**Note:** This is a quite technical document intended for those that are interested in compiling ES-DE from source code, or would like to customize the configuration. If you just want to start using the software, check out [USERGUIDE-DEV.md](USERGUIDE-DEV.md) instead.
Also note that this document is only relevant for the current ES-DE development version, if you would like to see the documentation for the latest stable release, refer to [INSTALL.md](INSTALL.md) instead.
Table of contents:
[[_TOC_]]
## Development Environment
ES-DE is developed and compiled using Clang/LLVM and GCC on Unix, Clang/LLVM on macOS and MSVC and GCC (MinGW) on Windows.
CMake is the build system for all the supported operating systems, used in conjunction with `make` on Unix and macOS and `nmake` and `make` on Windows. Xcode on macOS or Visual Studio on Windows are not required for building ES-DE and they have not been used during the development. The only exception is notarization of codesigned macOS packages which require the `altool` and `stapler` binaries that come bundled with Xcode.
Go to [https://rpmfusion.org/Configuration](https://rpmfusion.org/Configuration) and download the .rpm package for the free repository. Then install it, followed by VLC:
Note: The Raspberry Pi 4 is the minimum recommended model to use with ES-DE. As this type of device is quite weak and because the FFmpeg video player does not support hardware decoding on this platform, it's strongly adviced to build with the VLC player, which is hardware accelerated.
NetBSD ships with GCC by default, and although you should be able to use Clang/LLVM, it's probably easier to just stick to the default compiler environment. The reason why the clang package needs to be installed is to get clang-format onto the system.
In the same manner as for FreeBSD, Clang/LLVM and cURL should already be installed by default.
RapidJSON is not part of the OpenBSD ports/package collection as of v6.8, so you need to compile it yourself. At the time of writing, the latest release v1.1.0 does not compile on OpenBSD, so you need to use the master branch:
By default the master branch will be used, which is where development takes place. To instead build a stable release, switch to the `stable-x.x` branch for the version, for example:
Keep in mind that a debug version will be much slower due to all compiler optimizations being disabled.
To create a profiling build (optimized with debug symbols), run this:
```
cmake -DCMAKE_BUILD_TYPE=Profiling .
make
```
As for more advanced debugging, Valgrind is a very powerful and useful tool which can analyze many aspects of the application. Be aware that some of the Valgrind tools should be run with an optimized build, and some with optimizations turned off. Refer to the Valgrind documentation for more information.
The most common tool is Memcheck to check for memory leaks, which you run like this:
The output file can be loaded into an application such as Massif-Visualizer for analysis.
Another useful tool is `scan-build`, assuming you use Clang/LLVM. This is a static analyzer that runs during compilation to provide a very helpful HTML report of potential bugs (well it should be actual bugs but some false positives could be included). You need to run it for both the cmake and make steps, here's an example:
You open the report with the `scan-view` command which lets you read it using your web browser. Note that the compilation time is much longer when using the static analyzer compared to a normal build. As well this tool generates a lot of extra files and folders in the build tree, so it may make sense to run it in a separate copy of the source folder to avoid having to clean up all this extra data when the analysis has been completed.
An even more advanced static analyzer is `clang-tidy`, to use it first make sure it's installed on your system and then run the following:
```
cmake -DCLANG_TIDY=on .
```
Even though many irrelevant checks are filtered out via the configuration, this will still likely produce a quite huge report (at least until most of the recommendations have been implemented). In the same manner as for scan-view, the compilation time is much longer when using this static analyzer compared to a normal build.
You will most likely need to install additional packages to get this to build. On Debian-based systems these are _libcec-dev_ and _libp8-platform-dev_. Note that the CEC support is currently untested.
The GLES renderer is quite limited as there is no shader support for it, so ES-DE will definitely not look as pretty as when using the default OpenGL renderer. When building on a Raspberry Pi, the GLES renderer will be automatically selected.
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 ES-DE will install under /usr on Linux, /usr/pkg on NetBSD and /usr/local on FreeBSD and OpenBSD although this can be changed by setting the `CMAKE_INSTALL_PREFIX` variable.
The following example will build the application for installtion under /opt:
It's important to understand that this is not only the directory used by the install script, the CMAKE_INSTALL_PREFIX variable also modifies code inside ES-DE 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.
On Linux, if you're not building a package and instead intend to install using `make install` it's recommended to set the installation prefix to /usr/local instead of /usr.
**Compilers**
Both Clang/LLVM and GCC work fine for building ES-DE.
I did some small benchmarks comparing Clang 10.0 to GCC 9.3.0 with the ES-DE v1.1 codebase on an Intel Xeon W-2245 @ 3.90GHz running Kubuntu 20.04.2 LTS and it's pretty interesting.
