ES-DE/INSTALL.md

EmulationStation Desktop Edition - Installation and configuration
=================================================================

**Note:** This is a quite technical document intended for those that are interested in compiling EmulationStation from source code, or would like to customize the configuration. If you just want to start using the software, check out the [User Guide](USERGUIDE.md) instead.


### Development Environment

EmulationStation-DE is developed and compiled using both Clang/LLVM and GCC on Unix, and GCC (MinGW) on Windows. I'm intending to get Clang/LLVM working on Windows as well.

There are much more details regarding compilers later in this document, so read on!

Any code editor can be used of course, but I recommend [VSCodium](https://vscodium.com) or [VSCode](https://code.visualstudio.com).


### Building on Unix:

The code has a few dependencies. For building, you'll need CMake and development packages for cURL, FreeImage, FreeType, libVLC, pugixml, SDL2 and RapidJSON.

**On Debian/Ubuntu:**
All of the required packages can be easily installed with `apt-get`:
```
sudo apt-get install build-essential cmake libsdl2-dev libfreeimage-dev libfreetype6-dev libcurl4-openssl-dev libpugixml-dev rapidjson-dev libasound2-dev libvlc-dev libgl1-mesa-dev
```

**On Fedora:**
For this operating system, use `dnf` (with rpmfusion activated) :
```
sudo dnf install cmake SDL2-devel freeimage-devel freetype-devel curl-devel rapidjson-devel alsa-lib-devel vlc-devel mesa-libGL-devel
```

**Cloning and compiling:**

To clone the source repository, run the following:

```
git clone https://gitlab.com/leonstyhre/emulationstation-de
```

Then generate the Makefile and build the software:

```
cd emulationstation-de
cmake .
make
```

Note: To generate a `Debug` build on Unix/Linux, run this instead:
```
cmake -DCMAKE_BUILD_TYPE=Debug .
make
```
Keep in mind though that a debug version will be much slower due to all compiler optimizations being disabled.

To build with CEC support, add the corresponding option, for example:

```
cmake -DCMAKE_BUILD_TYPE=Debug -DCEC=on .
make
```
I have however not been able to test the CEC support and I'm not entirely sure how it's supposed to work.

Running multiple compile jobs in parallel is a good thing as it speeds up the build time a lot (scaling almost linearly). Here's an example telling make to run 6 parallel jobs:

```
make -j6
```

By default EmulationStation will install under `/usr/local` but this can be changed by setting the `CMAKE_INSTALL_PREFIX` variable.\
The following example will build the application for installtion under `/opt`:

```
cmake -DCMAKE_INSTALL_PREFIX=/opt .
```

It's important to know that this is not only the directory used by the install script, the CMAKE_INSTALL_PREFIX variable also modifies code inside ES used to locate the required program resources. So it's necessary that the install prefix corresponds to the location where the application will actually be installed.

**Compilers:**

Both Clang/LLVM and GCC work fine for building ES.

I did some small benchmarks comparing Clang to GCC with the ES codebase (as of writing it's year 2020) and it's pretty interesting.

Advantages with Clang (vs GCC):
* 10% smaller binary size for a release build
* 17% smaller binary size for a debug build
* 2% faster compile time for a release build
* 16% faster compile time for a debug build
* 4% faster application startup time for a debug build

Advantage with GCC (vs Clang):
* 1% faster application startup time for a release build

*Release build: Optimizations enabled, debug info disabled, binary stripped.* \
*Debug build: Optimizations disabled, debug info enabled, binary not stripped.*

This Clang debug build is LLVM "native", i.e. intended to be debugged using the LLVM project debugger LLDB. The problem is that this is still not well integrated with VSCodium that I use for development so I need to keep using GDB. But this is problematic as the libstd++ data required by GDB is missing in the binary, making it impossible to see the values of for instance `std::string` variables.

It's possible to activate the additional debug info needed by GDB by using the flag `-D_GLIBCXX_DEBUG`. I've added this to CMakeLists.txt when using Clang, but this bloats the binary and makes the code much slower. Actually, instead of a 4% faster application startup, it's now 36% slower! The same goes for the binary size, instead of 17% smaller it's now 17% larger.

