Reverse engineering and fixing a DirectX game?

Question

Background

I play Imperishable Night, one of the Touhou series of games. The shoot button is “z,” the slower motion is “shift,” and the arrows move. Unfortunately for me, using the ghosts of shift-z, the arrow is to the right, so I can not move to the right while shooting. This halo occurs in all applications, and the keyboard replaces it.

goal

I want to find in the disassembled code a directx function that receives keyboard input and compares it with the key "z", and changes that key to "a". I am considering this fun project. Assuming the size of the scan codes is the same, this should be fairly simple. And since the executable file is only 400 thousand, Perhaps this will provide me with a unique opportunity to study the dark side of the computing world (just kidding).

Relevant experience

I have experience with coding in an assembly, but not in disassembling it. I have no experience with DirectX apis.

Question

I need a guide. I found a list of directx keyboard scan codes and a PEExplorer program that looks like it will do what I need.

Is there a way I can turn a part of an assembly with calls to a C function to make it easier to read? I need to find where the game retrieves the current pressed keys, compares them with a list, and this is the list I need to change.

Any input is appreciated.

Answer 1

You may be interested in the Detours library from Microsoft Research; it allows you to intercept a function that calls and changes its arguments. Executing this code can change the key scan codes of keys that are not called to those that the game expects.