* 4% faster application startup time for a debug 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 VSCode 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 25% slower. The same goes for the binary size, instead of 31% smaller it's now 5% larger. The compilation time is still less than GCC but only by 10% instead of 25%.
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 has been used, this is the directory structure for the installation:
```
/usr/bin/emulationstation
/usr/share/man/man6/emulationstation.6.gz
/usr/share/applications/emulationstation.desktop
/usr/share/emulationstation/LICENSE
/usr/share/emulationstation/licenses/*
/usr/share/emulationstation/resources/*
/usr/share/emulationstation/themes/*
/usr/share/pixmaps/emulationstation.svg
```
However, when installing manually instead of building a package, it's recommended to change the install prefix to /usr/local instead of /usr.
Be aware that if using the GNOME desktop environment, /usr/share/pixmaps/emulationstation.svg must exist in order for the ES-DE icon to be shown in the Dash and task switcher.
As indicated above, the home directory will always take precedence and any resources or themes located there will override the ones in the installation path, or in the path of the ES-DE executable.
EmulationStation for macOS is built using Clang/LLVM which is the default compiler for this operating system. It's pretty straightforward to build software on this OS. The main problem is that there is no native package manager, but as there are several third party package managers available, this can be partly compensated for. The use of one of them, [Homebrew](https://brew.sh), is detailed below.
As for code editing, I use [VSCode](https://code.visualstudio.com). I suppose Xcode could be used instead but I have no experience with this tool and no interest in it as I want to use the same tools for all the operating systems that I develop on.
**Setting up the build tools:**
Install the Command Line Tools which include Clang/LLVM, Git, make etc. Simply open a terminal and enter the command `clang`. This will open a dialog that will let you download and install the tools.
Following this, install the Homebrew package manager which will greatly simplify the rest of the installation. Install it by runing the following in a terminal window:
The FFmpeg build distributed via Homebrew has a lot of dependencies we don't need, and which would make it very difficult to package the application. Instead we will build this software with only some limited options:
It makes me wonder who designed this functionality and what was their thinking, I've never seen anything like this on any of the other systems I've been developing on.
If required, define SDKROOT. This is only needed if during compilation you get error messages regarding missing include files. Running the following will properly setup the development environment paths:
By default the master branch will be used, which is where development takes place. To instead build a stable release, switch to the `stable-x.x` branch for the version, for example:
After building ES-DE and trying to execute the application, there could be issues with finding the dynamic link libraries for VLC (assuming VLC was enabled for the build) as these are not installed into a standard location but rather into the /Applications folder. As such, you may need to set the DYLD_LIBRARY_PATH environmental variable to find the VLC libraries. Note that this is not intended or required for the release build that will be shipped in a DMG installer or if you manually install ES-DE using _make install_. It's only needed to be able to run the binary from the build directory. You should add this to your shell profile file to avoid having to set it each time you open a new terminal window:
Running ES-DE from the build directory may be a bit flaky as there is no Info.plist file available which is required for setting the proper window mode and such. It's therefore recommended to run the application from the installation directory for any more in-depth testing. But normal debugging can of course be done from the build directory.
Be aware that the approach taken for macOS has the limitation that you can't build for previous operating system versions. You can certainly set CMAKE_OSX_DEPLOYMENT_TARGET to whatever version you like, but the problem is that the Homebrew libraries will most likely not work on earlier macOS versions. In theory this can be worked around by building all these libraries yourself with a lower deployment target, but it's hardly worth the effort. It's better to build on the lowest OS version that should be supported and rely on forward compatibility.
Due to the Apple notarization requirement implemented as of macOS 10.14.5 a build with simple code signing is needed for versions up to 10.13 and another build with both code signing and notarization is required for version 10.14 and higher.
macOS code signing is beyond the scope of this document, but the option MACOS_CODESIGN_IDENTITY is used to specify the code signing certificate identity, for example:
Assuming the code signing ceritificate is properly setup in Keychain Access, the process will be automatic and the resulting DMG package can be notarized as-is.
Normally ES-DE is meant to be built for macOS 10.14 and higher, but a legacy build for earlier operating system versions can be enabled. This has been tested with a minimum version of 10.11. It's unclear if it works with even older macOS versions.
To enable a legacy build, change the CMAKE_OSX_DEPLOYMENT_TARGET variable in CMakeLists.txt from 10.14 to whatever version you would like to build for. This will disable Hardened Runtime if signing is enabled and it will add 'legacy' to the DMG installer file name when running CPack.
You also need to modify es-app/assets/EmulationStation-DE_Info.plist and set the key SMinimumSystemVersion to the version you're building for.