I'm expecting this to be resolved in the near future though, and as I think Clang is an interesting compiler, I use it as the default when working on the project (I sometimes test with GCC to make sure that it still builds the software correctly).

It's by the way very easy to switch between LLVM and GCC using Ubuntu, just use the `update-alternatives` command:

```
user@computer:~$ sudo update-alternatives --config c++
[sudo] password for user:
There are 2 choices for the alternative c++ (providing /usr/bin/c++).

  Selection    Path              Priority   Status
------------------------------------------------------------
* 0            /usr/bin/g++       20        auto mode
  1            /usr/bin/clang++   10        manual mode
  2            /usr/bin/g++       20        manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/clang++ to provide /usr/bin/c++ (c++) in manual mode
```

Following this, just re-run cmake and make and the binary should be built by Clang instead.

**Installing:**

Installing the software requires root permissions, the following command will install all the required application files:

```
sudo make install
```

Assuming the default installation prefix `/usr/local` has been used, this is the directory structure for the installation:

```
/usr/local/bin/emulationstation
/usr/local/man/man6/emulationstation.6.gz
/usr/local/share/applications/emulationstation.desktop
/usr/local/share/emulationstation/LICENSE
/usr/local/share/emulationstation/LICENSES/*
/usr/local/share/emulationstation/resources/*
/usr/local/share/emulationstation/themes/*
/usr/local/share/pixmaps/emulationstation.svg
```

ES will look in the following locations for the resources, in the listed order:

* `[HOME]/.emulationstation/resources/`
* `[INSTALL PREFIX]/share/emulationstation/resources/`
* `[ES EXECUTABLE DIRECTORY]/resources/`

**Note:** The resources directory is critical, without it the application won't start.

And it will look in the following locations for the themes, also in the listed order:

* `[HOME]/.emulationstation/themes/`
* `[INSTALL PREFIX]/share/emulationstation/themes/`
* `[ES EXECUTABLE DIRECTORY]/themes/`

The theme is not mandatory to start the application, but ES will be basically useless without it.

So the home directory will always take precedence, and any resources or themes located there will override the ones in the installation path or the path of the ES executable.

**Creating .deb and .rpm packages:**

Creation of Debian .deb packages is enabled by default, simply run `cpack` to generate the package:

```
user@computer:~/emulationstation-de$ cpack
CPack: Create package using DEB
CPack: Install projects
CPack: - Run preinstall target for: emulationstation-de
CPack: - Install project: emulationstation-de []
CPack: Create package
CPackDeb: - Generating dependency list
CPack: - package: /home/user/emulationstation-de/emulationstation-de-1.0.0.deb generated.
```

The package can now be installed using a package manager, for example `dpkg`.

For RPM packages, change the comments in the `CMakeLists.txt` accordingly, from:

```
#SET(CPACK_GENERATOR "RPM")
SET(CPACK_GENERATOR "DEB")
```
to:
```
SET(CPACK_GENERATOR "RPM")
#SET(CPACK_GENERATOR "DEB")
```

Then simply run `cpack`.

To be able to generate RPM packages on a Debian system such as Ubuntu, install the `rpm` package first:

```
sudo apt-get install rpm
```


### Building on Windows:

This is a strange legacy operating system. However it's still popular, so we need to support it.

I did a brief evaluation of the Microsoft Visual C++ compiler (MSVC) but as far as I'm concerned it's an abomination so I won't cover it here and it won't be supported.

At the moment I have only built the software using GCC on Windows, but I aim to get Clang/LLVM working at a later date.

Anyway, here's a brief summary of how to get a build environment up and running on Windows.

**Install Git, CMake, MinGW and your code editor:**

[Git](https://gitforwindows.org)

[CMake](https://cmake.org/download)

[MinGW](https://gnutoolchains.com/mingw64)

Make a copy of `mingw64/bin/mingw32-make` to `make` just for convenience and make sure that the necessary paths are defined for the PATH environmental variable.

I won't get into the details on how to configure Git, but there are many resources available online to support with this. The `Git Bash` shell is very useful though as it's somewhat reproducing a Unix environment using MinGW/MSYS.

