Overlays

RetroArch

Overlays should be possible to add when using RetroArch cores. Broadly speaking overlays serve three purposes:

1. To fill the black areas of the screen while playing games that were developed for a different aspect ratio than the device uses (e.g 4:3 games on a 16:9 screen)
2. To simulate scan lines to improve how games originally developed for CRT monitors are displayed on low-powered devices. For high-powered devices you probably want to use a shader
3. To display buttons on devices with touch-screens

Instructions on how to use overlays can be found here: https://docs.libretro.com/guides/libretro-overlays/. Suggested sample configurations for different systems can be found in https://retrogamecorps.com/2024/09/01/guide-shaders-and-overlays-on-retro-handhelds/#Overlays.

The default selection of overlays in Retroarch is limited, additional overlays can be found on Github, see e.g https://github.com/Duimon/Retroarch-Overlays for 16:9 systems or https://github.com/ourigen/perfect_overlays/ for 4:3 screens.

Stand-Alone Emulators

Overlays are not supported for standalone emulators. That said, if you are interested in developing the support to add them please check out how to start contributing here.