As macOS does not have any package manager which would have handled the library dependencies, we need to bundle the required shared libraries with the application. Copy the following .dylib files from their respective installation directories to the emulationstation-de build directory:
There are some secondary internal dependencies between some of these library files, and these are baked into the files as absolute paths. As such we need to rewrite these to rpaths (relative paths) which is done using the install_name_tool command.
It's unclear why the first line shows a reference to itself, and this line apparently can't be modified using the install_name_tool command. It doesn't matter though and the application will work fine even if this path does not exist on the system.
You of course only need to change the absolute paths to rpaths once, well at least until you replace the libraries in case of moving to a newer version or so.
In addition to these libraries, if building with the optional VLC video player, you need to create a `plugins` directory and copy over the following libraries, which are normally located in `/Applications/VLC.app/Contents/MacOS/plugins/`:
As indicated above, the home directory will always take precedence and any resources or themes located there will override the ones in the path of the ES-DE executable.
Generating .dmg installers on older version of macOS seems to make them forward compatible to a pretty good extent, for instance building on El Capitan seems to generate an application that is usable on Catalina and Big Sur. The other way around is not true due to the use of dependencies from the Homebrew repository.
Even after considerable effort I've been unable to make CMake natively set correct rpaths for the EmulationStation binary on macOS. Therefore a hack/workaround is in place that uses install_name_tool to change absolute paths to rpaths for most of the bundled libraries.
This is certainly not perfect as the versions of the libraries are hardcoded inside es-app/CMakeLists.txt. Therefore always check that all the rpaths are set correctly if you intend to create a .dmg image that will be used on other computers than your own.
Simply run `otool -L EmulationStation` and verify that the result looks something like this:
If any of the lines that should start with @rpath instead has an absolute path, then you have a problem and need to modify the install_name_tools parameters in es-app/CMakeLists.txt.
This is what an incorrect line would look like:
`/usr/local/opt/sdl2/lib/libSDL2-2.0.0.dylib (compatibility version 13.0.0, current version 13.0.0)`
## Building on Windows
Both MSVC and MinGW (GCC) work fine for building ES-DE on Windows.
Although I would prefer to exclude support for MSVC, this compiler simply works much better when developing as it's much faster than MinGW when linking debug builds and when actually debugging. But for release builds MinGW is very fast and ES-DE starts around 18% faster when built with MinGW meaning this compiler probably generates more efficient code overall. As well MSVC requires a lot more junk DLL files to be distributed with the application so it's not a good candidate for the final release build.
It seems as if Microsoft has dropped support for installing the Build Tools without the Visual Studio IDE, at least I've been unable to find a way to exclude it. But I just pretend it's not installed and use VSCode instead which works perfectly fine.
During installation, choose the Desktop development with C++ workload with the following options (version details excluded):
If you intend to use both MinGW and MSVC on the same machine, it's probably better to exclude CMake and install it manually as described in the MinGW setup instructions below.
The way the MSVC environment works is that a specific developer shell is provided where the build environment is properly configured. You open this from the Start menu via `Visual Studio 2019` -> `Visual Studio tools` -> `VC` -> `x64 Native Tools Command Prompt for VS 2019`.
It's very important to choose the x64-specific shell and not the x86 variant, as ES-DE will only compile as a 64-bit application.
Note that most GDB builds for Windows have broken Python support so that pretty printing won't work. The recommended MinGW distribution should work fine though.
Configure Git. I won't get into the details on how this is done, but there are many resources available online to support with this. The `Git Bash` shell shipped with Git for Windows is very useful though as it's somewhat reproducing a Unix environment using MinGW/MSYS2.
It's strongly recommended to set line breaks to Unix-style (line feed only) directly in the editor. But if not done, lines breaks will anyway be converted when running clang-format on the code, as explained [here](INSTALL-DEV.md#using-clang-format-for-automatic-code-formatting).
In the descriptions below it's assumed that all build steps for MinGW/GCC will be done in the Git Bash shell, and all the build steps for MSVC will be done in the MSVC developer console (x64 Native Tools Command Prompt for VS).
If using MinGW, this library needs to be compiled from source as the pre-built libraries don't seem to work with GCC. The GitHub repo seems to be somewhat broken as well, therefore the manual download is required. It's recommended to get the source in zip format and uncompress it to the same directory as the other libraries listed above.
Then simply build the required glew32.dll library:
```
unzip glew-2.1.0.zip
cd glew-2.1.0
make
```
You will probably see a huge amount of compiler warnings, and the glewinfo.exe tool may fail to build, but we don't need it so it's not an issue.
