View Full Version : Getting "QWidget::releaseDC(): failed to release HDC" when using a Qt + OSG Viewer.

28th October 2013, 17:18
NOTE: I also posted this in the OSG mailing list.


I have mixed Qt and OSG to create a viewer for the PCL library OutOfCore trees (using the wrapper classes of osgpcl written by Adam Stambler: https://github.com/adasta/osgpcl).

I started with the osgQtViewer example and changed it accordingly with my needs. Using Windows 7 64 bits, the viewer works great.
Now, I tried to run the viewer in 32 bits and got an assertion error from Eigen that I could overpass including this in my class:


But then I got a new error about constructing a QWidget before a QApplication when creating the graphics context:

osg::ref_ptr<osgQt::GraphicsWindowQt> gc = new osgQt::GraphicsWindowQt(traits.get());

This was due to mixing debug and release libraries.

Now, using only release libraries I got rid of that error and the viewer widget window appears, but when it is about to show the OutOfCore tree, the app segfaults with this error:

QWidget::releaseDC(): failed to release HDC (El identificador del contexto de dispositivo (DC) no es v?lido.)

My viewer class inherits both from QWidget and from osg::CompositeViewer. Here is how the widget is called:

// The widget already exists. It is created in the main thread with some default values. No camera, no graphics context.

osg::Vec3d eye, up;

widget->getCameraManipulator()->getHomePosition(eye, center, up);

distance = widget->getCameraManipulator()->getFusionDistanceValue();

And the involved methods from the OSG+Qt Viewer:

void QOSGViewer::AddCloud(void) {

std::cout << "Loading cloud from file: " << cloud_file.c_str() << "\n";

int fileformat_idx( cloud_filepath.find(".pcd") );

std::string aux( cloud_filepath.substr(0, fileformat_idx) );

aux += "_octree/tree.oct_idx";

QWidget* widget = AddViewWidget(




qDebug() << "YAY"; // REACHES THIS

QGridLayout* grid = new QGridLayout;


grid->addWidget( widget, 0, 0 );

this->setLayout( grid );


osg::Camera* QOSGViewer::CreateCamera(

int x,

int y,

int w,

int h,

const std::string &name,

bool windowDecoration

) {

osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();

osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;

traits->windowName = name;

traits->windowDecoration = windowDecoration;

traits->x = x;

traits->y = y;

traits->width = w;

traits->height = h;

traits->doubleBuffer = true;

traits->alpha = ds->getMinimumNumAlphaBits();

traits->stencil = ds->getMinimumNumStencilBits();

traits->sampleBuffers = ds->getMultiSamples();

traits->samples = ds->getNumMultiSamples();

osg::ref_ptr<osg::Camera> camera = new osg::Camera;

// camera = new osg::Camera;

osg::ref_ptr<osgQt::GraphicsWindowQt> gc = new osgQt::GraphicsWindowQt(traits.get());

camera->setGraphicsContext( gc.get() );

camera->setClearColor( osg::Vec4(0,0,0,1) );

camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );







return camera.release();


osg::Node* QOSGViewer::ReadOctree(const std::string &file) {

osg::Group* group = new osg::Group;

group->addChild( osgDB::readNodeFile(file, options) );

return group;


QWidget* QOSGViewer::AddViewWidget(

osg::Camera *camera,

osg::Node *scene

) {

osgViewer::View* view = new osgViewer::View;

// view = new osgViewer::View;

view->setCamera( camera );

view->setSceneData( scene );

addView( view );

view->addEventHandler( new osgViewer::StatsHandler );

view->setCameraManipulator( new osgGA::TrackballManipulator );

osgQt::GraphicsWindowQt* gw = dynamic_cast<osgQt::GraphicsWindowQt*>(



return gw ? gw->getGLWidget() : 0;


Can you please tell me where I'm failing? I'm clueless about this crash.

Best regards,

6th November 2013, 16:39