How to add a "desktop" emulator to EmulationStation/RetroPie via emulators.cfg?

[RevolutionFlat]

Hardware: AtomicPi

OS: Xubuntu

Software: RetroPie+Emulation Staiton/ MAME 0.22

Have a game that runs fantastic on desktop installed version of Mame, but has various issues with lr-mame2003/10/16. The disk only has 16GB, and even after freeing up 4.9GB, I can't build the experimental MAME package in RetroPie. I can launch the rom from command line perfectly, exits cleanly, love it. I'd like to have it launch from Emulation Station with all the other arcade games. I've tried

mame-desktop = "/usr/games/mame %ROM%"
mame-desktop = "mame %ROM%"
mame-desktop = mame %ROM%

But none of those worked. It shows up as an emulator choice, but crashes back to ES after the launch command.

[mitu]

@revolutionflat Unless the game is only supported only in the latest version of MAME, get the proper ROM version for the emulator - https://retropie.org.uk/docs/Arcade/. You may also try with FBNeo and the ROM in question.

[RevolutionFlat]

@mitu Killer Instinct 1/2, this is my last item before calling this bartop complete. mame2003 version of the rom runs like crap, mame2010/2016 versions run great but you can't map player 2 controls correctly, which seems to be a known issue. Installed desktop Mame, got the working rom version, just need to launch it from EmulationStation that way. There's no way to launch a game from ES with a shell command?

[mitu]

@revolutionflat Use this in emulators.cfg:

mame-desktop = mame %BASENAME%

but make sure you configure MAME's romdir to include your arcade games' romdir, so that MAME finds the game.

[RevolutionFlat]

@mitu Thaaaaaaaat did it! Thanks so much!