We have a QWidget based application that was previously using a QWindow for OpenGL rendering. To fit that window in our application we had to use
QWidget QWidget::createWindowContainer(QWindow);
Previously we only used external to Qt OpenGL libraries for rendering.
We have a desire to switch from using QWindow to some kind of QWidget for compatibility with touch gestures, and generally better overall compatibility with the rest of our application. The latest recommended OpenGL compatible QWidget seems to be QOpenGLWidget, so we are trying to use that.
glContext is an OpenGLContext that we manage ourselves.
The problem now is that QOpenGLWidget is not a QSurface, so I cannot call
glContext->makeCurrent(this);
to make the context current on my custom QOpenGLWidget like we could before with our custom QWindow and our own OpenGLContext.
If I try to use QOpenGLWidget::makeCurrent(); then this uses the wrong context and tries to do stuff with some magical QT handled context or something I don't understand.
The result is that after creating our OpenGLContext when we try to call
glFunctions = glContext->versionFunctions<QOpenGLFunctions_3_3_Core>();
if(!glFunctions->initializeOpenGLFunctions())
printf("Could not initialize OpenGL functions.");
It always fails to initialize the OpenGL functions.
I have been reading over all the other resources I can find on the subject and came across this older Stack Overflow question that was similar:
QOpenGLWidget with shared OpenGL context?
The answer to that question did not solve my issue because we are using QApplication, not QGuiApplication as this is a QWidget based application.
QGuiApplicationPrivate::init() is never called and the QOpenGLContext::globalShareContext() returns a null pointer since it is not initialized.
Unfortunately I cannot wait for QOpenGLWidget::initializeGL() to be called to initialize the QT managed OpenGLContext since we already have lots of OpenGL resources over various classes that attempt to get initialized before that.
Has anyone else come across this same problem?
Any suggestions?
I am doing a little guess work here.
Probably your OpenGL is defaulting to ANGLE.
And your previous application OpenGL calls are platform specific OpenGL API.
try setting below attribute to your QApplication object.
appObject->setAttribute(Qt::AA_UseDesktopOpenGL, true);
then try calling
QOpenGLWidget::makeCurrent();
If things are still not working, configure your QT libraries for desktop OpenGL.
configure -opengl desktop
the below link gives you some information on Qt approach to OpenGL.
http://doc.qt.io/qt-5/windows-requirements.html
Put in comments, if this is not helping you, will delete the answer.
Related
I'm creating an application, which interacts with OpenGL via QOpenGL* classes. The graphics is shown through a QOpenGLWidget, which is placed in a UI-form.
Now, there is a library for CAD purposes (Open CASCADE), an OpenGL interface of which requires a handle to the render window. The question is: can I somehow say the library to render everything to the mentioned widget?
In other words, is there a way to interpret the widget as a native, probably, platform-specific (HWND here) window, so that the library renders its own stuff exactly there?
Thanks
QOpenGLWidget is not the same thing as QGLWidget.
The classical approach for embedding OCCT 3D viewer, which you can find in Qt IESample coming with OCCT, creates QWidget with unique window handle flag, takes this window handle and ask OCCT to take care about OpenGL context creation for this window. This is most straightforward, robust and portable way with one limitation - Qt will not be able drawing semitransparent widgets on top of this QWidget. This is not a limitation of OCCT, but rather limitation of Qt Widgets design.
QOpenGLWidget was intended to solve this limitation by allowing to mix custom OpenGL rendering and normal widgets. The integration of external OpenGL graphics engine, however, became more complicated and fragile. It is not very helpful stealing winId() from QOpenGLWidget, as rendering content is expected to be drawn not into window itself, but rather into OpenGL framebufer object (FBO), created by QOpenGLWidget - see QOpenGLWidget::defaultFramebufferObject() property.
External renderer is expected to render into this FBO for proper composition of Qt widgets. Luckily, OCCT is flexible enough to allow such integration. Unluckily, such integration requires some knowledge of OpenGL, as well as its usage by Qt and OCCT.
For that, you need to ask OCCT wrapping OpenGL context already created by Qt (for that V3d_View::SetWindow() provides an optional argument of type Aspect_RenderingContext, which corresponds to HGLRC on Windows and can be fetched using wglGetCurrentContext() within rendering thread) as well as FBO created by QOpenGLWidget (for that, OCCT provides OpenGl_FrameBuffer::InitWrapper() and OpenGl_Context::SetDefaultFrameBuffer() methods, as well as OpenGl_Caps::buffersNoSwap flag to leave window buffer swapping management to Qt).
OCCT doesn't come yet with a sample using QOpenGLWidget, but you can find also qt/AndroidQt sample implementing similar thing for embedding OCCT 3D Viewer into QtQuick application.
After some investigation, I found that method QOpenGLWidget::winId() returns the correct handle. It's been found out only now, because the rendered scene disappeared immediately, leaving a black picture instead. However, when the viewport is resized, the scene returns back (and disappears again, though). Looks like Open CASCADE has problems with Qt 5 OpenGL implementation, since QGLWidget didn't have such problems, as far as I know.
Legacy QGLWidget could be integrated with rendering libraries (like SFML) by passing winId() result to the rendering library. But I can't make QOpenGLWidget work that way. After making it MainWindow's central widget I get series of warnings like QOpenGLWidget cannot be used as a native child widget. Consider setting Qt::AA_DontCreateNativeWidgetAncestors and Siblings.. Furthermore, the documentation says "QGLWidget on the other hand uses a native window and surface. (...) QOpenGLWidget avoids this by not creating a separate native window.". Can QOpenGLWidget be integrated with third party OpenGL software at all, or is it unsupported now?
