Z Fighting issue with transparent window ontop of an OpenGL Application

[qtd1d1]

Hi,

I am having an issue with Z-Fighting when I put my Qt-Application, which has no frame and is transparent, ontop of an simple OpenGl Application (triangle example).
Does anybody know how to fix this issue?

The only thing I found is to use following line to make the used OpenGL variables invariant:
#pragma STDGL invariant(all)

But this line doesn't solve my issue.

Thanks