Minimum OSG QDockWidget bug problem.

cmakelists.txt

cmake_minimum_required(VERSION 2.8.11)


find_package(Qt5 REQUIRED COMPONENTS Gui Widgets Sql Core OpenGL Xml XmlPatterns )
		set(QT_LIBRARIES Qt5::Gui Qt5::Core Qt5::Widgets Qt5::Sql Qt5::OpenGL Qt5::Xml Qt5::XmlPatterns)

MACRO (QT_WRAP_UI output )
    FOREACH( input_file ${ARGN} )
        MESSAGE( STATUS "Generating header file from ${input_file}")
        QT5_WRAP_UI( ${output} ${input_file} )
    ENDFOREACH( input_file)
    SET_PROPERTY(SOURCE ${${output}} PROPERTY SKIP_AUTOGEN ON)
ENDMACRO(QT_WRAP_UI)

FIND_PACKAGE(osg)
FIND_PACKAGE(osgDB)
FIND_PACKAGE(osgUtil)
FIND_PACKAGE(osgGA)
FIND_PACKAGE(osgViewer)

set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_INCLUDE_CURRENT_DIR ON)

# Sources set
SET ( SOURCES
  custom_widget.h
  main.cpp
)



QT_WRAP_UI( UI_HEADERS mainUI.ui )

# Specify construction and link process
ADD_EXECUTABLE( prueba ${SOURCES} ${UI_HEADERS} ${MOC_SOURCES}   )
TARGET_LINK_LIBRARIES( prueba ${QT_LIBRARIES} ${OSG_LIBRARIES} ${OSGVIEWER_LIBRARIES} ${OSGUTIL_LIBRARIES} ${OSGDB_LIBRARIES} ${OSGGA_LIBRARIES} )

main.cpp

#include <QApplication>
#include <QMainWindow>
#include <QOpenGLWidget>
#include <QMouseEvent>
#include <QWheelEvent>
#include <QDesktopWidget>
#include <QScreen>
#include <QtGlobal>
#include <QWindow>
#include <QDockWidget>

#include <osg/ref_ptr>
#include <osgViewer/GraphicsWindow>
#include <osgViewer/Viewer>
#include <osg/Camera>
#include <osg/ShapeDrawable>
#include <osg/StateSet>
#include <osg/Material>
#include <osgGA/EventQueue>
#include <osgGA/TrackballManipulator>

#include <iostream>
#include <stdio.h>

class QtOSGWidget : public QOpenGLWidget
{
public:
	QtOSGWidget(qreal scaleX, qreal scaleY, QWidget* parent = 0)
			: QOpenGLWidget(parent)
			, _mGraphicsWindow(new osgViewer::GraphicsWindowEmbedded( this->x(), this->y(),
					this->width(), this->height() ) )
			, _mViewer(new osgViewer::Viewer)
			, m_scaleX(scaleX)
			, m_scaleY(scaleY)
	{
		osg::Cylinder* cylinder    = new osg::Cylinder( osg::Vec3( 0.f, 0.f, 0.f ), 0.25f, 0.5f );
		osg::ShapeDrawable* sd = new osg::ShapeDrawable( cylinder );
		sd->setColor( osg::Vec4( 0.8f, 0.5f, 0.2f, 1.f ) );
		osg::Geode* geode = new osg::Geode;
		geode->addDrawable(sd);

		osg::Camera* camera = new osg::Camera;
		camera->setViewport( 0, 0, this->width(), this->height() );
		camera->setClearColor( osg::Vec4( 0.9f, 0.9f, 1.f, 1.f ) );
		float aspectRatio = static_cast<float>( this->width()) / static_cast<float>( this->height() );
		camera->setProjectionMatrixAsPerspective( 30.f, aspectRatio, 1.f, 1000.f );
		camera->setGraphicsContext( _mGraphicsWindow );