If using MSVC, simply download the binary distribution of GLEW.
The following packages are not readily available for Windows, so clone the repos and build them yourself:
By default the master branch will be used, which is where development takes place. To instead build a stable release, switch to the `stable-x.x` branch for the version, for example:
**Copy the required library files to the ES-DE 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 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.
In addition to these files, you need libcurl-x64.lib and libvlc.lib (if building with the VLC video player), but these are not available for download so you need to generate them yourself from their corresponding DLL files. Do this inside the respective library directory and not within the emulationstation-de folder.
In addition to the files above, you need to copy some libraries from the VLC `plugins` folder. This contains a subdirectory structure but there is no requirement to retain this as libVLC apparently looks recursively for the .dll files.
The reason to not simply copy all plugins is that the combined size of these is around 120 MB (as of VLC version 3.0.11) and the size of the selected files listed above is around 22 MB, which is more reasonable.
Place the files in the `emulationstation-de\plugins\` directory.
There is a bug in libVLC when building using MSVC, so three lines need to be commented out from `libvlc_media.h`. The compiler error messages will provide you with the line numbers, but they involve the callback `libvlc_media_read_cb`.
For some annoying reason MSVC is the only compiler that creates a debug build by default and where you need to explicitly set the build type to Release.
Unfortunately nmake does not support parallel compiles so it's very slow. There are third party solutions to get multi-core building working with MSVC, but I've not investigated this in depth.
Be aware that MSVC links against different VC++ libraries for debug and release builds (e.g. MSVCP140.dll or MSVCP140d.dll), so any NSIS package made from a debug build will not work on computers without the MSVC development environment installed.
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.
You run a parallel build using multiple CPU cores with the `-j` flag, for example, `make -j6`.
Note that compilation time is much longer than on Unix or macOS, and linking time is unendurable for a debug build (around 10 times longer on my computer compared to Linux). The debug binary is also much larger than on Unix.
**Running with OpenGL software rendering:**
If you are running Windows in a virtualized environment such as QEMU-KVM that does not support HW accelerated OpenGL, you can install the Mesa3D for Windows library, which can be downloaded at [https://fdossena.com/?p=mesa/index.frag](https://fdossena.com/?p=mesa/index.frag).
You simply extract the opengl32.dll file into the ES-DE directory and this will enable the llvmpipe renderer. The performance will be terrible of course, but everything should work and it should be good enough for test building on Windows without having to reboot your computer to a native Windows installation. (Note that you may need to copy opengl32.dll to your RetroArch installation directory as well to get the emulators to work somehow correctly.)
As indicated above, the home directory will always take precedence and any resources or themes located there will override the ones in the path of the ES-DE executable.
There is a style configuration file named .clang-format located directly at the root of the repository which contains the formatting rules. How to install clang-format is detailed per operating system earlier in this document.
But the recommended approach is to run clang-format from within the editor. If using VSCode, there is an extension available named Clang-Format. After installing this, simply open a source file, right click and choose `Format Document` or use the applicable keyboard shortcut. The first time you do this, you will have to make a choice to perform the formatting using clang-format. The rest should be completely automatic.
In some instances you may want to avoid getting code formatted, and you can accomplish this by simply enclosing the lines with the two comments "clang-format off" and "clang-format on", such as this:
Adding a comment on its own line will also prevent some formatting such as turning short functions and lambda expressions into single lines. For this function such a comment has been added:
Of course you would like to get the code formatted according to the clang-format rules in most instances, these workaround are only meant for rare exceptions. Some compromises are necessary when auto-formatting code, at least with clang-format in its current state.
There are some files shipped with ES-DE that need to be pulled from external resources, the first one being the CA certificate bundle to get TLS/SSL support working on Windows.
The CA certificates shipped with ES-DE come directly from the curl project but they're originally supplied by the Mozilla foundation. See [https://wiki.mozilla.org/CA](https://wiki.mozilla.org/CA) for more information about this certificate bundle.
The latest version can be downloaded from [https://curl.se/docs/caextract.html](https://curl.se/docs/caextract.html)
After downloading the file, rename it from `cacert.pem` to `curl-ca-bundle.crt` and move it to the certificates directory i.e.:
ES-DE automatically identifies and excludes MAME BIOS and device files, as well as translating the short MAME ROM names to their full game names. This is done using information from the MAME driver file shipped with the official MAME distribution. The file needs to be converted to an internal format used by ES-DE as the original file is huge and most of the information is not required.
To get hold of the driver file, go to [https://www.mamedev.org/release.php](https://www.mamedev.org/release.php) and select the Windows version, but only download the driver information in XML format and not MAME itself. This file will be named something like `mame0226lx.zip` and unzipping it will give you a file name such as `mame0226.xml`.
