**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!
The code has a few dependencies. For building, you'll need CMake and development packages for cURL, FreeImage, FreeType, libVLC, pugixml, SDL2 and RapidJSON.
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:
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.
Both Clang/LLVM and GCC work fine for building ES.
The Microsoft Visual C++ compiler (MSVC) could maybe work as well, there are some old settings in CMakeLists.txt for it. Try it if you want, but I recommend Clang or GCC instead of this legacy compiler.
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.
So overall Clang is interesting and perhaps even a better compiler than GCC, but it needs better integration with VSCodium before it's really usable. For macOS it seems as if Clang is the preferred compiler though, so it's good that ES now fully supports it. (It took quite some effort to get all the compile errors and compile warnings sorted out.)
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++).
The home directory will always take precedence, so any resources located there will override the ones in the installation path. It's not recommended to override any resources since they are by nature static. But using the ability to locate resource files in the home directory is very useful when combined with the command line option `--home` (see below), as a fully portable version of EmulationStation can then be created on a USB memory stick or similar.
The same goes for the `themes` directory. Although ES can start without a theme, it would be pretty pointless as the application would barely be usable.
[FreeType2](http://download.savannah.gnu.org/releases/freetype/freetype-2.4.9.tar.bz2) (you'll need to compile)
[cURL](http://curl.haxx.se/download.html) (you'll need to compile or get the pre-compiled DLL version)
[RapisJSON](https://github.com/tencent/rapidjson) (you need to add `include/rapidsjon` to your include path)
Remember to copy the necessary .DLL files into the same folder as the executable: probably FreeImage.dll, freetype6.dll, SDL2.dll, libcurl.dll, and zlib1.dll. Exact list depends on if you built your libraries in "static" mode or not.
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`.
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.
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:
Keep in mind though that you still need to group the ROMs into directories corresponding to the system names. Well at least if you want to use the default es_systems.cfg file. See below how to customize that file, which gives you full control over the location of the ROMs.
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.**
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.
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.
`%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.
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:
*You can use ES's [scraping](http://en.wikipedia.org/wiki/Web_scraping) tools to avoid creating a gamelist.xml by hand.* 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."
