[REG 5.7->5.9.X]/Windows 32bit only(!). Qt Quick crashes "Render thread failed to start, aborting application"

Hi, 

I developped an interface between an numerical interpreter (Nelson) and QML.

https://nelson-numerical-software.github.io/nelson-website/QML_ENGINE.html

On macos x, linux 32/64 bits, arm, windows x64, all tests between QML and Nelson (https://www.youtube.com/watch?v=PSijmv8pEVA) work perfectly.

But on win32 target, when I call same code, it fails with exceptions in Qt5quick.dll

With 5.9.x, I have this problem. With 5.7 same code works also on win32 ...

Steps to reproduce this problem:

build nelson on win32 see https://github.com/Nelson-numerical-software/nelson

(https://github.com/Nelson-numerical-software/nelson/blob/master/DEVELOPMENT.md)

start Nelson (/bin/win32/nelson-gui.exe)

launch qml demos , type: qml_demos

On win32 qt 5.9.1 crashs

on win32 qt 5.7, it works

I know that i do not give an easy way to reproduce this problem ...

Thanks for your help

Allan

Qt5Quick.dll!QSGThreadedRenderLoop::handleExposure(QQuickWindow * window) Line 998
"Render thread failed to start, aborting application"