Bouncing from Kodi to EmulationStation, and back

Update:

----
As pointed out on the RetroPie forum, just add the loop in autostart.sh, duh: I searched for a while before writing this thing and if I'd seen anyone mention that I'd have just done that instead.

while :
do
kodi
emulationstation
done

I also think it makes a more sensible default for RetroPie to implement. That's all I actually wanted at the start.

However...

Now I've added Features. I can hijack my loop and add one-off commands.

So now there's a Desktop button in my Kodi main menu that will touch a file to cause the loop to gracefully exit Kodi and send me to a desktop session. When I leave the desktop session, it takes me back to Kodi. So that's pretty goddamn convenient.

-----

Because if there's one thing I love, it's having to sysadmin my TV.

Like most reasonable people I use a Kodi mediacenter to run my TV. Lately this has been on a Raspberry Pi 4 running RetroPie. Generally people boot RetroPie into EmulationStation and use it as an emulator, such as on an arcade cabinet. I'm also one of those people.

But in this case I primarily use the TV to watch TV shows and movies, but also want to run console games, so I upgraded to a better RPi and migrated from LibreElec to RetroPie.

RetroPie lets you choose whether to boot into EmulationStation or Kodi, which is fine, and the idea is that if you quit Kodi, it loads ES so you can play games. That works fine. Once. The trouble is in going the other way. If you quit EmulationStation, you exit to a shell. If you run Kodi from within the Ports menu in EmulationStation, well, now you're running both ES and Kodi. This also changes the behavior the next time you quit Kodi to play a game. You end up back in the Ports menu with Kodi highlighted, because ES never quit.

So, that's what I fixed.

The way the RetroPie tool works is they create a script at /opt/retropie/configs/all/autostart.sh. If you have Kodi booting first, it will have two lines:

kodi-standalone
emulationstation.

That script gets run at login time for the pi user. Basically it runs Kodi, and autostart.sh is still running. When Kodi exits, it runs ES and autostart.sh exits. If you wanted to you could just put 1000 lines of:

kodi-standalone
emulationstation
kodi-standalone
emulationstation
kodi-standalone
...

However that's ugly, so I kind of daemon-fied it with a bash script of my own that I wanged together in like 10 minutes, and then I launch that through their autostart.sh. I didn't want to replace their script with mine because the RetroPie one could get regenerated with an upgrade or if I hit something in RetroPie-config. It's safer to have their script call mine.

So what I do is I start with whichever application is passed to me in the command line:

autolaunch.sh -f kodi

Then I start an infinite loop and, based on what application the script is called with, it will start the first application. When that app exits, I change the value of the variable so that the next time it loops, it runs the other one:


#! /bin/bash

while getopts f: name
do
  case $name in
    f) fval="$OPTARG";;
    ?) printf "Usage %s: [-f application to start] args\n" $0
    exit 2;;
  esac
done

while :
do
  if [ $fval = kodi ]
  then
    kodi-standalone
    fval="emulationstation"
  elif [ $fval = emulationstation ]
  then
     emulationstation
    fval="kodi"
  fi
done

Downsides and ToDo's:

Obvious downside is that this makes it difficult to get a shell at the console of the machine. However, I can count on one hand the number of times I've had to do that in the last 6 years or so of running my TV from a Raspberry Pi, so I really don't care.

A definite ToDo is to add some level of process control and general safety so I don't somehow end up running a bunch of instances of Kodi and ES. I did test with "Restart Emulationstation", so it would pick up new games, and it seemed to work as expected. It didn't launch another instance of Kodi or anything.

My main ToDo is to have the ability to use more launchers. Basically right now I have a "Games" menu item in my Kodi main menu, I hit it, it just runs the Kodi "Quit" command, which causes ES to start. Same thing in ES, though I'm just quitting it using the context menu at the moment.

I'd like to be able to add a "Desktop Session" button to quit Kodi or ES and launch a desktop with a browser for those very rare times I want a browser on my TV. This would also solve the "can't get a local shell" problem, at least mostly. I could add a "quit to shell" in this way obviously as well. I think the best way to do this is to stop the script as I exit Kodi and restart it with a new starting value, like -f startx. Kind of like if it were a real system daemon.

However I think in my case, since I'm not a very good programmer, I'm going to just bang this out with a file in /var/tmp or somewhere which carries the "Next Command", so rather than update $fval as I am now, I'd check that file and have it read in each loop to set fval. That would allow me to hijack it from outside the loop.

So I'm in Kodi, if I quit, it's going to set $fval to "emulationstation" and load ES. However, if I run a shell script, and /then/ quit or killall kodi-standalone, that shell script can populate /var/tmp/nextcommand or whatever with "startx".

Then, when Kodi quits, it sets $fval to ES, the next loop comes, but instead of just launching ES, we check to see if there's a value in nextcommand. If there is, set $fval to that and run it instead.

Then you'll start an X session, and when that quits, it should take me back to Kodi.

I seem to recall Kodi's internal tools are pretty good, and I can combine "run this external command" with "run this internal 'quit' command" and assign that to a menu "Action". Just need to remember where all that stuff is.