So I’ve not used the ‘experimental’ package in RetroPie for Limelight (old version of moonlight, written in Java) but I have got Moonlight working and streaming Steam. I’ve configured it all so I don’t need a keyboard for anything. Its not too difficult and allows you to play Steam games as well as Dolphin (via Steam). Perhaps people don’t realise the potential of this or others like me are using it but it seems to me you could use it to literally stream anything (any consoles that don’t work).

So what you need:
* PC and Pi2 connected to Internet
* PC must have Nvidia GFE compatible GFX card (see http://shield.nvidia.com/game-stream)
* Some Linux skills (or for RetroPie to streamline this completely :D)

First you need to make and install Moonlight:
* Follow instructions on instructables tutorial
** Make sure when you get from Git you get the most up to date version, I have 2.0.1 but there may now be a newer version.
** I installed to /opt/retropie/emulators/moonlight/moonlight-embedded-2.0.1.

Once installed, make your PC have a static Local IP. This means you will never have to enter the IP when connecting from your PC.
* Follow instructions.
* NOTE: Take note of the IP you use! I am using 192.168.0.6 but use whatever you want.

Now you can check it works
* Make sure Nvidia GFE is on and go to Preferences -> GameStream and make sure that ‘On my network’ is selected.
* Go to your pi and run the following command:
moonlight pair <IP HERE>

You will have to enter an input code on the PC. Once this is done, run the following:
moonlight stream <IP HERE> -app Steam

This should show you the Big Picture Steam interface. Congrats it is connected.

Exit and create a Moonlight mapping file:

cd /opt/retropie/configs
mkdir moonlight
cd moonlight
moonlight -mapping xbox.map
<run through the instruction here>

Now to get it into emulationstation. run sudo nano /etc/emulationstation/es_system.cfg

Add the following to your systems list:

<system>
    <fullname>Steam</fullname>
    <name>Steam</name>
    <path>~/RetroPie/roms/moonlight</path>
    <extension>.steam</extension>
    <command>cd /opt/retropie/configs/moonlight; moonlight stream <IP HERE> -mapping xbox.map -app Steam
    <platform>steam</platform>
    <theme>steam</theme>
  </system>

Notice some ‘roms’ path. Well I intended to make fiels with IP addresses in them hence why that exists. There are some files that end up in there though so:

mkdir /RetroPie/roms/moonlight
touch <PCNAMEHERE>.steam

Now I also have some theme stuff I made and a gamelist.xml but you shouldn’t need it. Restart and emulationstation will have Steam. Select it and select your fake game. It should launch the Steam UI.

STEAM settings:
Go to File-Settings->In-Home Streaming in Steam:
* Enable streaming is checked
* Client options: Fast (choose whatever you want, depends on network connection)
Advanced Client Options:
* Enable hardware decoding: true
* Resolution: Desktop resolution

Get Dolphin into Steam:
This isn’t too difficult, instructions on dolphin forum, THIRD post

WARNING:
I have found that the games path (not the emulator) shouldn’t contain spaces. I suspect some odd problem between Linux/Windows file paths but not sure what is actually happening. You will get some problem like “unknown argument: Files” for example if you put the games in c:\Program Files. Obviously in Linux you would just escape the space, but the path is in a windows format (as it works on the PC) so I fixed this by having no spaces. This includes the game files!

Dolphin settings:
* Graphics Settings:
** Render to main window: TRUE (IF you forget this, your performance will be TERRIBLE)
** Backend: OpenGL (supposedly :/)
** Fullscreen Resolution: Auto
** Show FPS: true (for checking FPS is sane)
* Enhancements
** Internal Resolution: Auto
** Anti-Aliasing: None
** Antisotropic filtering: 16x
* Hacks
** Skip EFB Access: true
** Ignore format changes: true
** Store EFB Copies to Texture Only: true

Then configure your controllers as you normally do.

IF you have any issues, apologies, just post :P You can perhaps use Limelight instead of Moonlight. Moonlight is written in C though so is possibly more performance and I have not had many issues.

Games I have personally had working: Smash bros melee/brawl (3 player), mario tennis (3 player), towerfall ascension (4 player), I Zombie (little indie game), Borderlands, Orcs Must Die 2, Mark of the Ninja, Dungeon Defenders, Bioshock, Castle Crashers.

You should check Moonlight game compatibility as well. I would also:
* Backup the /etc/emulationstation/es_system.cfg and make sure it is correct especially if you are running emulationstation from boot.
* Make sure Dolphin is working on your steam BEFORE you bother testing it through the Pi so you know the steam commands are right.

I’m assuming RetroPie will upgrade the limelight to moonlight soon. I may just upgrade the scripts if I can do merge requests to get it moving.

Do not try if:
* Your linux skills aren’t very good (as its not streamlined)
* You don’t own any compatible games at all
* Your gfx card is not good enough to even do this.

Enjoy!

P.S. I have tried to include literally everything I have done for this to work for me. I may have missed something though or it may not be clear so apologies if that is the case