Ubuntu: "QOpenGLShaderProgram shader program is not linked"

[dcortesi]

The app is written in PyQt and Qt both version 5.9. The app runs correctly on Mac OS X. (Edit: the app also runs correctly on Windows 7.) Moving the same source code to a linux system running 64-bit Ubuntu, the app displays a solid-black window and produces many multiple error sequences like:

QOpenGLShaderProgram::uniformLocation(qt_Matrix): shader program is not linked
QOpenGLShaderProgram: could not create shader program
QOpenGLShader: could not create shader
shader compilation failed: ""

There is no explicit use of OpenGL in the program, it uses just standard widgets, QMainWindow, QListView, and QWebEngineView.

How do I tell it to quit trying to use OpenGL? Is there a style setting or something I can give to QApplication?

[dcortesi]

This problem is a specific Linux problem when the local graphics drivers are NVIDIA, but the linked libGL.so is not the NVIDIA version.

This is the Ubuntu bug that explains the issue, it is 4 years old!

People on the PyQt mailing list provided this info, and suggested a simple work-around. Add the following code early in the setup of the app:

if sys.platform.startswith( 'linux' ) :
    from OpenGL import GL

The GL module will import the correct (openGL.so.1) dll. Another suggested approach was to use ctypes,

import ctypes
ctypes.cdll.LoadLibrary("libGL.so.1")

I did not try this. A third approach would be to find the system libGL.so and symlink it to libGL.so.1 however when I poked around the innards of Ubuntu 16 (64-bit) the number and links-between of the various libGL* files were more complicated than this simple idea would suggest so I did not try it.