save state

[jancborchardt]

To be able to actually play the games properly rather than just fiddle around, the game state should be saved. Not sure if internal game save functions can be accessed or if it’s feasible to just always have the latest state changed. The Gameboy Emulator by Grant Galitz seems to do both.

It’s probably best to always automatically save in localStorage/IndexedDB so that people can return to their game. Maybe even use remotestorage so you can change browsers.

[omarduarte]

@bfirsh, I may be able to add this feature given a few hints on which parts of the code need to be changed. Any ideas?

[josephlewis42]

I've got this working over in my repo at https://github.com/josephlewis42/jsnes

[jancborchardt]

@josephlewis42 can you open a pull request then? :)

[josephlewis42]

No problem, just did it!

The save is localstorage though rather than remotestorage.

[lazyxu]

@josephlewis42
I found an error while testing the localstorage function.
below "apply" should be replaced by "call" since s is a json object.

JSNES.Mappers[4].prototype.fromJSON = function(s) {
JSNES.Mappers[0].prototype.fromJSON.apply(this, s);
...
}

[bfirsh]

I've moved the web emulator to a different repository and created an issue for it. Thanks all for your input! bfirsh/jsnes-web#18

[oknoorap]

how to save and load state? any snippet here? @bfirsh

[lazyxu]

I have done this by localStorage, hope this helps you. @oknoorap
save:

try{
    var saveData = JSON.stringify(nes.toJSON());
    localStorage.setItem(romName, saveData);
}catch(oException){
    if(oException.name == 'QuotaExceededError'){
        console.log('localStorage out of memory');
        localStorage.clear();
        localStorage.setItem(calcMD5(rompath), saveData);
    }
}

load:

var saveData = localStorage.getItem(romName);
if( saveData == null ) {
    console.log("nothing to load");
    return;
}
var decodedData = JSON.parse(saveData);
nes.fromJSON(decodedData);

[oknoorap]

I just did that but doesn't works with jsnes-web, load state doesn't overwrite existing canvas

[lazyxu]

Maybe you forgot to run nes.frame() after load state.

Or perhaps bfirsh removed some related code from jsnes to jsnes-web.

Anyway, I successed to do this with the old versions of jsnes

[oknoorap]

okay, will try, I'll post again when succeed

[oknoorap]

@MeteorKL: great, it's succeed (without nes.frame())

[oknoorap]

@MeteorKL After state loaded, I don't think that save state write bytes correctly, this glitch should be a number (score when mario kill mushroom monster)

[lazyxu]

I don't quite understand this glitch should be a number (score when mario kill mushroom monster)
Did you mean that score is not the same as the old one?

[oknoorap]

This glitch graphics

should be a number (score)

[lazyxu]

Did you mean that
the first graphics: after load
the second graphics: before load

[oknoorap]

yep, after load state there was glitchy graphics in the game

[lazyxu]

Maybe you can stop the frame interval brefore save state, and continue it after load.

I guess it is just because you still run the game after saving state.

[oknoorap]

I do this.stop() or

this.frameTimer.stop();
this.speakers.stop();

before save to local storage, it's still has glitch

[lazyxu]

It seems that the second graphics happens after the first graphics. It is pretty confusing and I have no idea about this.
Maybe you can try another rom to see whether this happens again.

[oknoorap]

Pacman doesn't have any trouble with graphics, but after load state, sounds are muted... 😄

[oknoorap]

Mario 2 after load state 😄

[lazyxu]

Interesting bug :)
Maybe there are some mistakes in transforming data in localStorage.
You can compare the JSON string before saving state and after loading state
by saving them to txt and using some tools like vimdiffer.

[oknoorap]

I've modify nes.js by encoding romData to base64 in toJSON function, and decodes back in fromJSON function, it should be the same data... and it's still buggy 😄

[oknoorap]

may be it's related with Tile or ppu issue? can you help me 😭 @MeteorKL, I want to submit PR but I'm too dumb to understand jsnes's code...

[lazyxu]

I'm also on the way to understanding jsnes's code.
Maybe you can show your code to me by your Github or sending mail to me.

[bfirsh]

This is probably because toJSON or fromJSON somewhere is missing some data...

[oknoorap]

@bfirsh personally as developer I want to submit PR but it's too complicated to me to read low level code like yours, I'm sorry I just support you here, good luck, hope this issue will be solved 😄

[oknoorap]

any news related to glitch issue?

[oknoorap]

@bfirsh is this issue still can't be fixed? 😃

[bfirsh]

I don’t have the time to look at it at the moment, but others are very welcome to tackle it! The main issue tracking is here: bfirsh/jsnes-web#18

[Skypow2012]

I want to save data by save the nes.cpu.mem.(So this game state can lower from 1.9MB to 187KB) but in this way. when I load the mem, the frame's background is before background. Is there any method can refresh the background? I try to save the nes.ppu.bgbuffer, nes.ppu.vramMem, do nes.ppu.updatePalettes(), but not work, mayby I have sth wrong. Can anyone help me?
@bfirsh

localStorage.mem = JSON.stringify(nes.cpu.mem); // save
nes.cpu.mem = JSON.parse(localStorage.mem); // load

[JoeMeeks]

@bfirsh, @Skypow2012, @oknoorap, @lazyxu, @josephlewis42, @jancborchardt I have fixed the load via fromJSON in my PR:
#397