You are right[1], and there won't be a single linear transform. This page curl will almost certainly be a piecewise linear approximation using a triangle mesh whose vertices are animated according to the user input.
1. The GPU will also support projective transforms - but that won't help here.
> This page curl will almost certainly be a piecewise linear approximation using a triangle mesh whose vertices are animated according to the user input.
I honestly can't tell if your being facetious here or not. There are certainly much simpler ways of pulling off this effect; ask any Demoscene participant.
Simpler in what way? Demoscene code is seldom simple to read or write, and usually doesn't take advantage of hardware acceleration. When I think demoscene, I think of getting crazy effects through esoteric bit manipulations. When you're already shipping OpenGL and your whole UI is composited with that, the easiest option is probably just texture mapping on to a low-resolution mesh.
1. The GPU will also support projective transforms - but that won't help here.