gambaterm 1.3.1

A terminal frontend for gambatte game boy color emulator

gambatte-terminal

A terminal front-end for gambatte, the gameboy color emulator.

It supports:

• 16 colors, 256 colors and 24-bit colors terminal
• Playing audio from the emulator
• Using TAS input files as game input
• Using keyboard presses as game input

Quickstart

Using uvx:

$ uvx gambaterm myrom.gbc

Installation

Wheels are available on linux, windows and macos for python 3.10 to 3.14:

$ pip3 install gambaterm

Usage and arguments

Usage:

usage: gambaterm [-h] [--input-file INPUT_FILE] [--frame-advance FRAME_ADVANCE]
                 [--break-after BREAK_AFTER] [--speed SPEED] [--force-gameboy]
                 [--skip-inputs SKIP_INPUTS] [--cpr-sync] [--disable-audio]
                 [--color-mode COLOR_MODE]
                 ROM

Positional arguments:

• ROM

  Path to a GB or GBC rom file

Optional arguments:

• --input-file INPUT_FILE, -i INPUT_FILE

  Path to a bizhawk BK2 input file

• --frame-advance FRAME_ADVANCE, --fa FRAME_ADVANCE

  Number of frames to run before displaying the next one (default is 1)

• --break-after BREAK_AFTER, --ba BREAK_AFTER

  Number of frames to run before forcing the emulator to stop (doesn't stop by default)

• --speed SPEED, -s SPEED

  Control the execution speed (default is 1.0)

• --force-gameboy, --fg

  Force the emulator to treat the rom as a GB file

• --skip-inputs SKIP_INPUTS, --si SKIP_INPUTS

  Number of frame inputs to skip in order to compensate for the lack of BIOS (default is 188)

• --cpr-sync, --cs

  Use CPR synchronization to prevent video buffering

• --enable-controller, --ec

  Enable game controller support

• --disable-audio, --da

  Disable audio entirely

• --color-mode COLOR_MODE, -c COLOR_MODE

  Force a color mode (1: 4 greyscale colors, 2: 16 colors, 3: 256 colors, 4: 24-bit colors) Note: the color mode can be cycled at runtime by pressing the Tab key, which is useful for testing the different color modes supported by the terminal.

SSH server

It is possible to serve the emulation through SSH. Clients must use a terminal that supports the kitty keyboard protocol, or use X11 forwarding (ssh -X) as a fallback. Use gambaterm-ssh --help for more information. 24-bit color is always assumed over SSH. Audio is not available over SSH.

# Serve `myrom.gbc` locally on port 8022, disabling authentication for local testing
# Note: an SSH host key is automatically generated on the first run
$ gambaterm-ssh --no-auth myrom.gbc
Generating SSH host key at ~/.config/gambaterm/ssh_host_key...
Authentication disabled (no password nor public key required)
Running SSH server on 127.0.0.1:8022...

# Listen on all interfaces, using a global password as authentication method
$ gambaterm-ssh --password mypassword --bind 0.0.0.0 --port 8022 myrom.gbc
Authentication methods:
- Global password
- Public keys from: /home/user/.ssh/id_rsa.pub
Running SSH server on 0.0.0.0:8022...

Connect with ssh client:

$ ssh localhost -p 8022

Telnet server

The emulator can also be served over telnet, requiring no authentication or SSH keys:

$ gambaterm-telnet myrom.gbc
$ gambaterm-telnet --bind 0.0.0.0 --port 8023 myrom.gbc  # listen on all interfaces

Connect with any telnet client:

$ telnet localhost 8023

Clients must use a terminal that supports the kitty keyboard protocol -- connections without it are rejected. Use --max-players N to limit concurrent connections. 24-bit color is always assumed. Audio is not available over telnet.

Terminal support

Not all terminals will actually offer a pleasant experience. The main criteria are:

• Support for basic ANSI codes (VT100) More specifically setting background/foreground colors and moving cursor (absolute and relative). Those are usually supported.

• Support for at least 256 colors Those are usually supported. 16 colors also works but it doesn't look too good. In this case, it might be better to use greyscale colors using --force-gameboy or --color-mode=1.

• Support for UTF-8 and good rendering of unicode block elements More specifically the following characters ▄ █ ▀. Also, the alignement might be off (e.g small spaces between pixels) This is not always well supported.

• Support for the kitty keyboard protocol This is mandatory if you're using Wayland, and recommended on every other platforms. In the case where the kitty keyboard protocol is not detected by gambaterm, the following fallbacks are implemented:

  • Linux: uses X11 through python-xlib
  • Macos: uses pynput (it requires granting specific authorizations to the terminal app)
  • Windows: uses pynput (the key presses are detected even if the terminal windows is not focused) It is also mandatory when connecting to a gambaterm SSH server.

