Hello,

I have a problem integrating Ogre in QtMdiArea (not with QWidget, it's work fine!).
I'm pretty sure that the problem is Qt, because I have checked all the Ogre Code, and it's working with a simple QWidget.
You can see I have derived OgreWidget from QMdiSubWindow instead of QWidget because it's working better than QWidget with QMdiArea. I will post the Visual Solution tomorrow if you want.

Here is my source code :

OgreApplication.h :
#ifndef OGREAPPLICATION_H
#define OGREAPPLICATION_H

#include <QObject>
#include <Ogre.h>

class OgreWidget;

class OgreApplication : public QObject
{
Q_OBJECT

public:
OgreApplication(QObject *parent = 0);
~OgreApplication();
void setupNLoadResources();
void createScene();

public slots:
void initialise();
OgreWidget * createOgreWidget();

private:
Ogre::Root *ogreRoot;
Ogre::SceneManager *ogreSceneManager;
static int nbRenderWindows;
};

#endif // OGREAPPLICATION_H
OgreApplication.cpp :
#include "OgreApplication.h"

#include "OgreWidget.h"

int OgreApplication::nbRenderWindows = 0;

OgreApplication::OgreApplication(QObject *parent)
: QObject(parent),
ogreRoot(0),
ogreSceneManager(0)
{

}

OgreApplication::~OgreApplication()
{
if(ogreRoot)
{
if(ogreSceneManager)
{
ogreRoot->destroySceneManager(ogreSceneManager);
}
}

delete ogreRoot;
}

void OgreApplication::initialise()
{
if (ogreRoot == NULL)
{
ogreRoot = new Ogre::Root();
}

// initialised ?
if (!ogreRoot->isInitialised())
{
Ogre::RenderSystem *renderSystem = ogreRoot->getRenderSystemByName("OpenGL Rendering Subsystem");
ogreRoot->setRenderSystem(renderSystem);
ogreRoot->initialise(false);
// Verify initialisation after initialise root
if (!ogreRoot->isInitialised())
{
return;
}
}
else
{
return;
}

ogreSceneManager = ogreRoot->createSceneManager(Ogre::ST_GENERIC);
}

OgreWidget * OgreApplication::createOgreWidget()
{
nbRenderWindows++;
OgreWidget * og = new OgreWidget();
og->initialise(nbRenderWindows, ogreRoot, ogreSceneManager);

if (nbRenderWindows == 1)
{
setupNLoadResources();
createScene();
}

return og;
}

void OgreApplication::setupNLoadResources()
{
// Load resource paths from config file
Ogre::ConfigFile cf;
cf.load("resources.cfg");

// Go through all sections & settings in the file
Ogre::ConfigFile::SectionIterator seci = cf.getSectionIterator();

Ogre::String secName, typeName, archName;
while (seci.hasMoreElements())
{
secName = seci.peekNextKey();
Ogre::ConfigFile::SettingsMultiMap *settings = seci.getNext();
Ogre::ConfigFile::SettingsMultiMap::iterator i;
for (i = settings->begin(); i != settings->end(); ++i)
{
typeName = i->first;
archName = i->second;
#if OGRE_PLATFORM == OGRE_PLATFORM_APPLE
// OS X does not set the working directory relative to the app,
// In order to make things portable on OS X we need to provide
// the loading with it's own bundle path location
Ogre::ResourceGroupManager::getSingleton().addResourceLocation(
Ogre::String(macBundlePath() + "/" + archName), typeName, secName);
#else
Ogre::ResourceGroupManager::getSingleton().addResourceLocation(
archName, typeName, secName);
#endif
}
}

// Initialise, parse scripts etc
Ogre::ResourceGroupManager::getSingleton().initialiseAllResourceGroups();
}

void OgreApplication::createScene()
{
ogreSceneManager->setAmbientLight(Ogre::ColourValue(1,1,1));

Ogre::Entity *robotEntity = ogreSceneManager->createEntity("Robot", "robot.mesh");
Ogre::SceneNode *robotNode = ogreSceneManager->getRootSceneNode()->createChildSceneNode("RobotNode");
robotNode->attachObject(robotEntity);
robotNode->yaw(Ogre::Radian(Ogre::Degree(-90)));
}
OgreWidget.h :
#ifndef OGREWIDGET_H
#define OGREWIDGET_H

#include <QtGui>
#include <Ogre.h>

class OgreWidget : public QMdiSubWindow, public Ogre::FrameListener
{
Q_OBJECT

public:
OgreWidget(QWidget *parent = 0);
~OgreWidget();
void initialise(int renderWindowId, Ogre::Root * root, Ogre::SceneManager * sceneManager);
virtual bool frameStarted(const Ogre::FrameEvent &evt);
virtual bool frameEnded(const Ogre::FrameEvent &evt);
void setCameraPosition(const Ogre::Vector3 &pos);

virtual void showEvent(QShowEvent *e);
virtual void paintEvent(QPaintEvent *e);
virtual void moveEvent(QMoveEvent *e);
virtual void resizeEvent(QResizeEvent *e);

virtual void keyPressEvent(QKeyEvent *e);
virtual void keyReleaseEvent(QKeyEvent *e);
QPaintEngine * paintEngine() const;

public slots:
void setBackgroundColor(QColor c);

signals:
void cameraPositionChanged(const Ogre::Vector3 &pos);

protected:

private:
bool mContinue;
Ogre::RenderWindow *ogreRenderWindow;
Ogre::Viewport *ogreViewport;
Ogre::Camera *ogreCamera;
Ogre::Root *ogreRoot;
Ogre::SceneManager *ogreSceneManager;

Ogre::Vector3 mDirection;
};

