[PyQt] Errors while rendering to multiple QGLWidgets in a multi-threaded app

[David Boddie]

On Sat, 5 Nov 2011 17:57:04 -0700, Michael Broxton wrote:

> I wanted to send another quick request for help in case any PyQt devs or
> users can help me with the QGLWidget multi-threaded rendering bug I posted
> about below... I've done a little more testing this week and found that
> this issue occurs on Linux as well, so the problem does appear to be truly
> cross-platform (confirmed on Mac/Win/Linux).

The code you posted earlier crashed for me using both the Python threading
module and QThread. The OpenGL context also caused the GUI to block, so
perhaps that's a clue you can follow.

> Once again, I have a C++ 
> implementation of the test program in pure Qt that does not crash when
> rendering multiple QGLWidgets from multiple threads, so I don't think that
> my approach is fundamentally flawed.  However, the PyQt test program
> (https://gist.github.com/1318290) does crash shortly after multiple render
> threads are up and running.  Any clues as to why this is happening in PyQt
> but not pure Qt would be greatly appreciated.

I wonder if there's a race condition somewhere that lets you get away with
it in C++ but not in Python. In any case, I'd be concerned that there's some
interaction with the main thread that you're not aware of.

David