All QML apps crash with: Failed to create OpenGL context for format QSurfaceFormat

[knoxy]

Hi,

I've been learning QML and have been writing simple test programs for the last few days. This has been working fine.
Using Qt 5.9.1, Ubuntu 14.04 VBox VM.

Yesterday my simple app crashed for no apparent reason and now no QML apps will run on my system.

Any QML app, including the examples, crashes with the following:

OpenGL Warning: glXChooseVisual: bad attrib=0x186a1, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x8ea0fa0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a1, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x8ea0fa0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a1, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x8ea1000, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a1, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x186a0, ignoring
OpenGL Warning: glXChooseVisual: bad attrib=0x8ea1000, ignoring
QEGLPlatformContext: Failed to create context: 3004
Failed to create OpenGL context for format QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::SwapBehavior(DoubleBuffer), swapInterval 1, profile  QSurfaceFormat::OpenGLContextProfile(NoProfile)) 
Aborted (core dumped)

I'm stumped why things would suddenly break.

I searched online for "QML Failed to create OpenGL context for format QSurfaceFormat". There are many references to similar issues, but no clear resolution.

I've got openGL stuff (mesa) installed. glxgears and glxinfo run fine.

Any ideas what could have gone wrong?

Thanks!

[knoxy]

My "workaround" was to remove all mesa GL packages, which also removed xorg and xfce. Then I reinstalled xubuntu-desktop.

Voila! QML stuff runs again!

This is not an optimal solution. I'd like to understand why this happened so I can avoid it in the future.