You need `xmlstarlet` installed for these scripts to work.
The diff command is used to do a sanity check that the changes look reasonable before deleting the old files. This is an example for the BIOS file when going from driver version 0.221 to 0.226:
```
diff mamebioses.xml mamebioses.xml_OLD
1c1
<<!-- Last updated with information from MAME driver file mame0226.xml -->
---
> <!-- Last updated with information from MAME driver file mame0221.xml -->
51d50
<<bios>kpython</bios>
```
You can also use git for this comparison of course, which may actually provide a clearer visualization of the changes:
The reason to not simply replace the BIOS and devices files with the new version is that we want to retain entries from all older MAME versions as otherwise older ROM sets used on older MAME versions would have missing information. This is so as the MAME project sometimes removes older entries when they're reorganizing the ROM sets. By merging the files we retain backward compatibility but still support the latest MAME version. To clarify, this of course does not affect the emulation itself, but rather the filtering of BIOS and device files inside ES-DE. The mamenames.xml file containing the translation of MAME ROM names to the full game names does not suffer from this problem as it's cumulative, which is why it is simply overwritten.
This file will contain all supported settings 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-DE to update all the necessary settings.
This complete configuration step can normally be skipped as you're presented with a dialog to change the ROM directory upon application startup if no game files are found.
By default, ES-DE looks in `~/ROMs` for the ROM files, where they are expected to be grouped into directories corresponding to the game systems, for example:
There is also support to add the variable %ESPATH% to the ROM directory setting, this will expand to the path where the ES-DE executable is started from. You should normally not need this, but the option is there for special cases. For example:
As ES-DE auto-configures the keyboard and controllers, neither the input configuration step or manual adjustments to the es_input.xml file should normally be needed. Actually, unless the button layout has been customized using the input configurator, the es_input.xml file will not even exist.
But if you have customized your button layout and your controller or keyboard stop working, you can delete the `~/.emulationstation/es_input.xml` file to remove the customizations, or you can start ES-DE with the `--force-input-config` command line option to make the input configurator appear.
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-DE will use `~/games/emulation/.emulationstation` as its application home directory. Be aware that this option completely replaces what is considered the home directory, meaning the default ROM directory ~/ROMs would be resolved to ~/games/emulation/ROMs. The same is true for the emulator core locations if es_find_rules.xml is configured to look for them relative to the home directory. So of course RetroArch and other emulators would also need to be configured to use ~/games/emulation as its base directory in this instance.
The es_systems.xml file contains the game systems configuration data for ES-DE, written in XML format. This defines the system name, the full system name, the ROM path, the allowed file extensions, the launch command, the platform (for scraping) and the theme to use.
ES-DE ships with a comprehensive `es_systems.xml` file and most users will probably never need to make any customizations. But there may be special circumstances such as wanting to use different emulators for some game systems or perhaps to add additional systems altogether.
To accomplish this, ES-DE supports customizations via a separate es_systems.xml file that is to be placed in the `custom_systems` folder in the application home directory, i.e. `~/.emulationstation/custom_systems/es_systems.xml`. (The tilde symbol `~` translates to `$HOME` on Unix and macOS, and to `%HOMEPATH%` on Windows unless overridden via the --home command line option.)
This custom file functionality is designed to be complementary to the bundled es_systems.xml file, meaning you should only add entries to the custom configuration file for game systems that you actually want to add or override. So to for example customize a single system, this file should only contain a single `<system>` tag. The structure of the custom file is identical to the bundled file with the exception of an additional optional tag named `<loadExclusive/>`. If this is placed in the custom es_systems.xml file, ES-DE will not load the bundled file. This is normally not recommended and should only be used for special situations. At the end of this section you can find an example of a custom es_systems.xml file.
The bundled es_systems.xml file is located in the resources directory that is part of the application installation. For example this could be `/usr/share/emulationstation/resources/systems/unix/es_systems.xml` on Unix, `/Applications/EmulationStation Desktop Edition.app/Contents/Resources/resources/systems/macos/es_systems.xml` on macOS or `C:\Program Files\EmulationStation-DE\resources\systems\windows\es_systems.xml` on Windows. The actual location may differ from these examples of course, depending on where ES-DE has been installed.
It doesn't matter in which order you define the systems as they will be sorted by the full system name inside the application, but it's still probably a good idea to add them in alphabetical order to make the file easier to maintain.
Keep in mind that you have to set up your emulators separately from ES-DE as the es_systems.xml file assumes that your emulator environment is properly configured.