#endif OGREWIDGET_H
OgreWidget.cpp :
#include "OgreWidget.h"

OgreWidget::OgreWidget(QWidget *parent) :
QMdiSubWindow(parent),
ogreRenderWindow(0),
ogreViewport(0),
ogreCamera(0),
mContinue(true),
mDirection(Ogre::Vector3::ZERO)
{
setAttribute(Qt::WA_NoSystemBackground);
setAttribute(Qt::WA_NoBackground);
setAttribute(Qt::WA_PaintOnScreen);
setAttribute(Qt::WA_OpaquePaintEvent);
setMinimumSize(160,120);
setFocusPolicy(Qt::ClickFocus);
}

OgreWidget::~OgreWidget()
{
if (ogreRoot)
{
ogreRoot->detachRenderTarget(ogreRenderWindow);
}

if(ogreRenderWindow)
{
ogreRenderWindow->removeAllViewports();
}
}

void OgreWidget::initialise(int renderWindowId, Ogre::Root * root, Ogre::SceneManager * sceneManager)
{
ogreRoot = root;
ogreSceneManager = sceneManager;

Ogre::NameValuePairList viewConfig;
Ogre::String widgetHandle;
#ifdef Q_WS_WIN
widgetHandle = Ogre::StringConverter::toString((size_t)((HWND)winId()));
#else
QWidget *q_parent = dynamic_cast <QWidget *> (parent());
QX11Info xInfo = x11Info();

widgetHandle = Ogre::StringConverter::toString ((unsigned long)xInfo.display()) +
":" + Ogre::StringConverter::toString ((unsigned int)xInfo.screen()) +
":" + Ogre::StringConverter::toString ((unsigned long)q_parent->winId());
#endif
Ogre::String renderWindowIdStr = Ogre::StringConverter::toString(renderWindowId);

viewConfig["externalWindowHandle"] = widgetHandle;
ogreRenderWindow = ogreRoot->createRenderWindow("Ogre rendering window"+renderWindowIdStr,
width(), height(), false, &viewConfig);

ogreCamera = ogreSceneManager->createCamera("myCamera"+renderWindowIdStr);
ogreCamera->setPosition(0, 50,150);
ogreCamera->lookAt(0,50,0);

ogreViewport = ogreRenderWindow->addViewport(ogreCamera);
ogreViewport->setBackgroundColour(Ogre::ColourValue(1,0,0));
ogreCamera->setAspectRatio(Ogre::Real(width()) / Ogre::Real(height()));

ogreRoot->addFrameListener(this);
}

bool OgreWidget::frameStarted(const Ogre::FrameEvent& evt)
{
return mContinue;
}

bool OgreWidget::frameEnded(const Ogre::FrameEvent& evt)
{
return mContinue;
}

void OgreWidget::setBackgroundColor(QColor c)
{
if(ogreViewport)
{
Ogre::ColourValue ogreColour;
ogreColour.setAsARGB(c.rgba());
ogreViewport->setBackgroundColour(ogreColour);
}
update();
}

void OgreWidget::showEvent(QShowEvent *e)
{
QMdiSubWindow::showEvent(e);
}

void OgreWidget::paintEvent(QPaintEvent *e)
{
QMdiSubWindow::paintEvent(e);

ogreRoot->_fireFrameStarted();
ogreRenderWindow->update();
ogreRoot->_fireFrameEnded();

e->accept();
}

void OgreWidget::moveEvent(QMoveEvent *e)
{
QMdiSubWindow::moveEvent(e);

if(e->isAccepted() && ogreRenderWindow)
{
ogreRenderWindow->windowMovedOrResized();
}
update();
}

void OgreWidget::resizeEvent(QResizeEvent *e)
{
QMdiSubWindow::resizeEvent(e);

if(e->isAccepted())
{
const QSize &newSize = e->size();
if(ogreRenderWindow)
{
ogreRenderWindow->resize(newSize.width(), newSize.height());
ogreRenderWindow->windowMovedOrResized();
}
if(ogreCamera)
{
Ogre::Real aspectRatio = Ogre::Real(newSize.width()) / Ogre::Real(newSize.height());
ogreCamera->setAspectRatio(aspectRatio);
}
}
update();
}

void OgreWidget::setCameraPosition(const Ogre::Vector3 &pos)
{
ogreCamera->setPosition(pos);
ogreCamera->lookAt(0,50,0);
update();
emit cameraPositionChanged(pos);
}

void OgreWidget::keyPressEvent(QKeyEvent *e)
{
switch(e->key())
{
case Qt::Key_Escape:
mContinue = false;
break;
case Qt::Key_Z:
mDirection.z = -1;
break;
case Qt::Key_S:
mDirection.z = 1;
break;
case Qt::Key_Q:
mDirection.x = -1;
break;
case Qt::Key_D:
mDirection.x = 1;
break;
case Qt::Key_PageUp:
mDirection.y = 1;
break;
case Qt::Key_PageDown:
mDirection.y = -1;
break;
}

const Ogre::Vector3 &actualCamPos = ogreCamera->getPosition();
setCameraPosition(actualCamPos + mDirection);

e->accept();
}

void OgreWidget::keyReleaseEvent(QKeyEvent *e)
{
switch(e->key())
{
case Qt::Key_Z:
mDirection.z = 0;
break;
case Qt::Key_S:
mDirection.z = 0;
break;
case Qt::Key_Q:
mDirection.x = 0;
break;
case Qt::Key_D:
mDirection.x = 0;
break;
case Qt::Key_PageUp:
mDirection.y = 0;
break;
case Qt::Key_PageDown:
mDirection.y = 0;
break;
}

e->accept();
}

QPaintEngine * OgreWidget::paintEngine() const
{
return 0;
}