QtQuickItem with custom opengl draw - after first frame, item dissapear

KrabQT

Basically i have this simple window with one GridLayout (for simplicity i added just one column and two rows).
In first row, i have GLViewer, which is QtQuickItem, that is drawing custom gl in beforeRendering slot ("inspired by this":http://qt-project.org/doc/qt-5/qtquick-scenegraph-openglunderqml-example.html )
When i run my app, all is ok, but when window is repainted (dragging or resizing, whatever causing repaint), my GLViewer dissapeared and i see ApplicationWindow background color instead (but paint method on GLViewer still called each repaint).

@import QtQuick 2.2
import QtQuick.Controls 1.1
import QtQuick.Layouts 1.1
import ge.components 1.0

ApplicationWindow {
visible: true
width: 1200
height: 700
title: qsTr("Hello World")
color: "#292929"

menuBar: MenuBar {
    Menu {
        title: qsTr("Filxe")
        MenuItem {
            text: qsTr("Exit")
            onTriggered: Qt.quit();
        }
    }
}

GridLayout {
    columns: 1
    rows: 2
    anchors.fill: parent

    Rectangle {
        color: "white"
        Layout.row: 2
        Layout.column: 1
        Layout.fillWidth: true
        Layout.fillHeight: true
    }

    GLViewer {
        Layout.row: 1
        Layout.column: 1
        Layout.fillWidth: true
        Layout.fillHeight: true
    }

}

}@

@#include "glviewer.h"
#include <QQuickWindow>
#include <iostream>
#include <QColor>

using namespace std;

GLViewer::GLViewer(QQuickItem parent) :
QQuickItem(parent)
{
connect(this, SIGNAL(windowChanged(QQuickWindow)), this, SLOT(handleWindowChanged(QQuickWindow*)));
}

void GLViewer::handleWindowChanged(QQuickWindow *win)
{
if (win) {
connect(win, SIGNAL(beforeRendering()), this, SLOT(paint()), Qt::DirectConnection);
win->setClearBeforeRendering(false);

}

void GLViewer::paint() {

QColor color = window()->color();
glClearColor(color.redF(), color.greenF(), color.blueF(), color.alphaF());
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

cout << "X: " << x() << ", Y: " << window()->height() - y() - height() << ", W: " << width() << ", H: " << height() << endl;

glViewport(x(), window()->height() - y() - height(), width(), height());

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

QColor top(127, 145, 166), bottom(24, 26, 28);

glBegin(GL_QUADS);
glColor3f(bottom.redF(), bottom.greenF(), bottom.blueF());
glVertex3f(-1.0f, -1.0f, 0.0f);
glVertex3f(1.0f, -1.0f, 0.0f);
glColor3f(top.redF(), top.greenF(), top.blueF());
glVertex3f(1.0f, 1.0f, 0.0f);
glVertex3f(-1.0f, 1.0f, 0.0f);
glEnd();

}
@

KrabQT

first frame:
!http://oi61.tinypic.com/2emzx9i.jpg(first frame)!

second frame:
!http://oi59.tinypic.com/2qv9x90.jpg(second frame)!

KrabQT

pleas Qt guys, does anyone know where is problem?