As I understand it, RetoArch’s Overlay system has roots in providing a touch interface rather than reproducing integral game artwork. Even though folks successfully use the existing RA overlay system for applications like displaying arcade game bezels or Vectrex cover overlay sheets, it has limitations that prevent some games with such artwork from being fully emulated.
It is possible to emulate this integral artwork within cores, but doing so requires cores to pre-scale video in order to make use of high-resolution artwork files, negating many of the video-related benefits of libretro-based emulation.
Add a non-interactive, 2-layer artwork system compatible with the MAME artwork format, inspired by but distinct from the existing RetroArch Overlay/Control system.
- Layer 0 - A “backdrop” or “underlay” image that appears “beneath” the emulated video for Arcade and Handheld systems.
- Layer 1 an image that displays “on top” of the emulated video and can be used for bezels and overlays as with Vectrex that are superimposed on the video