Generated texture do not update automatically with OnDemand render policy

I generate textures using Qt3DRender::QTextureImageDataGenerator. These textures can be changed interactively by manipulating some widgets. But the scene is not updated automatically, I have to click in the 3D window and maybe rotate the scene before the texture is updated.

I have attached a small example that demonstrates the problem.

Is there a workaround for forcing a few frames to be rendered until the texture is updated?