The DLL Project

[pd]

Are MasterKey and PrintDebugInfo wholly new routines, or do they replace pre-existing routines?

They're inside a DLL, ie not even in gamemd.exe, ie wholly new routines.
While you might point out "it replaces that command." from my previous post, that replacement I did on purpose to disable showing the mouse coords.

how does the game know when to call them?

The game does not know, my Debugger does.
Every DLL will come with a control INI file, holding information about what DLL function to call when (ie when the game reaches a specified part of code).
If it reaches one, the Debugger makes gamemd.exe jump to a special piece of code I inserted, attaching the desired DLL to it and calling the desired function.
After that's finished, it will return to where it came from (unless you modify the place to return to using SET_RETURN_EIP).

I will release a long list of code places so you have plenty of options to hook your code.
Giving you new places will stay my job, as that requires exe research like before.