Below is an overview of the file layout with various examples. For the command tag, the newer es_find_rules.xml logic described later in this document removes the need for most of the legacy options, but they are still supported for special configurations and for backward compatibility with old configuration files.
`%ROMRAW%` - 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.
`%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.
`%EMUPATH%` - Replaced with the path to the emulator binary. This is expanded using either the PATH environmental variable of the operating system, or using an absolute emulator path if this has been defined.
`%ESPATH%` - Replaced with the path to the ES-DE binary. Mostly useful for portable emulator installations, for example on a USB memory stick.
`%EMULATOR_` - This utilizes the emulator find rules as defined in `es_find_rules.xml`. This is the recommended way to configure the launch command. The find rules are explained in more detail below.
`%CORE_` - This utilizes the core find rules as defined in `es_find_rules.xml`. This is the recommended way to configure the launch command.
`%HIDEWINDOW%` - This variable is only available on Windows and is used primarily for hiding console windows when launching scripts (used for example by Steam games and source ports). If not defining this, the console window will be visible when launching the game. It needs to be placed first in the command tag.
As well, here's an example for Unix of a custom es_systems.xml file placed in ~/.emulationstation/custom_systems/ that overrides a single game system from the bundled configuration file:
<!-- This is a custom ES-DE game systems configuration file for Unix -->
<systemList>
<system>
<name>nes</name>
<fullname>Nintendo Entertainment System</fullname>
<path>%ROMPATH%/nes</path>
<extension>.nes .NES .zip .ZIP</extension>
<command>/usr/games/fceux %ROM%</command>
<platform>nes</platform>
<theme>nes</theme>
</system>
</systemList>
```
If adding the `<loadExclusive/>` tag to the file, the bundled es_systems.xml file will not be processed. For this example it wouldn't be a very good idea as NES would then be the only platform that could be used in ES-DE.
```xml
<?xml version="1.0"?>
<!-- This is a custom ES-DE game systems configuration file for Unix -->
<loadExclusive/>
<systemList>
<system>
<name>nes</name>
<fullname>Nintendo Entertainment System</fullname>
The file is located in the resources directory in the same location as the es_systems.xml file, but a customized copy can be placed in ~/.emulationstation/custom_systems, which will override the bundled file.
It's pretty straightforward, there are currently three rules supported for finding emulators, `winregistrypath`, `systempath` and `staticpath` and there is one rule supported for finding the emulator cores, `corepath`.
Of these, `winregistrypath` is only available on Windows, and attempting to use the rule on any other operating system will generate a warning in the log file when processing the es_find_fules.xml file.
Here %EMULATOR_ and %CORE_ are followed by the string RETROARCH which corresponds to the name attribute in es_find_rules.xml. The name is case sensitive but it's recommended to use uppercase names to make the variables feel consistent (%EMULATOR_retroarch% doesn't look so pretty).
The `winregistrypath` rule searches the Windows Registry "App Paths" keys for the emulators defined in the `<entry>` tags. If for example this tag is set to `retroarch.exe`, the key `SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\retroarch.exe` will be searched for. HKEY_CURRENT_USER is tried first, and if no key is found there, HKEY_LOCAL_MACHINE is tried as well. In addition to this, ES-DE will check that the binary defined in the key actually exists, and if not, it will proceed with the next rule. Be aware that the App Paths keys are added by the emulators during their installation, and although RetroArch does add this key, not all emulators do.
The other rules are probably self-explanatory with `systempath` searching the PATH environment variable for the binary names defined by the `<entry>` tags and `staticpath` defines absolute paths to the emulators. For staticpath, the actual emulator binary must be included in the entry tag.
The winregistrypath rules are always processed first, followed by systempath and then staticpath. This is done regardless of which order they are defined in the es_find_rules.xml file.
As for `corepath` this rule is simply a path to search for the emulator core.
Each rule supports multiple entry tags which are tried in the order that they are defined in the file.
The %ESPATH% and %ROMPATH% variables can be used inside the staticpath rules and the %ESPATH% and %EMUPATH% variables can be used inside the corepath rules.
The tilde symbol `~` is supported for the staticpath and corepath rules and will expand to the user home directory. Be aware that if ES-DE has been started with the --home command line option, the home directory is considered to be whatever path was passed as an argument to that option. The same is true if using a portable.txt file.
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 media is configurable either manually in `es_settings.xml` or via the GUI. If configured manually in es_settings.xml, it looks something like this:
There is also support to add the variable %ESPATH% to the media directory setting, this will expand to the path where the ES-DE executable is started from. You should normally not need this, but the option is there for special cases. For example:
You can use ES-DE's scrapers to populate the gamelist.xml files, or manually update individual entries using the metadata editor. All of this is explained in the [User guide](USERGUIDE-DEV.md).
