ES-DE/CONTRIBUTING.md

EmulationStation Desktop Edition (ES-DE) - Contributing

Help needed

Contributions are very much appreciated as there are many things that need to be implemented and improved.

In addition to the information below about work on ES-DE itself, the project is currently looking for a developer to create a configuration utility for customizing systems (i.e. to avoid having to manually edit XML configuration files). For various reasons this should be a standalone application, and it needs to be cross-platform with support for Windows, macOS and Linux. Get in touch if you would be interested in working on this!

Apart from the above there are basically three areas where help is needed:

• Programming: If you are experienced with developing cross-platform client applications in C++ then ES-DE could be an interesting project! Although the application does not have a huge codebase, it is still fairly complex as it covers many different areas like OpenGL rendering, audio playback, video playback, controller input, network access, XML and JSON parsing etc. To work on the project you need to be able to test your code on Linux, macOS and Windows, but apart from that it should hopefully be fairly straightforward.

• Emulator configuration and testing: As one of the main goals of ES-DE is easy setup, the application needs to ship with all game systems preconfigured. This means that the es_systems.xml files have to be populated with both default and alternative emulators for all supported operating systems. There could also be a need to add additional platforms that ES-DE does not support today. Please refer to USERGUIDE-DEV.md for the current game systems status. You can also review the es_systems.xml files directly: unix/es_systems.xml, macos/es_systems.xml and windows/es_systems.xml.

• Theme creation. With ES-DE v2.0 a new theme engine will be introduced with improved capabilities compared to the current engine. Existing themes would need to be ported over to the new engine, potentially also from other frontends than RetroPie EmulationStation. Completely new themes would also be nice to showcase the new engine.

Another specific area where help is needed is to research and potentially develop a usable web version of ES-DE. A proof of concept compilation to WebAssembly (using Emscripten) has been done and the application actually runs somehow correctly in a browser. But it needs to be investigated whether games/emulators can actually be launched when running in this environment and there are many improvements to be completed before the WebAssembly build is usable.

Merge requests are only accepted from project members so if you would like to contribute to the project then please get in contact and we can discuss what you would like to work on and such.

You can contact me (Leon) via email, either at info@es-de.org or alternatively using the address I use for my code commits. You can also join our Discord server where I go under the username LeonSe.

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

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

Development takes place in the master branch, and bug fixes/point releases are handled in the stable branch.

Only the latest stable version is maintained.

Release roadmap

The roadmap 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. The plans for previous releases are shown in italics.

v1.0

• New gamelist sorting and media handling logic
• Overhaul of the menu system
• Scraping of additional image types as well as videos
• OpenGL shader support for blurred backgrounds, scanline rendering etc.
• Navigation sound support
• A comprehensive theme set bundled with the application
• Ports for Windows, macOS and BSD Unix
• Preconfigured systems configuration files for all supported operating systems
• A detailed user guide

v1.1

• Mix image generation based on screenshots, 3D boxes and marquee files (as in Skyscraper)
• Ability to display game media in full screen from the gamelist view
• Proper game launching screen
• New FFmpeg-based video player
• Better method to find installed emulators and cores
• Move to the SDL2 GameController API
• Different button graphics and names applied depending on controller type (Xbox, PlayStation or SNES style)

v1.2

• Support for pre-defined alternative emulators and cores (configured in es_systems.xml)
• Badges highlighting things like favorite games, completed games etc. (will require theme support)
• Virtual (on-screen) keyboard
• Support for the Raspberry Pi 4 (Raspberry Pi OS)
• Improve fullscreen support and make game launching more seamless, remove the temporary fullscreen hacks
• Add GLM library dependency for matrix and vector operations, decommission the built-in functions
• AppImage and AUR releases on Linux

v2.0 (in progress)

• New theme engine with generalized views (only System and Gamelist) and theme variants support
• Multiple new gamelist components (wheels, wall/grid etc.)
• Lottie animation (vector graphics) and GIF animation support
• OpenGL ES 3.0 renderer for use on the Raspberry Pi
• Replace the OpenGL fixed function pipeline with a shader-based renderer
• Improve the performance of the GLSL shader post-processing

v2.1

• Animated menu elements like switches, tick boxes, smooth scrolling etc.
• New texture/cache manager with support for SVG images and Lottie animations
• Add scraping of game manuals and maps and create a viewer for these (with PDF, GIF, JPG and PNG support)
• Support for additional scraper services (if feasible?)
• Web proxy support for the scraper
• RetroAchievements.org integration
• Add "time played" counter per game, similar to how it works in Steam

v2.2

• Simple file browsing component
• Scrollbar component for the gamelist view which can be used by the themes
• Background music
• Proper audio mixer
• Checksum support for the scraper for exact searches and for determining when to overwrite files
• Support for portrait orientation, e.g. for Tate Mode arcade cabinets
• Improved text and font functions, e.g. faster and cleaner line wrapping and more exact sizing

v2.3

• Vulkan renderer for all supported operating systems
• Localization/multi-language support
• Dependency on MoltenVK to get Metal support on macOS
• Better and more accurate GPU and memory usage statistics overlay
• Bulk metadata editor
• Improve multi-threading

v2.4

• Reorganize the menus, possibly adding basic/advanced modes
• Migration tools for importing game metadata and media from other frontend applications
• Audit tools to clean up orphaned gamelist entries, media files etc.
• Auto-import tools for Steam, Lutris etc.
• Replacements for the abandoned NanoSVG and FreeImage libraries

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

Coding style

The visual appearance aspect of the coding style is automatically applied using clang-format, so to understand the exact formatting rules, refer to the .clang-format file in the root of the repository.

Due to this approach, all code changes must be auto-formatted before they are committed. You can read in INSTALL.md how clang-format is installed and used.

But as clang-format won't change the actual code content or fix all code style choices, here are some additional key points:

• Always write comments in C++ style, i.e. // instead of /* */
• Comments should be proper sentences, starting with a capital letter and ending with a dot
• As a general rule, use C++ syntax instead of C syntax, for example static_cast<int>(someFloatVariable) instead of (int)someFloatVariable
• Always declare one variable per line, never combine multiple declarations of the same type
• Name member variables starting with an m such as mMyMemberVariable and name static variables starting with an s such as sMyStaticVariable
• Use braced initializations when possible, e.g. float myFloat {1.5f} as this is generally the safest way to do it (except when using the auto keyword)
• Short function definitions can be placed in either the .h or .cpp file depending on the situation
• Try to be coherent with the existing codebase regarding names, structure etc., it should not be obvious what person wrote which parts
• For the rest, check the code and have fun :)

Building and configuring

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