wxWidgets - wxWidgets: Cross-Platform GUI Library
RetroArch - RetroArch is a frontend for emulators, game engines and media players.
Electron - Build cross platform desktop apps with web technologies
Playnite - Source code generated using layoutit.com
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Batocera.linux - Batocera.linux is an open-source and completely free retro-gaming distribution that can be copied to a USB stick or an SD card with the aim of turning any computer/nano computer into a gaming console during a game or permanently.