.         return -1;
  19.  
  20.  
  21.     QQuickWindow* window;
  22.     window = qobject_cast<QQuickWindow*>(engine.rootObjects().at(0));
  23.  
  24.     CVideo *_pVideo = new CVideo();
  25.     _pVideo->init(&engine, window);
  26.  
  27.     return app.exec();
  28. }
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video.h

Qt Code: 
  1. #ifndef VIDEO_H
  2. #define VIDEO_H
  3.  
  4. #include <QQmlApplicationEngine>
  5. #include <QQuickWindow>
  6.  
  7. class CVideo
  8. {
  9. public:
  10.     CVideo() = default;
  11.     void init(QQmlApplicationEngine* _engine, QQuickWindow* _pWindow);
  12. };
  13.  
  14. #endif
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video.cpp

Qt Code: 
  1. #include "video.h"
  2.  
  3. #include <gst/gst.h>
  4. #include <gst/video/videooverlay.h>
  5.  
  6. #include <QQmlComponent>
  7. #include <QQuickItem>
  8. #include <QQuickWindow>
  9.  
  10. void CVideo::init(QQmlApplicationEngine* _engine, QQuickWindow* _pWindow)
  11. {
  12.     gst_init(nullptr, nullptr);
  13.     GstElement *pipeline =
  14.            gst_parse_launch
  15.            (
  16.                 "rtspsrc location=rtsp://192.168.1.168:554/hdmi latency=50 ! application/x-rtp,media=(string)video ! decodebin ! glimagesink",
  17.            nullptr);
  18.     GstElement *sink  =  gst_bin_get_by_name(GST_BIN(pipeline), "sink");
  19.  
  20.  
  21.     WId xwinid = -1;
  22.     QQmlComponent *_pComponent = new QQmlComponent(_engine, QUrl(QStringLiteral("QML/VideoItem.qml")), _pWindow);
  23.     QQuickItem* _pVideoItem = qobject_cast<QQuickItem*>(_pComponent->create());
  24.     _pVideoItem->setParent(_pWindow);
  25.  
  26.     _pVideoItem->setParentItem(_pWindow->contentItem());
  27.     _pVideoItem->setProperty("id", "_videoOutput");
  28.     QObject *_pRootObject = dynamic_cast<QObject*>(_engine->rootObjects().first());
  29.     QList<QWindow*> _allWindow = _pRootObject->findChildren<QWindow*>();
  30.     QWindow *_window = _allWindow.first();
  31.     xwinid = _window->winId();
  32.     gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (sink), xwinid);
  33.     _window->setParent(_pWindow);
  34.  
  35.     GstStateChangeReturn sret = gst_element_set_state (pipeline,
  36.        GST_STATE_PLAYING);
  37.     if (sret == GST_STATE_CHANGE_FAILURE) {
  38.      gst_element_set_state (pipeline, GST_STATE_NULL);
  39.      gst_object_unref (pipeline);
  40.     }
  41. }
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VideoItem.qml

Qt Code: 
  1. import QtQuick 2.0
  2. import QtQuick.Window 2.3
  3. import QtQuick.Controls 2.4
  4.  
  5. Item{
  6.     id: _video
  7.     x: 0
  8.     y: 0
  9.     width: 1280
  10.     height: 800
  11.     visible: true
  12.  
  13.     Window{
  14.         id: _videoOutput
  15.         visible: true
  16.         x: 100
  17.         y: 100
  18.         width: 800
  19.         height: 600
  20.     }
  21.  
  22.     Button{
  23.         id: _button
  24.         x: 10
  25.         y: 10
  26.         width: 100
  27.         height: 100
  28.         text: "test"
  29.     }
  30. }
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With this code I see my video read by gstreamer (1.14.4) but my button is under the video, so I want it in front of it.

It's possible to draw qml item (label, button, image,...) in front of my video item ? Thanks in advance for your response.