Install your editor of choice. As for VSCodium it's unfortunately broken or crippled under Windows, making some important extensions impossible to install. VSCode can however be used instead.

It's strongly recommended to set line breaks to Unix-style (linefeed only) directly in the editor, although it can also be configured in Git for conversion during commit. The source code for EmulationStation-DE only uses Unix-style line breaks.

**Enable pretty printing for GDB:**

This is useful for displaying `std::string` values for example.

Adjust your paths accordingly, the below are just examples of course.

Save a file to
C:/Programming/mingw64/bin/pp.gdb with the following contents:

```
python
import sys
sys.path.insert(0, 'c:/Programming/mingw64/share/gcc-9.1.0/python/libstdcxx/v6')
from printers import register_libstdcxx_printers
register_libstdcxx_printers (None)
end
```

If using VSCode, add the following line to launch.json:

`"miDebuggerArgs": "-x c:/programming/mingw64/bin/pp.gdb",`

An equivalent setup should be possible on other code editors as well.

Note that most GDB builds for Windows have broken Python support so that pretty printing won't work. The MinGW installation recommended in the previous step works fine though.

**Download the dependency packages:**

[FreeImage](https://sourceforge.net/projects/freeimage)

[cURL](https://curl.haxx.se/download.html)

[SDL2](https://www.libsdl.org/download-2.0.php)

[libVLC](https://ftp.lysator.liu.se/pub/videolan/vlc)

Uncompress the files to a suitable directory, for example C:/Programming/Dependencies/

The following packages are not readily available for Windows, so clone the repos and build them yourself:

[FreeType](https://www.freetype.org)
```
git clone git://git.savannah.gnu.org/freetype/freetype2.git
git checkout VER-2-10-2
mkdir build
cmake -G "MinGW Makefiles" -DBUILD_SHARED_LIBS=ON ..
make
```

[pugixml](https://pugixml.org)
```
git clone git://github.com/zeux/pugixml
git checkout v1.10
cmake -G "MinGW Makefiles" -DBUILD_SHARED_LIBS=ON .
make
```

As for RapidJSON, you don't need to compile it, you just need the include files:

[RapidJSON](http://rapidjson.org)
```
git clone git://github.com/Tencent/rapidjson
git checkout v1.1.0
```

**Clone the EmulationStation-DE repository:**

This works the same as in Unix, just run the following:

```
git clone https://gitlab.com/leonstyhre/emulationstation-de
```

**Setup the include directories:**

As there is no standardized include directory structure in Windows and no package manager, you need to provide the include files manually.

Make a directory in your build environment tree, for instance under `C:/Programming/include`.

Copy the include files from cURL, FreeImage, FreeType, pugixml, RapidJSON, SDL2 and VLC to this directory.
It should then look something like this:

```
$ ls -1 include/
curl/
FreeImage.h
freetype/
ft2build.h
pugiconfig.hpp
pugixml.hpp
rapidjson/
SDL2/
vlc/
```

**Copy the required DLL files to the EmulationStation build directory:**

As there's no package manager in Windows and no way to handle dependencies, we need to ship all the required shared libraries with the application.

Copy the following files to the `emulationstation-de` build directory. Most of them will come from the packages that were provided in the previous steps of this guide:

```
FreeImage.dll
libcrypto-1_1-x64.dll    (from the OpenSSL package, located in Git MinGW/MSYS under /mingw/bin/)
libcurl-x64.dll
libfreetype.dll
libgcc_s_seh-1.dll    (located in Git MinGW/MSYS under /mingw/bin/)
libpugixml.dll
libssl-1_1-x64.dll    (from the OpenSSL package, located in Git MinGW under /mingw/bin/)
libstdc++-6.dll
libvlc.dll
libvlccore.dll
libwinpthread-1.dll    (located in Git MinGW under /mingw/bin/)
SDL2.dll
libSDL2main.a
```

The files from the MinGW installation must correspond to the version used to compile the binary.