		_mViewer->setCamera(camera);
		_mViewer->setSceneData(geode);
		osgGA::TrackballManipulator* manipulator = new osgGA::TrackballManipulator;
		manipulator->setAllowThrow( false );
		this->setMouseTracking(true);
		_mViewer->setCameraManipulator(manipulator);
		_mViewer->setThreadingModel(osgViewer::Viewer::SingleThreaded);
		_mViewer->realize();
	}


	virtual ~QtOSGWidget(){}

	void setScale(qreal X, qreal Y)
	{
		m_scaleX = X;
		m_scaleY = Y;
		this->resizeGL(this->width(), this->height());
	}

protected:

	virtual void paintGL() {
		_mViewer->frame();
	}

	virtual void resizeGL( int width, int height )
	{
		this->getEventQueue()->windowResize(this->x()*m_scaleX, this->y() * m_scaleY, width*m_scaleX, height*m_scaleY);
		_mGraphicsWindow->resized(this->x()*m_scaleX, this->y() * m_scaleY, width*m_scaleX, height*m_scaleY);
		osg::Camera* camera = _mViewer->getCamera();
		camera->setViewport(0, 0, this->width()*m_scaleX, this->height()* m_scaleY);
	}

	virtual void initializeGL(){
		osg::Geode* geode = dynamic_cast<osg::Geode*>(_mViewer->getSceneData());
		osg::StateSet* stateSet = geode->getOrCreateStateSet();
		osg::Material* material = new osg::Material;
		material->setColorMode( osg::Material::AMBIENT_AND_DIFFUSE );
		stateSet->setAttributeAndModes( material, osg::StateAttribute::ON );
		stateSet->setMode( GL_DEPTH_TEST, osg::StateAttribute::ON );
	}

	virtual void mouseMoveEvent(QMouseEvent* event)
	{
		this->getEventQueue()->mouseMotion(event->x()*m_scaleX, event->y()*m_scaleY);
	}

	virtual void mousePressEvent(QMouseEvent* event)
	{
		unsigned int button = 0;
		switch (event->button()){
		case Qt::LeftButton:
			button = 1;
			break;
		case Qt::MiddleButton:
			button = 2;
			break;
		case Qt::RightButton:
			button = 3;
			break;
		default:
			break;
		}
		this->getEventQueue()->mouseButtonPress(event->x()*m_scaleX, event->y()*m_scaleY, button);
	}

	virtual void mouseReleaseEvent(QMouseEvent* event)
	{
		unsigned int button = 0;
		switch (event->button()){
		case Qt::LeftButton:
			button = 1;
			break;
		case Qt::MiddleButton:
			button = 2;
			break;
		case Qt::RightButton:
			button = 3;
			break;
		default:
			break;
		}
		this->getEventQueue()->mouseButtonRelease(event->x()*m_scaleX, event->y()*m_scaleY, button);
	}

	virtual void wheelEvent(QWheelEvent* event)
	{
		int delta = event->delta();
		osgGA::GUIEventAdapter::ScrollingMotion motion = delta > 0 ?
														 osgGA::GUIEventAdapter::SCROLL_UP : osgGA::GUIEventAdapter::SCROLL_DOWN;
		this->getEventQueue()->mouseScroll(motion);
	}

	virtual bool event(QEvent* event)
	{
		bool handled = QOpenGLWidget::event(event);
		this->update();
		return handled;
	}

private:

	osgGA::EventQueue* getEventQueue() const {
		osgGA::EventQueue* eventQueue = _mGraphicsWindow->getEventQueue();
		return eventQueue;
	}

	osg::ref_ptr<osgViewer::GraphicsWindowEmbedded> _mGraphicsWindow;
	osg::ref_ptr<osgViewer::Viewer> _mViewer;
	qreal m_scaleX, m_scaleY;
};

int main(int argc, char** argv)
{
	QApplication qapp(argc, argv);

	QMainWindow window;
	QtOSGWidget* widget = new QtOSGWidget(1, 1, &window);
	QDockWidget *dock = new QDockWidget();
	dock->setWidget(widget);
	window.addDockWidget(Qt::RightDockWidgetArea, dock);
	window.show();

	return qapp.exec();
}

If you take the osg dock widget out of the main window, it stops showing the scene.