Comment 6 for bug 1374594

1) Yes, but keep in mind that CartoonInk requires texpix_txaux in the *fragment shader*, whereas HalfPixelShift requires all of the texpix inputs in the *vertex shader*.

But yes, I agree this is only a temporary solution. If we improve the design of the filter system to be more modular, I imagine that each Filter instance could 'register' a list of inputs they need for the final compositing shader.

2) The first stage, you say? These issues are only relevant to the final compositing stage, since each individual stage can specify their own shader to do the flip. Let's try not to over-engineer this too much.

As for a mirror effect, this could be done by flipping the quad on the final card, and requires no shader code. I don't see how this applies to camera-based mirrors in the scene, though, since those have to be done by flipping the camera across a plane in 3-D space.