EmulationStation Desktop Edition (ES-DE) - Contributing

Help needed

Contributions to ES-DE are very much appreciated as there are many things that need to be implemented and improved. Code commits is only one part of it, as work is also needed on the rbsimple-DE theme set as well as thorough application testing.

Additional documentation is needed too, primarily in the form of instruction videos to show how the software is installed and configured on the various supported operating systems. The primary user feedback so far is that although it's quite easy to setup ES-DE itself, the confusion starts with RetroArch and its emulator cores. The scope is clear that ES-DE is only a front-end application, but the instruction videos should cover the entire setup process including the emulators to make them one-stop tutorials for the users.

Regarding testing, it's impossible for me to test every game system as rbsimple-DE has support for well over a 100 different systems. There could be issues with the configuration template files, or within ES-DE itself. So more testing is needed!

In general, a thorough review of es_systems.cfg_unix, es_systems.cfg_macos and es_systems.cfg_windows would be great!

As for rbsimple-DE there are quite some missing graphic files and other customizations for a number of game systems. Check out MISSING.md for more details on what needs to be added or updated. Note that although rbsimple-DE is based on Recalbox Multi, it's only possible to use assets from this theme set created before its change to a more restrictive license, which happened in 2018. As such it's unfortunately necessary to recreate all the system graphics from scratch that have since been released by the Recalbox community.

The ES-DE development is tracked using a Kanban board which is publicly visible at the GitLab project site:

https://gitlab.com/leonstyhre/emulationstation-de/-/boards

High level release plan

This plan is under constant review so expect it to change from time to time. Still it should give some feeling for which direction to move and what to work on first. These are only the larger topics, there are of course many smaller changes and improvements in addition to these.

v1.1

Support for Raspberry Pi 4 with OpenGL ES 2.0 (Ubuntu and Raspberry Pi OS)
Mix image generation based on screenshots, 3D boxes and marquee files (as in Skyscraper)
Improve full-screen support, remove the temporary full screen hacks
Proper game launching screen
Ability to show game media in full screen from the gamelist view
Replace libVLC with FFmpeg
Move to the SDL2 GameController API

v1.2

Badges highlighting things like favorite games, completed games etc. (will require theme support)
On-screen keyboard
Different button graphics and names applied depending on controller type (Xbox, PlayStation and SNES style)
Checksum support for the scraper to verify each file before accepting/saving it
Web proxy support for the scraper
Add GLM library dependency for matrix and vector operations, decommissioning the built-in functions
Shader support for the OpenGL ES renderer
Add to Linux repositories, BSD ports collections etc.

v1.3

Localization/multi-language support.
Internationalization/multi-language support
Complete overhaul of the grid view style
A nice and useful grid view implementation in rbsimple-DE
Better shader support (more adaptive to screen resolution, higher performance, cleaner code)
Improved text and font functions, e.g. faster and cleaner line wrapping
Flatpak and Snap support on Linux

v1.4

Authoring tools to clean up orphaned gamelist entries, media files etc.
Support for pre-defined alternative emulators and cores (configured in es_systems.cfg)
Simple file browsing component
Requests per minute limitation setting for the scraper
Add 'time played' counter per game, similar to how it works in Steam
Preload all built-in resources and never clear them from the cache
Improved multi-threading

v1.5

Bulk metadata editor
Overhaul of the GUI element scaling and placement logic to make ES-DE look more consistent across different resolutions
Scrollbars for menus and gamelists
Animated menu elements like switches, tick boxes, smooth scrolling etc.
Support for additional scraper services (if feasible?)

v2.0

Vulkan renderer for all supported operating systems
Dependency on MoltenVK to get Metal support on macOS
Decommission of the OpenGL 2.1 and OpenGL ES renderers (or keep as legacy mode/legacy build?)
Better and more accurate GPU and memory usage statistics overlay

v2.1

Migration tools for importing game metadata and media from other front-end applications
Auto-import tools for Steam, Lutris etc.

To see which features have been implemented in previous versions, please refer to CHANGELOG.md.

Coding style

The coding style for ES-DE is mostly a combination of the Linux kernel style (although that's C it's close enough to C++ as far as I'm concerned) and Google's C++ guidelines.

Please refer to these documents here:

https://www.kernel.org/doc/html/v4.10/process/coding-style.html
https://google.github.io/styleguide/cppguide.html

Some key points:

Column width (line length) is 100 characters
Indentation is 4 spaces, don't use tabs as they can be interpreted differently
Line break is Unix-style (line feed only, no carriage return)
Do not leave trailing whitespaces at the end of the lines (a good source code editor should have a setting to automatically trim these for you)
When breaking up long lines into multiple lines, consider what could be useful data to grep for so you don't break in the middle of such a string
Comments always in C++ style, i.e. // instead of /* */
Comments should be proper sentences, starting with a capital letter and ending with a dot
Use K&R placements of braces, read the Linux kernel coding style document for clarifications
Always use spaces between keywords and opening brackets, i.e. if (), for (), while () etc.
Indentation of switch/case statements is optional, but it's usually easier to read the code with indentations in place
Use std::string or std::vector<char> instead of char * or char [] unless there is a specific reason requiring the latter
Actually, try to use C++ syntax in general instead of C syntax, another example would be static_cast<int>(someFloatVariable) instead of (int)someFloatVariable
If the arguments (and initializer list) for a function or class exceeds 4 items, arrange them vertically to make the code easier to read
Always declare one variable per line, never combine multiple declarations of the same type
Name local variables with the first word in small letters and the proceeding words starting with capital letters, e.g. myExampleVariable
Name member variables starting with an m such as mMyMemberVariable and name static variables with an s such as sMyStaticVariable
Use the same naming convention for functions as for local variables, e.g. someFunction()
Inline functions makes perfect sense to use, but don't overdo it by using them for functions that won't be called very frequently
Don't put more than one statement on a single line (there are some exceptions though like lambda expressions and possibly switch statements)
Avoid overoptimizations, especially if it sacrifices readability, makes the code hard to expand on or is error prone
For the rest, check the code and have fun! :)

Building and configuring

Please refer to INSTALL.md for details on everything related to building ES-DE.

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