Q:

Where is SDL.P (Point constructor) defined?

I've attempted to comb the repository (oh the joys of globally used single character names) without luck, but maybe I'm looking for the wrong things. 
Seeing documentation for SDL.P would probably also work. 
For future reference, is there a good way to go about finding data constructors in Haskell (as they seem to be difficult to grep for in the single-character case)?

A:

Hackage has haddocks for the sdl2 package. If you click the "Index" link, then click "P", you can find a list of all identifiers that start with that letter -- including the P data type.
http://hackage.haskell.org/package/sdl2-2.4.1.0/docs/doc-index-P.html

A:

Is this it? It’s all I could find using stackage search within the “sdl2” package.
https://www.stackage.org/haddock/lts-12.13/sdl2-2.4.1.0/SDL-Internal-Vect.html#v:P
Edit, how I did it:
You can limit the search offered by Stackage to a single package, using the URL: https://www.stackage.org/package/PACKAGE_NAME, so in this case https://www.stackage.org/package/sdl2.
Searching for operators, put them in parentheses, such as "(.)".  For your question, search for "P" like so: https://www.stackage.org/lts-12.13/hoogle?q=P&package=sdl2