You need to create a QWindow, initialize it and integrate into application with QWidget::createWindowContainer
class MyNativeWindow : QWindow
{
MyNativeWindow() : QWindow
{
setSurfaceType(QWindow::OpenGLSurface);
}
};
MyNativeWindow *nativeW = new MyNativeWindow();
QWidget *w = QWidget::createWindowContainer( nativeW );
// Use w as a simple QWidget
In some cases you don't need to use winId to get HWND. It is enough to know OpenGL context id. For custom gl context manipulation you may use QOpenGLContext class.
Be careful, because if your third party libraries will create native windows (in OS X) by themselves, you will have a lot of bugs with Qt. We are tied to fix bugs in our project. (Undockable docks, keyboard focus lost, impossibility of opening menus, errors with fullscreen etc.)
You may look at this code sample. And a custom context code sample.
We have a 3D rendering window created using GLFW and we want to use QWebkit for displaying a QWebPage inside the rendering (aka render the QWebPage to an OpenGL texture). Using only the CPU version is too slow and Qt supports rendering QWebkit into QOpenGLFramebufferObjects (using QOpenGLPaintDevice).
However, doing so requires the creation of a QOpenGLContext (which requires its own window and so on), eventually interfering with our whole application. (Switching between GLFW and Qt Context also causes an infinite amount of GL_INVALID_OPERATIONs)
Best case solution: we get Qt to use the GLFW Context.
Code example:
QOpenGLFramebufferObject qfbo(mWidth, mHeight); //< this crashes because he will implicitly try to get QOpenGLFunctions which gets the default context which is null
qfbo.bind();
QOpenGLPaintDevice paintdev(mWidth, mHeight);
QPainter painter(&paintdev);
painter.beginNativePainting();
mPage->mainFrame()->render( &painter );
painter.endNativePainting();
So here are some questions:
is it possible to get Qt to use the GLFW OpenGL context?
if not, how can we switch between GLFW context and Qt context? (using texture sharing for transferring the rendered QWebPage)
if all of this is impossible, is there a free Webkit project with 64bit, Windows/Linux/Mac support that can render using OpenGL?
#Sebastian Cabot wrote:
You can't directly mix the two context objects using QT. QT is great but in order to keep itself portable it also has some limitations - mainly accessing the low level handles of the objects and manipulating them directly. So Even trying to use a QOpenGLContext from a different thread then the one it was created in will fail. And in order to use any of the QT OpenGL wrappers you will need a valid QOpenGLContext current. So what you want is not possible without hacking into the QT implementation.
I'm trying to develop a cross platform (or at least desktop + embedded hardware) application. I would like to use Qt Quick to create a touch friendly GUI. I have been implemented a classical application with a QGLWidget displaying data. It is important that only a part of the window is in OpenGL. Because of this there are problems with EGLFS and LinuxFB. Only X11 (or maybe Wayland) can display the application properly (others generates a couple of errors about missing setParent function and the whole screen is black). Now I'm trying to achieve the same thing in QML. I want to use this OpenGL renderer as part of my QML application and some Qt Quick widgets around it. I found a couple of people asking about the same thing and the answer is always to subclass QDeclarativeItem and call the painter's beginNativePainting() (the others says to export it through QDeclarativeItem, but I cannot figure out how to do this). The problem is that on desktop, Qt 5.11 the native painter is not OpenGL. And in QT5 there is no way to force OpenGL graphics system. So when I try to get the OpenGL context (QGLContext::currentContext()) I always get NULL. Another problem: If I export my widget with qmlRegisterType("Test", 1, 0, "Test"); it becomes only visible when I use QDeclarativeView, but then it doesn't sees Qt Quick. If I use QQuickView it says module "Test" is not installed. How can I implement this properly?
QDeclarativeItem is from Qt Quick 1 and Qt4. With Qt 5 and Qt Quick 2 you should use QQuickItem.
There is at least 1 example of this provided with qt docs, which you can find in Qt Creator in the Welcome tab in the Examples section.
What exactly are my options? I have programs I need to write in OpenGL and DirectX, and I'd like to use Qt for OpenGL, and not have to re-implement half my program for the DirectX components of my task.
I've looked on Google and I have found references to people complaining about Direct3D being a dependency of Qt, and people talking about implementing QD3DWidget sub-classing QWidget in a similar fashion to QGLWidget, yet nobody talked about how to implement it or where any examples are.
I need help. I want to know if it is possible? What would I need to do to get it working? Has it been done before?
its pretty straightforward than I thought,
-> Create a QWidget
-> Override paintEngine() method, does nothing, just returns NULL
-> Assign HWND to widget->winId()
#ifdef USE_QTGUI
QApplication a(argc, argv);
CD3DWidget wndw; wndw.show(); wndw.resize(1280,960);
hWnd = wndw.winId();
#else
hWnd = CreateAppWindow(name,300,300);
#endif
//CD3DWidget class contains only the following definitions
CD3DWidget::CD3DWidget(QWidget * parent):QWidget(parent){ }
QPaintEngine *CD3DWidget::paintEngine (){ return NULL; }
Thanks,
CV
List of changes:
Qt 4.6 introduces many new features and improvements as well as bugfixes
over the 4.5.x series.
......................
The experimental Direct3D paint engine has been removed. The reason for
this is that Nokia focuses on OpenGL for desktop hardware accelerated
rendering.
......................
For all its worth, here is how to get Ogre3D's output to a Qt 4.5 window. Basically, you grab a rendering surface and you use it to render the output. This is a "Qt in D3D/OpenGL application approach".
Here are OpenGL examples with Qt 4.5 using OpenGL window.
If I understand it correctly, the Direct3D support is experimental and is only used for painting of windows.