Ok, great. That works as long as you render to texture and save with
tex->createSource() instead of
copyWindowSurface(). The latter is of course limited to the max window size, which is limited by the display size.
I can’t set the window to hidden in prepareSettings, but I can set its size to 1x1, and then hide it in setup. However, this still causes the whole screen to flash momentarily black twice. It’s not the end of the world, but any idea how to fix that?