[LUA] detect difference between a game start and restart?

[Jakobud]

From what I understand you would typically use emu.add_machine_reset_notifier(callback) to make your LUA plugin do something when a game starts or is restarted.

However I recently came across a MAME rom: zwackery

I noticed that this game has a startup procedure like most games (checking roms, sound, etc). It lasts for maybe 10+ seconds or so.

But if you hit reset (F3) for this game, it restarts the game but the startup sequence is shortened to only 1-2 seconds. It appears to skip a lot of the sequence from when you start the game initially.

Are these two different events in LUA? the emu.add_machine_reset_notifier(callback) seems to happen for both cases, but there are clearly different things happening here.

There are probably other games with this behavior but this is the first I've noticed.

[holub]

Not sure about precise names but initial startup is hard reset which calls "start+reset" and can be reinitiated with Shift+F3
Soft reset is just "reset" which is F3

[Jakobud]

Thank you but I'm asking about the LUA API.

[holub]

https://github.com/mamedev/mame/blob/e3907cb6977d19d973b30f08bfaa0501b5ccdb79/src/frontend/mame/luaengine.cpp#L778

[Jakobud]

Okay so emu.register_start(callback) is deprecated and has been replaced with emu.add_machine_reset_notifier(callback). I'm asking specifically about if there is a different notifier for when a game starts vs when it resets and why the reset notifier is triggered for both starts and resets when they appear to do different things in some games.

[rb6502]

MAME has a defined order of operations. When you start up an emulated machine, it first calls "start" on everything, and then it calls "reset" on everything. This is pretty much how all digital hardware works if you think of the "start" as turning the power on. First you apply power, and then some circuit automatically resets (at least) the CPU so that it can start running in a known state.

[Jakobud]

Okay I think I understand that. Does the LUA api differentiate between the 2 somehow?

Try running the rom zwackery. Wait for it to go through the boot sequence. Then pretty reset (F3) and see the difference. Do the LUA notifiers differentiate between these 2 behaviors?

[cuavas]

There currently isn’t a way to get a callback on start. emu.register_start was named misleadingly – it was called on reset. It’s something I’d like to add, but I don’t want to go changing the callbacks without thinking it through properly – I don’t want to create churn, particularly when it might affect core classes like the running machine and the externally visible Lua API.

[Jakobud]

Thank you for the insight and brilliant work you do!

[galibert]

Perhaps an extra bool parameter to the reset callback? Lua is very permissive there.

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[Jakobud]

Can you elaborate on what you mean by this?

I was also thinking about just setting a bool variable in the plugin that gets toggled off when the game exits. I would set it true when the game starts and then if I reset (F3) then it would still be true and know that it's a soft reset. However that wouldn't help with the hard reset as it would still be true I think. I'll experiment with this.

[Jakobud]

Okay I found a workaround to this.

local running = false

Then at start of my emu.add_machine_reset_notifier function:

if not running then
  print("start or hard reset detected")
  running = true
else
  print("soft reset detected")
end

And then in my emu.add_machine_stop_notifier function:

running = false

This appears to accurately differentiate between a start/hard reset and a soft reset.