*So if the MinGW installation is upgraded to a newer version or so, make sure to copy the .dll files again, overwriting the old ones.*

In addition to these, you need to copy some libraries from the VLC `plugins` folder to be able to play video files. There is a subdirectory structure under the plugins folder and although there is no requirement to retain these as libVLC apparently looks recursively for the required .dll files, it still makes it a bit more tidy to keep the folder names for each type of plugin. The CMake install script will however copy all the contents of this plugins folder regardless of whether subdirectories are in use or not.

It's a bit tricky to know which libraries are really needed. But as the plugins directory is around 120 MB (as of VLC version 3.0.11), we definitely only want to copy the files we need.

The following files seem to be required to play most video and audio formats (place them in `emulationstation-de\plugins\`):

```
access\libfilesystem_plugin.dll
audio_filter\libaudio_format_plugin.dll
audio_filter\libtrivial_channel_mixer_plugin.dll
audio_output\libwaveout_plugin.dll
codec\libavcodec_plugin.dll
codec\libx264_plugin.dll
codec\libx265_plugin.dll
logger\libconsole_logger_plugin.dll
text_renderer\libfreetype_plugin.dll
video_chroma\libswscale_plugin.dll
video_output\libvmem_plugin.dll
```

The combined size of these files is around 24 MB which is more reasonable.

**Building the application:**

For a release build:

```
cmake -G "MinGW Makefiles" -DWIN32_INCLUDE_DIR=../include .
```

Or for a debug build:

```
cmake -G "MinGW Makefiles" -DWIN32_INCLUDE_DIR=../include -DCMAKE_BUILD_TYPE=Debug .
```

For some reason defining the '../include' path doesn't work when running CMake from PowerShell (and no, changing to backslash doesn't help). Instead use Bash, by running from a `Git Bash` shell.

The make command works fine directly in PowerShell though so it can be run from the VSCode terminal.

Running `make -j6` (or whatever number of parallel jobs you prefer) should now build the binary.

Note that compilation time is much longer than on Unix, and linking time is excessive for a debug build. The debug binary is also much larger than on Unix.

A worthwhile endeavour could be to setup a cross-compilation environment using WLS/WLS2 (Linux), but I have not tried it.

**Creating an NSIS installer:**

To create an NSIS installer (Nullsoft Scriptable Install System) you need to first install the NSIS creation tool:

[NSIS](https://nsis.sourceforge.io/Download)

Simply install the application using it's installer.

After the installation has been completed, go to the emulationstation-de directory and run cpack to generate the NSIS installer:

```
$ cpack
CPack: Create package using NSIS
CPack: Install projects
CPack: - Run preinstall target for: emulationstation-de
CPack: - Install project: emulationstation-de []
CPack: Create package
CPack: - package: C:/Programming/emulationstation-de/emulationstation-de-1.0.0-win64.exe generated.
```

The default installation directory suggested by the installer is `C:\Program Files\EmulationStation`. However this can of course be changed by the user.

ES will look in the following locations for the resources, in the listed order:

* `[HOME]\.emulationstation\resources\`
* `[ES EXECUTABLE DIRECTORY]\resources\`

**Note:** The resources directory is critical, without it the application won't start.

And it will look in the following locations for the themes, also in the listed order:

* `[HOME]\.emulationstation\themes\`
* `[ES EXECUTABLE DIRECTORY]\themes\`

The theme is not mandatory to start the application, but ES will be basically useless without it.

So the home directory will always take precedence, and any resources or themes located there will override the ones in the path of the ES executable.

**Setting up a portable installation:**

It's possible to easily create a portable installation of ES for Windows, for example on a USB memory stick.

For the sake of this example, let's assume that the removable media has the device name `f:\`.

* Copy the EmulationStation installation directory to f:\
* Create the directory `ES-Home` directly under f:\
* Copy your game ROMs into `f:\ES-Home\ROMs`
* Copy your emulators to f:\ (such as the RetroArch directory)
* Create the file `start_es.bat` directly under f:\

Add the following lines to the start_es.bat file:
```
@echo off
EmulationStation\emulationstation.exe --home %CD:~0,3%ES-Home
```

The contents of f:\ should now look something like this:
```
EmulationStation
ES-Home
RetroArch
start_es.bat

```

Now run the batch script, ES should start and ask you to configure any attached controllers. Following this, check that everything works as expected, i.e. the gamelists are properly populated etc.

You can optionally skip the configuration of the controllers by copying any existing `es_input.cfg` file to `f:\ES-Home\.emulationstation\es_input.cfg`.

Exit ES and modify the file `f:\ES-Home\.emulationstation\es_systems.cfg` to point to the emulators on the portable media.

Example change, from this:
```
<command>retroarch.exe -L "%EMUPATH%\cores\snes9x_libretro.dll" %ROM%</command>
```

To this:
```
<command>%ESPATH%\..\RetroArch\retroarch.exe -L "%EMUPATH%\cores\snes9x_libretro.dll" %ROM%</command>
```

The %ESPATH% variable is explained later in this document.

Following this, optionally copy any existing gamelists and game media files to the removable media. By default these files should be located here:

`f:\ES-Home\.emulationstation\gamelists\` \
`f:\ES-Home\.emulationstation\downloaded_media\`

You now have a fully functional portable emulator installation!

The portable installation works exactly as a normal installation, i.e. you can use the built-in scraper, edit metadata etc.


Configuring EmulationStation-DE
===============================


**~/.emulationstation/es_systems.cfg:**

EmulationStation Desktop Edition ships with a comprehensive `es_systems.cfg` configuration file, and as the logic is to use a `%ROMPATH%` variable to locate the ROM files (with a corresponding setting in `es_settings.cfg`), normally you shouldn't need to modify this file to the same extent as previous versions of EmulationStation. Still, see below in this document on how to adjust the es_systems.cfg file if required.

Upon first startup of the application, if there is no es_systems.cfg file present, it will be copied from the template subdirectory inside the resources directory. This directory is located in the installation path of the application, for instance `/usr/local/share/emulationstation/resources/templates`.

The template file will be copied to `~/.emulationstation/es_systems.cfg`. \
`~` is `$HOME` on Linux, and `%HOMEPATH%` on Windows.

**~/.emulationstation/es_settings.cfg:**

When ES is first run, a configuration file will be created as `~/.emulationstation/es_settings.cfg`.

This file contains all the settings supported by ES, at their default values. Normally you shouldn't need to modify this file manually, instead you should be able to use the menu inside ES to update all the necessary settings.

The exception would be the ROMDirectory setting as ES won't start if no ROM files are found.

**Setting the ROM directory:**

By default, ES looks in `~/ROMs` for the ROM files, where they are expected to be grouped into directories corresponding to the game systems, for example:

```
user@computer:~ROMs$ ls -1
arcade
megadrive
pcengine
```

However, if you've saved your ROMs to another directory, you need to configure the ROMDirectory setting in es_settings.cfg.\
Here's an example:

`<string name="ROMDirectory" value="~/games/roms" />`

Keep in mind though that you still need to group the ROMs into directories corresponding to the platform names in es_systems.cfg.

There is also support to add the variable %ESPATH% to the ROM directory setting, this will expand to the path where the ES executable is started from. This is useful for a portable emulator installation, for example on a USB memory stick.

Here is such an example:

`<string name="ROMDirectory" value="%ESPATH%/../roms" />`

**Keep in mind that you have to set up your emulator separately from EmulationStation!**

**~/.emulationstation/es_input.cfg:**

When you first start EmulationStation, you will be prompted to configure an input device. The process is thus:

1. Hold a button on the device you want to configure.  This includes the keyboard.

2. Press the buttons as they appear in the list.  Some inputs can be skipped by holding any button down for a few seconds (e.g. page up/page down).

3. You can review your mappings by pressing up and down, making any changes by pressing A.

4. Choose "SAVE" to save this device and close the input configuration screen.

The new configuration will be added to the `~/.emulationstation/es_input.cfg` file.

**Both new and old devices can be (re)configured at any time by pressing the Start button and choosing "CONFIGURE INPUT".**  From here, you may unplug the device you used to open the menu and plug in a new one, if necessary.  New devices will be appended to the existing input configuration file, so your old devices will retain their configuration.

**If your controller stops working, you can delete the `~/.emulationstation/es_input.cfg` file to make the input configuration screen re-appear on the next run.**


Command line arguments
======================

You can use `--help` or `-h` to view a list of command line options, as shown here.

### Unix:

```
--resolution [width] [height]   Try to force a particular resolution
--gamelist-only                 Skip automatic game ROM search, only read from gamelist.xml
--ignore-gamelist               Ignore the gamelist files (useful for troubleshooting)
--show-hidden-files             Show hidden files and folders
--show-hidden-games             Show hidden games
--draw-framerate                Display the framerate
--no-exit                       Don't show the exit option in the menu
--no-splash                     Don't show the splash screen
--debug                         Print debug information
--windowed                      Windowed mode, should be combined with --resolution
--fullscreen-normal             Normal fullscreen mode
--fullscreen-borderless         Borderless fullscreen mode (always on top)
--vsync [1/on or 0/off]         Turn vsync on or off (default is on)
--max-vram [size]               Max VRAM to use in Mb before swapping
                                Set to at least 20 to avoid unpredictable behavior
--force-full                    Force the UI mode to Full
--force-kid                     Force the UI mode to Kid
--force-kiosk                   Force the UI mode to Kiosk
--force-disable-filters         Force the UI to ignore applied filters in gamelist
--home [path]                   Directory to use as home path
--version, -v                   Displays version information
--help, -h                      Summon a sentient, angry tuba
```

### Windows:

```
--resolution [width] [height]   Try to force a particular resolution
--gamelist-only                 Skip automatic game ROM search, only read from gamelist.xml
--ignore-gamelist               Ignore the gamelist files (useful for troubleshooting)
--show-hidden-files             Show hidden files and folders
--show-hidden-games             Show hidden games
--draw-framerate                Display the framerate
--no-exit                       Don't show the exit option in the menu
--no-splash                     Don't show the splash screen
--debug                         Print debug information
--vsync [1/on or 0/off]         Turn vsync on or off (default is on)
--max-vram [size]               Max VRAM to use in Mb before swapping
                                Set to at least 20 to avoid unpredictable behavior
--force-full                    Force the UI mode to Full
--force-kid                     Force the UI mode to Kid
--force-kiosk                   Force the UI mode to Kiosk
--force-disable-filters         Force the UI to ignore applied filters in gamelist
--home [path]                   Directory to use as home path
--version, -v                   Displays version information
--help, -h                      Summon a sentient, angry tuba
```

As long as ES hasn't frozen, you can always press F4 to close the application.

As you can see above, you can override the home directory path using the `--home` flag. So by running for instance the command `emulationstation --home ~/games/emulation`, ES will use `~/games/emulation/.emulationstation` as its base directory.


es_systems.cfg
==============

The es_systems.cfg file contains the system configuration data for EmulationStation, written in XML format. \
This tells EmulationStation what systems you have, what platform they correspond to (for scraping), and where the games are located.

ES will only check in your home directory for an es_systems.cfg file, for example `~/.emulationstation/es_systems.cfg`.

The order EmulationStation displays systems reflects the order you define them in. In the case of the default es_systems.cfg file, the systems are listed in alphabetical order.

**Note:** A system *must* have at least one game present in its `path` directory, or ES will ignore it! If no valid systems are found, ES will report an error and quit.

Here's an overview of the file layout:

```xml
<?xml version="1.0"?>
<!-- This is the EmulationStation-DE game systems configuration file. -->
<systemList>
    <!-- Here's an example system to get you started. -->
    <system>
        <!-- A short name, used internally. -->
        <name>snes</name>

        <!-- A "pretty" name, displayed in the menus and such. This one is optional. -->
        <fullname>Super Nintendo Entertainment System</fullname>

        <!-- The path to start searching for ROMs in. '~' will be expanded to $HOME or %HOMEPATH%, depending on platform.
        The optional %ROMPATH% variable will expand to the path defined for the setting ROMDirectory in es_settings.cfg.
        All subdirectories (and non-recursive links) will be included. -->
        <path>%ROMPATH%/snes</path>

        <!-- A list of extensions to search for, delimited by any of the whitespace characters (", \r\n\t").
        You MUST include the period at the start of the extension! It's also case sensitive. -->
        <extension>.smc .SMC .sfc .SFC .swc .SWC .fig .FIG .bs .BS .bin .BIN .mgd .MGD .7z .7Z .zip .ZIP</extension>

        <!-- The command executed when a game is launched. A few special variables are replaced if found in a command, like %ROM% (see below).
        This example would run RetroArch with the the snes9x_libretro core.
        If there are spaces in the path or file name, you must enclose them in quotation marks, for example:
        retroarch -L "~/my configs/retroarch/cores/snes9x_libretro.so" %ROM% -->
        <command>retroarch -L ~/.config/retroarch/cores/snes9x_libretro.so %ROM%</command>

        <!-- This is an example for Windows. The .exe extension is optional and both forward slashes and backslashes are allowed as
        directory separators. As there is no standardized installation directory structure for this operating system, the %EMUPATH%
        variable is used here to find the cores relative to the RetroArch binary. This binary must be in the PATH environmental variable
        or otherwise the complete path to the retroarch.exe file needs to be defined. Batch scripts (.bat) are also supported. -->
        <command>retroarch.exe -L %EMUPATH%\cores\snes9x_libretro.dll %ROM%</command>

        <!-- Another example for Windows. As can be seen here, the absolut path to the emulator has been defined, and there are spaces
        in the directory name, so it needs to be surrounded by quotation marks. As well the quotation marks are needed around the core
        configuration as the %EMUPATH% will expand to the path of the emulator binary, which will of course also include the spaces. -->
        <command>"C:\My Games\RetroArch\retroarch.exe" -L "%EMUPATH%\cores\snes9x_libretro.dll" %ROM%</command>

        <!-- An example for use in a portable emulator installation, for instance on a USB memory stick. The %ESPATH% variable is
        expanded to the directory of the ES executable. -->
        <command>"%ESPATH%\..\RetroArch\retroarch.exe" -L "%ESPATH%\..\RetroArch\cores\snes9x_libretro.dll" %ROM%</command>

        <!-- The platform(s) to use when scraping. You can see the full list of supported platforms in src/PlatformIds.cpp.
        It's case sensitive, but everything is lowercase. This tag is optional.
        You can use multiple platforms too, delimited with any of the whitespace characters (", \r\n\t"), e.g.: "megadrive, genesis" -->
        <platform>snes</platform>

        <!-- The theme to load from the current theme set. See THEMES.md for more information. -->
        <theme>snes</theme>
    </system>
</systemList>
```

The following variables are expanded by ES for the `command` tag:

`%ROM%` - Replaced with absolute path to the selected ROM, with most Bash special characters escaped with a backslash.

`%BASENAME%` - Replaced with the "base" name of the path to the selected ROM. For example, a path of `/foo/bar.rom`, this tag would be `bar`. This tag is useful for setting up AdvanceMAME.

`%ROM_RAW%`	- Replaced with the unescaped, absolute path to the selected ROM.  If your emulator is picky about paths, you might want to use this instead of %ROM%, but enclosed in quotes.

`%EMUPATH%` - Replaced with the path to the emulator binary. This is expanded either using the PATH environmental variable of the operating system, or if an absolute emulator path is defined, this will be used instead. This variable is mostly useful to define the emulator core path for Windows, as this operating system does not have a standardized program installation directory structure.

`%ESPATH%` - Replaced with the path to the EmulationStation binary. Mostly useful for portable emulator installations, for example on a USB memory stick.

For the `path` tag, the following variable is expanded by ES:

`%ROMPATH%` - Replaced with the path defined for the setting ROMDirectory in `es_settings.cfg`.


gamelist.xml
============

The gamelist.xml file for a system defines metadata for games, such as a name, description, release date, and rating.

As of the fork to EmulationStation Desktop Edition, game media information no longer needs to be defined in the gamelist.xml files. Instead the application will look for any media matching the ROM filename. The media path where to look for game art is configurable either manually in `es_settings.cfg` or via the GUI. If configured manually in es_settings.cfg, it looks something like this:

`<string name="MediaDirectory" value="~/games/images/emulationstation" />`

The default game media directory is `~/.emulationstation/downloaded_media`.

You can use ES's [scraping](http://en.wikipedia.org/wiki/Web_scraping) tools to populate the gamelist.xml files. There are two ways to run the scraper:

* **If you want to scrape multiple games:** press the Start button to open the menu and choose the "SCRAPER" option.  Adjust your settings and press "START".
* **If you just want to scrape one game:** find the game on the game list in ES and press the Select button.  Choose "EDIT THIS GAME'S METADATA" and then press the "SCRAPE" button at the bottom of the metadata editor.

You can also edit metadata within ES by using the metadata editor - just find the game you wish to edit on the gamelist, press Select, and choose "EDIT THIS GAME'S METADATA."

The switch `--ignore-gamelist` can be used to ignore the gamelists upon start of the application.

**File location and structure:**

ES checks for the `gamelist.xml` files in the user's home directory:

`~/.emulationstation/gamelists/[SYSTEM_NAME]/gamelist.xml`

The home directory can be overridden using the `--home` option from the command line, see above in this document for details regarding that.

An example gamelist.xml:

```xml
<gameList>
	<game>
		<path>./mm2.nes</path>
		<name>Mega Man 2</name>
		<desc>Mega Man 2 is a classic NES game which follows Mega Man as he murders eight robot masters in cold blood.</desc>
	</game>
</gameList>
```

Everything is enclosed in a `<gameList>` tag.  The information for each game or folder is enclosed in a corresponding tag (`<game>` or `<folder>`).  Each piece of metadata is encoded as a string.

**gamelist.xml reference:**

There are a few types of metadata:

* `string` - just text.
* `float` - a floating-point decimal value (written as a string).
* `integer` - an integer value (written as a string).
* `datetime` - a date and, potentially, a time.  These are encoded as an ISO string, in the following format: "%Y%m%dT%H%M%S%F%q".  For example, the release date for Chrono Trigger is encoded as "19950311T000000" (no time specified).

Some metadata is also marked as "statistic" - these are kept track of by ES and do not show up in the metadata editor. They are shown in certain views (for example, the detailed view and the video view both show `lastplayed`, although the label can be disabled by the theme).

#### `<game>`

* `name` - string, the displayed name for the game.
* `desc` - string, a description of the game.  Longer descriptions will automatically scroll, so don't worry about size.
* `rating` - float, the rating for the game, expressed as a floating point number between 0 and 1. ES will round fractional values to half-stars.
* `releasedate` - datetime, the date the game was released.  Displayed as date only, time is ignored.
* `developer` - string, the developer for the game.
* `publisher` - string, the publisher for the game.
* `genre` - string, the (primary) genre for the game.
* `players` - integer, the number of players the game supports.
* `favorite` - bool, indicates whether the game is a favorite.
* `completed`- bool, indicates whether the game has been completed.
* `broken` - bool, indicates a game that doesn't work (useful for MAME).
* `kidgame` - bool, indicates whether the game is suitable for children, used by the `kid' UI mode.
* `playcount` - integer, the number of times this game has been played.
* `lastplayed` - statistic, datetime, the last date and time this game was played.
* `sortname` - string, used in sorting the gamelist in a system, instead of `name`.
* `launchcommand` - optional tag that is used to override the emulator and core settings on a per-game basis.

#### `<folder>`
* `name` - string, the displayed name for the folder.
* `desc` - string, the description for the folder.
* `developer` - string, developer(s).
* `publisher` - string, publisher(s).
* `genre` - string, genre(s).
* `players` - integer, the number of players the game supports.


**Additional gamelist.xml information:**

* If a value matches the default for a particular piece of metadata, ES will not write it to the gamelist.xml (for example, if `genre` isn't specified, ES won't write an empty genre tag)

* A `game` can actually point to a folder/directory if the folder has a matching extension

* `folder` metadata will only be used if a game is found inside of that folder

* ES will keep entries for games and folders that it can't find the game/ROM files for

* The switch `--gamelist-only` can be used to skip automatic searching, and only display games defined in the system's gamelist.xml

* The switch `--ignore-gamelist` can be used to ignore the gamelist upon start of the application