An incomplete, buggy and suboptimal GameBoy emulator written in Go purely for fun. It displays pixels, makes noises and can export GIFs. Hopefully it can also prove remotely informative to anyone wanting to get into emulators!

Disclaimer

All code available here is raw, broken, doesn't follow any specific kind of workflow and isn't guaranteed to work in any way or form.

It might contain blatant errors, awkward workarounds and the occasional profanity in comments or commit messages. Golang at least guarantees that the formatting is somewhat consistent.

Those are the main reasons why this code used to be self-hosted for so long.

Getting Goholint

The easiest way to run Goholint for now is probably to use go get.

go get github.com/lazy-stripes/goholint
$GOPATH/bin/goholint -help

Usage

The emulator ships without any kind of ROM for hopefully obvious reasons. If you want a scrolling logo, the emulator needs a boot ROM it will attempt to read from bin/boot/dmg_rom.bin or whatever path you specify with -boot.

With that taken care of, goholint ‑rom <path> should be enough to see an SDL window potentially displaying some interesting things, or more likely a blank screen, if it doesn't crash first.

(As of 2021, Tetris, Dr. Mario, TMNT and Link's Awakening are actually playable.)

See goholint -help for the full list of supported options, until I write an actual manual for it.

Controls

The default controls are:

Action	Key
A Button	S
B Button	D
Select Button	Backspace
Start Button	Return
Joypad Up	Arrow Up
Joypad Down	Arrow Down
Joypad Left	Arrow Left
Joypad Right	Arrow Right

(It's sort of okay on QWERTY and AZERTY keyboards alike but does make Metroid II awkward to play.)

Goholint also support the following actions:

Action	Key
Quit	CTRL+Q
Screenshot	F12
Start/stop GIF recording	G
Previous palette	Page Up
Next palette	Page Down
Toggle Voice 1	1
Toggle Voice 2	2
Toggle Voice 3	3
Toggle Voice 4	4

All screenshots/GIF files are created in the ~/.goholint/ folder, in the screenshots and gif subfolders, respectively. GIF animations only use the palette that was active when the recording started.

You can customize all controls by modifying the ~/.goholint/config.ini file in your home folder (it should be created automatically if it doesn't exist yet) of by providing your own with -config.

TODO

Fix compatibility bugs (obv.)
Save states
Fast boot (embed end-of-boot state?)
Cheat codes
UI improvements

Acknowledgements

UI font is Press Start 2P Font by codeman38.

The present project only exists thanks to Tomek Rękawek and his fascinating blog article about how relatively easy it was to start implementing a GB emulator. His own emulator, coffee-gb, was a great help and inspiration in the making of this.

I otherwise officially blame @dmuth for retweeting the aforementioned blog post.

Also @balinares for motivating me to make this public. Love you guys! ♥

# Packages