An example gamelist.xml entry for the Commodore 64 game Popeye:
```xml
<?xml version="1.0"?>
<gameList>
<game>
<path>./cartridge/Popeye/Popeye.crt</path>
<name>Popeye</name>
<desc>Popeye is a conversion of the arcade action/platform game.</desc>
<rating>0.7</rating>
<releasedate>19860101T000000</releasedate>
<developer>Parker Brothers</developer>
<publisher>Nintendo</publisher>
<genre>Action</genre>
<players>1-2</players>
<favorite>true</favorite>
</game>
</gameList>
```
Everything is enclosed in a `<gameList>` tag, and the information for each game or folder is enclosed in a corresponding `<game>` or `<folder>` tag. Each piece of metadata is encoded as a string.
**gamelist.xml reference:**
There are a few different data types for the metadata which the string values in the gamelist.xml files are converted to during file loading:
*`string` - just text
*`float` - a floating-point decimal value (written as a string)
*`integer` - an integer value (written as a string)
Some metadata is also marked as "statistic", these are kept track of by ES-DE 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).
There are two basic categories of metadata, `game` and `folders` and the metdata tags for these are described in detail below.
**\<game\>**
*`path` - string, the path to the game file, either relative to the %ROMPATH% variable or as an absolute path on the filesystem
*`name` - string, the displayed name for the game
*`sortname` - string, used in sorting the gamelist in a system, instead of `name`
*`desc` - string, a description of the game, longer descriptions will automatically scroll, so don't worry about the size
*`rating` - float, the rating for the game, expressed as a floating point number between 0 and 1. Fractional values will be rounded to 0.1 increments (half-stars) during processing
*`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 genre(s) 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
*`kidgame` - bool, indicates whether the game is suitable for children, as used by the `Kid' UI mode
*`hidden` - bool, indicates whether the game is hidden
*`broken` - bool, indicates a game that doesn't work (useful for MAME)
*`nogamecount` - bool, indicates whether the game should be excluded from the game counter and the automatic and custom collections
*`nomultiscrape` - bool, indicates whether the game should be excluded from the multi-scraper
*`hidemetadata` - bool, indicates whether to hide most of the metadata fields when displaying the game in the gamelist view
*`playcount` - integer, the number of times this game has been played
*`lastplayed` - statistic, datetime, the last date and time this game was played
For folders, most of the fields are identical although some are removed. In the list below, the fields with identical function compared to the game files described above have been left without a description.
**\<folder\>**
*`path`
*`name`
*`desc`
*`rating`
*`releasedate`
*`developer`
*`publisher`
*`genre`
*`players`
*`favorite`
*`completed`
*`hidden`
*`broken`
*`nomultiscrape`
*`hidemetadata`
*`lastplayed` - statistic, for folders this is inherited by the latest game file launched inside the folder.
**Additional gamelist.xml information:**
* If a value matches the default for a particular piece of metadata, ES-DE will not write it to the gamelist.xml file (for example, if `genre` isn't specified, an empty genre tag will not be written)
* A `game` can actually point to a folder/directory if the folder has a matching extension, although this is exceedingly rare
* The `folder` metadata will only be used if a game file is found inside that folder, as empty folders will be skipped during startup even if they have metadata values defined for themselves
* ES-DE will keep entries for games and folders that it can't find the game/ROM files for, i.e. it will not clean up the gamelist.xml files automatically when game files are missing
* The switch `--gamelist-only` can be used to skip automatic searching, and only display games defined in the gamelist.xml files
* The switch `--ignore-gamelist` can be used to ignore the gamelist upon start of the application (mostly useful for debugging purposes)
## Debug mode
By passing the --debug command line option, ES-DE will increase the logging to include a lot of additional debug output which is useful both for development and in order to pinpoint issues as a user.
In addition to this extra logging, a few key combinations are enabled when in debug mode. These are useful both for working on ES-DE itself as well as for theme developers.
**Ctrl + g**
This will render a grid on the user interface, most notably in the menus, showing the layout of all the GUI elements. Note that any open screen needs to be closed and reopened again after using the key combination in order for it to have any effect.
**Ctrl + i**
This will draw a semi-transparent red frame behind all image elements.
**Ctrl + t**
This will draw a semi-transparent blue frame around all text elements.
**Ctrl + r**
This will reload either a single gamelist or all gamelists depending on where you're located when entering the key combination (go to the system view to make a complete reload). Very useful for theme development as any changes to the theme files will be activated without requiring an application restart. Note that the menu needs to be closed for this key combination to have any effect.
