Screen is inverted with an even number of post-processing shaders

[bil-bas]

[bil-bas]

I think this is a similar effect noticed by amimeyet_ (https://gist.github.com/183ead3f0f8158e1a379)

Apparently drawing @decal before @b2 works just fine!

I really just need to "think" a bit more about what is getting flipped where, rather than just fiddling with it until it works. I actually draw everything upside down with Textures, since otherwise I need to store all the pixel data upside down instead.