What is this?

- This is a small piece of code, written in C++, that acts as a bridge between

a child process and the Steamworks SDK. The child process links against a

small piece of code, written in C, to facilitate communication with the

bridge.

What would I ever need this for?

- You have a GPL-licensed game and can't link directly against the Steamworks

SDK. The child process links against the simple, open source C code, which

talks to the open source C++ code via a pipe, which talks to Steamworks. You

can now add Steam achievements to your game without violating the GPL.

How does it work?

- You get a copy of the Steamworks SDK, and link steamshim_parent.cpp against

it. You ship that program and the steam_api.dll (or whatever) with your game.

- The parent process (the C++ code) gets launched as if it were your game. It

initializes Steamworks, creates some pipes and launches your actual game, then

waits on your game to talk to it over those pipes.

- Your game links against steamshim_child.c and at some point #includes

steamshim_child.h to use this functionality.

- Your game calls STEAMSHIM_init() at startup to prepare the system. It can

then make other STEAMSHIM_*() calls to interact with the parent process and

Steamworks.

- Your game, once a frame, calls STEAMSHIM_pump() until it returns NULL. Each

time it doesn't return NULL is a new message (event) from the parent process.

Often times, this is results from a command you asked the parent process to

do earlier, or some other out-of-band event from Steamworks.

- Your game, when shutting down normally, calls STEAMSHIM_deinit(), so the

parent process knows you're going away. It says goodbye, shuts down the pipe,

waits for your game to terminate, and then terminates itself.

Is this all of Steamworks?

- No! It's actually just enough to deal with stats and achievements right now,

but it can definitely be extended to offer more things. Take a look at

How do I get the Steamworks SDK?

- Go to https://partner.steamgames.com/ and login with your Steam account. You

can agree to some terms and then download the SDK.

Is there an example?

- That would be testapp.c. This example expects you to own Postal 1 on Steam and

will RESET ALL YOUR ACHIEVEMENTS, so be careful running it. But hey, if you

lose your work, it's a good exercise in SteamShim usage to put them back

again. :)

Questions? Ask me.

--ryan.

icculus@icculus.org