By default all controller input (keyboard and controller button presses) will be logged when the --debug flag has been passed. To disable the input logging, the setting DebugSkipInputLogging kan be set to false in the es_settings.xml file. There is no menu entry to change this as it's intended for developers and not for end users.
How this works is that when ES-DE finds a file named portable.txt in its executable directory, it will by default locate the .emulationstation directory directly in this folder. It's also possible to modify portable.txt with a path relative to the ES-DE executable directory. For instance if two dots `..` are placed inside the portable.txt file, then the .emulationstation directory will be located in the parent folder, which would be directly under F:\ in this example.
There are numerous locations throughout ES-DE where custom scripts will be executed if the option to do so has been enabled in the settings. You'll find the option on the Main menu under `Other settings`. By default it's deactivated so be sure to enable it to use this feature.
The approach is quite straightforward, ES-DE will look for any files inside a script directory that corresponds to the event that is triggered and will then execute all these files.
**Note:** The following examples are for Unix systems, but it works the same way on macOS (which is also Unix after all), and on Windows (although .bat batch files are then used instead of shell scripts and any spaces in the parameters are not escaped as is the case on Unix).
The events executed when a game starts and ends are called `game-start` and `game-end` respectively. Finding these event names is easily achieved by starting ES-DE with the `--debug` flag. If this is done, all attempts to execute custom event scripts will be logged to es_log.txt, including the event names.
So let's create the folders for these events in the scripts directory. The location is `~/.emulationstation/scripts`
**Game log:**
After creating the directories, we need to create the scripts to log the actual game launch and game ending. The parameters that are passed to the scripts varies depending on the type of event, but for these events the two parameters are the absolute path to the game file, and the game name as shown in the gamelist view.
Let's name the start script `game_start_logging.sh` with the following contents:
```
#!/bin/bash
TIMESTAMP=$(date +%Y-%m-%d' '%H:%M:%S)
echo Starting game "\""${2}"\"" "(\""${1}"\")" at $TIMESTAMP >> ~/.emulationstation/game_playlog.txt
```
And let's name the end script `game_end_logging.sh` with the following contents:
```
#!/bin/bash
TIMESTAMP=$(date +%Y-%m-%d' '%H:%M:%S)
echo "Ending game " "\""${2}"\"" "(\""${1}"\")" at $TIMESTAMP >> ~/.emulationstation/game_playlog.txt
```
After creating the two scripts, you should have something like this on the filesystem:
If we now start ES-DE with the debug flag and launch a game, something like the following should show up in es_log.txt:
```
Aug 05 14:19:24 Debug: Scripting::fireEvent(): game-start "/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip" "The Legend Of Zelda"
Aug 05 14:19:24 Debug: Executing: /home/myusername/.emulationstation/scripts/game-start/game_start_logging.sh "/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip" "The Legend Of Zelda"
.
.
Aug 05 14:27:15 Debug: Scripting::fireEvent(): game-end "/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip" "The Legend Of Zelda"
Aug 05 14:27:15 Debug: Executing: /home/myusername/.emulationstation/scripts/game-end/game_end_logging.sh "/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip" "The Legend Of Zelda"
```
Finally after running some games, ~/.emulationstation/game_playlog.txt should contain something like the following:
```
Starting game "The Legend Of Zelda" ("/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip") at 2020-08-05 14:19:24
Ending game "The Legend Of Zelda" ("/home/myusername/ROMs/nes/Legend\ of\ Zelda,\ The.zip") at 2020-08-05 14:27:15
Starting game "Quake" ("/home/myusername/ROMs/ports/Quakespasm/quakespasm.sh") at 2020-08-05 14:38:46
Ending game "Quake" ("/home/myusername/ROMs/ports/Quakespasm/quakespasm.sh") at 2020-08-05 15:13:58
Starting game "Pirates!" ("/home/myusername/ROMs/c64/Multidisk/Pirates/Pirates!.m3u") at 2020-08-05 15:15:24
Ending game "Pirates!" ("/home/myusername/ROMs/c64/Multidisk/Pirates/Pirates!.m3u") at 2020-08-05 15:17:11
```
**Resolution changes:**
The same directories are used as for the above example with the game log.
First create the game start script, let's name it `set_resolution_1080p.sh` with the following contents:
```
#!/bin/sh
xrandr -s 1920x1080
```
Then create the end script, which we'll name `set_resolution_4K.sh`:
The last two lines are optional, they're used to set the focus back to ES-DE in case you're running attention-seeking applications such as Kodi which may steal focus after resolution changes. You may need to adjust the sleep time to get this to work reliably though, as the timing may differ between different computers and graphics drivers.
After creating the two scripts, you should have something like this on the filesystem:
