QtOpenGL | some Qt OpenGL Demo | Build Tool library

If you use Qt6, then you need to link against openglwidgets.

See https://doc.qt.io/qt-6/qopenglwidget.html

It seems that QGLWidget (which, by the way, is deprecated, and QOpenGLWidget should be used instead) doesn't implement sizeHint(), so it returns an invalid size (QSize(-1, -1)), which means that the widget can be possibly resized to a 0 width and/or height.

Since the plot widget has an expanding size policy (and dynamically reimplements sizeHint()) the result is that the gl widget is completely hidden, having 0 height.

A possible solution is to add the widgets with a proper stretch argument to the layout.

If you want both widgets to have the same height, you can do the following:

So I finally found the solution myself. From what I understand, the reason you cannot find QtWebEngine in the Raspberry Pi OS repositories, is that the Pi OS is made to run on all Raspberry Pi's, including Pi 1 and Pi 2, which have an ARMv6 and ARMv7 CPU architecture respectively. The WebEngine module however is platform dependend and not tested, compiled and distributed for ARMv6/7 anymore, so they won't release it in the repositories for Raspberry Pi OS. Luckily though, the Raspberry Pi 3 that I use has ARMv8, so it is possible to install QtWebEngine from Debian repositories, which offer QtWebEngine for exactly that architecture. Here is how:

Open your sources.list file

The things I eventually had to do were slightly more than I first thought & expected and so I decided to share the whole now-fixed example, with you:

• First I found out in the QT's Documentaion that the content of the QGLWidget module had been replaced with a new module called QtOpenGLWidgets and that many of the QMouseEvent's functions had been deprecated.
• Then that the equivalent QGLWidget's updateGL() function for the QtOpenGlWidgets was the update() ².
• QGLWidget's function bindTexture() had to be replaced with QtOpenGL.QOpenGLTexture().
• QGLWidget's qglClearColor() with glClearColor().
• and make some changes on the original example .

_{Redistributions of source code must retain the above copyright notice...}

You showed nm output for /usr/local/lib64/ libclFFT.so yet ldd says it found /lib/x86_64-linux-gnu/ libclFFT.so.2.

Set the LD_LIBRARY_PATH environment variable to /usr/local/lib64 when you run main to make sure it looks there first. Alternatively, add it to your /etc/ld.so.conf.d tree (and re-run ldconfig).

Install the OpenGL dev support:

This answer is very limited to the specific question (prevent the user to move the mouse outside the boundaries of the given widget). Unfortunately, it's not a complete solution due to many conceptual problems in the given code:

1. both drag and drop events should always be managed by the widget that will actually handle them (in this case, nodeBoardWidget), not their parent;
2. getting the layout index of an item should always consider the item geometry (using a fixed size is discouraged, since widget sizes depend on lots of aspects) and the fact that an item could not be a widget (nested layouts are still layout items, so layout.itemAt().widget() could return None);
3. "swapping" items based on item indexes doesn't always keep the item index, as the resulting indexes could be unreliable (especially for grid layouts);

The important aspect to keep in mind is that trying to move the mouse by a small and fixed amount to "fix" its position is wrong, because mouse events are not continuous: if the mouse is moved very fast from x=0 to x=100 you don't get all values between 0 and 100, but only a small fraction of the intermediate positions.
For the same reason, trying to "fix" the position just by a fixed amount of pixels is wrong, since the offset can be variable depending on the mouse speed.

The above results in dragMoveEvent not being called if the mouse moves too fast outside the parent boundaries. While in your specific case it "works", it's only because you implemented the function in the parent (which, as said, is not the suggested approach, and this is a clear example of that reason). If the mouse position has to be "contained", the dragLeaveEvent must be implemented instead.

The last parameter of glVertexPointer and glColorPointer is not the buffer object, but an offset in to the buffer objects data store.
When you call glVertexPointer or glColorPointer, the buffer currently bound to the target GL_ARRAY_BUFFER is associated to the fixed function attribute. You need to bind the proper buffer before calling glVertexPointer or glColorPointer:

You don't have to compile the GLFW source package. The precompiled binary package contains binaries for both Visual Studio and MinGW.

You have to link the OpenGL binary, so your LIBS line in the .pro file should be: