[vtkusers] Qt5/VTK application does not start correctly (with X11 forwarding)

[Sophonet]

Hi list,

an application using VTK 8.0.0 and Qt 5.9.1 (built with -opengl desktop) 
does not start correctly (using X11 forwarding). After displaying an 
error message "failed to get the current screen resources", there is 
another error message

vtkXOpenGLRenderWindow (0x55f891d77a80): GL version 2.1 with the 
gpu_shader4 extension is not supported by your graphics driver but is 
required for the new OpenGL rendering backend. Please update your OpenGL 
driver. If you are using Mesa please make sure you have version 10.6.5 
or later and make sure your driver in Mesa supports OpenGL 3.2.

However, my Ubuntu 17.04 system has Mesa 17.0.7, glxgears works fine 
(using X11 forwarding) and glxinfo shows (among other things) the 
correct driver - see below, so I am a bit puzzled what is going on. Any 
hints?

Thanks,

sophonet

P.S.: The first call in my application's main() function is 
QSurfaceFormat::setDefaultFormat, see below. The same application runs 
fine and without problems on Windows.

#if QT_VERSION >= 0x050500
         // before initializing QApplication, set the default surface 
format, see documentation
         
QSurfaceFormat::setDefaultFormat(QVTKOpenGLWidget::defaultFormat());
#endif



GLX version: 1.2
GLX extensions:
     GLX_ARB_get_proc_address, GLX_ARB_multisample, 
GLX_EXT_import_context,
     GLX_EXT_visual_info, GLX_EXT_visual_rating,
     GLX_MESA_multithread_makecurrent, GLX_MESA_query_renderer,
     GLX_OML_swap_method, GLX_SGIS_multisample, GLX_SGIX_fbconfig,
     GLX_SGI_make_current_read
Extended renderer info (GLX_MESA_query_renderer):
     Vendor: VMware, Inc. (0xffffffff)
     Device: llvmpipe (LLVM 4.0, 128 bits) (0xffffffff)
     Version: 17.0.7
     Accelerated: no
     Video memory: 3949MB
     Unified memory: no
     Preferred profile: core (0x1)
     Max core profile version: 3.3
     Max compat profile version: 3.0
     Max GLES1 profile version: 1.1
     Max GLES[23] profile version: 3.0
OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 4.0, 128 bits)
OpenGL version string: 3.0 Mesa 17.0.7
OpenGL shading language version string: 1.30