trapezoidal distortion in X

[Lasaro Camargos]

Dear XOrg developers,

I am looking for a way to correct trapezoidal distortion due to a
projection from a projector that is not right in front of the window
it will project on. For example, the projector may be at the ceiling,
just a few feet away from the wall it is supposed to project into, or
even moving in some remotely controlled way. I would like to, given my
previous knowledge of how projector and projection screen/wall are
relatively to each other, distort the buffer in X so that the
projection is corrected. The idea is to make it work for X, not only
for my own programs, and that is why I am looking into X.

Please advise:
- have you seem similar ideas implemented anywhere else? I would love
not having to do it myself, since this is a mean not an end of my
projects.
- if you have not, how would you implement it?
- if this is an abominable idea, please explain why. I am easily convinced.

I swear to have done my homework and not found anything related to
what I need to do.

Best regards.
Lásaro