• Good rendering performance The terminal has to be able to process about 500KB of requests per seconds for a smooth rendering of "intense" frames. Typically, the most intense bursts happen during screen transitions of two detailed scenes.

The table below sums up my findings when I tried the most common terminal emulators. Here's about linux:

Linux	Status	Colors	Unicode rendering	Kitty keyboard protocol	Performance	Comments
Ghostty	Excellent	24-bit colors	Good	Yes	60 FPS
Kitty	Excellent	24-bit colors	Good	Yes	60 FPS
foot	Excellent	24-bit colors	Good	Yes	60 FPS
Rio	Excellent	24-bit colors	Good	Yes	60 FPS
Contour	Excellent	24-bit colors	Good	Yes	60 FPS	Download latest for kitty support
Alacritty	Good	24-bit colors	Good	No*	60 FPS	*Fails kitty detection due to reported bug
Konsole	Good	24-bit colors	Good	No	60 FPS
Gnome terminal	Good	24-bit colors	Good	No	60 FPS
Terminator	Good	24-bit colors	Good	No	60 FPS
XTerm	Good	24-bit colors	Good	No	60 FPS	Ctrl+Right click to resize, "Unreadable" locks up XTerm
Rxvt	Good	24-bit colors	Good	No	60 FPS	No resize shortcuts
Terminology	Good	24-bit colors	Light misalignments	No	60 FPS	Font sizes under ~9pt create horizontal line artifacts
Termit	Ok	24-bit colors	Good	No	60 FPS	No window title
Mlterm	Ok	24-bit colors	Light misalignments	No	60 FPS	No resize shortcuts

About MacOS:

MacOS	Status	Colors	Unicode rendering	Kitty keyboard protocol	Performance	Comments
iTerm2	Excellent	24-bit colors	Good	Yes	60 FPS
Terminal.app	Bad	24-bit colors	Bad--adjust font spacing!	No	30 FPS	A bit jittery

About Windows:

Windows	Status	Colors	Unicode rendering	Kitty keyboard protocol	Performance	Comments
Windows terminal	Excellent	24-bit colors	Good	Yes	60 FPS	Download latest for kitty support)
Cmder	Unplayable	24-bit colors	Good	Yes	2 FPS	No window title
Terminus	Unplayable	24-bit colors	Misalignments	No	10 FPS
Command prompt	Bad	24-bit colors	Good	No	1 FPS	Slow/Unresponsive
Git bash (mingw64)	Ok	24-bit colors	Good	No	N/A

Terminals without Kitty keyboard protocol require X11 to play locally, or X11 forwarding to use over SSH.

Terminal size

The emulator uses a single character on screen to display two vertically aligned pixels, like so ▄▀. The gameboy being 160 pixels wide over 144 pixels high, you'll need your terminal to be at least 160 characters wide over 72 characters high to display the entire screen. Setting the terminal to full screen is usually enough but you might want to tweak the character size, typically using the ctrl - / ctrl + or ctrl wheel shortcuts.

Keyboard, game controller and file inputs

Keyboard controls are enabled by default, while game controller controls have to be enabled using --enable-controller or --ec.

The key bindings are not configurable at the moment:

Buttons	Keyboard with arrows	Keyboard with WASD	Controller
Directions	Arrows	W A S D	Left hat / Left stick
A	X	K	Button 0 / Button 3
B	Z	J	Button 1 / Button 2
Start	Enter	Enter	Button 7
Select	Right Shift	Right Shift	Button 6

Save state commands	Keyboard
Select slot	0 to 9
Save state	[
Load state	]

Since gambaterm detects physical key presses, this table indicates the keys as seen on a QWERTY keyboard. In particular, AZERTY or Bépo user won't need to change their keyboard layout in order to play. It is also possible to use a bizhawk BK2 input file to play tool-assisted speedruns using the --input-file (or -i) option.

Motivation

To be honest there is no actual reason to use this gameboy emulator, other than you might find it fun or interesting. The motivation behind this project is simply to push the idea of running a video game console emulator in a terminal as far as possible. It seems like there has been a similar attempt that used a different approach for displaying the video stream. In any case I'm quite satisfied with this project, and also a bit surprised that I could push it to the point where playing games is actually enjoyable. In particular, I've been able to complete The Bouncing Ball at 60 FPS in XTerm, and I'm now looking forward to playing more homebrew games :)

Dependencies

Here is the list of the dependencies used in this project, all great open source libraries:

• gambatte-core - Gameboy emulation
• Cython - Binding to gambatte C++ API, and fast video frame conversion
• blessed - Cross-platform terminal handling and kitty keyboard protocol support
• samplerate - Resampling the audio stream
• miniaudio - Playing the audio stream
• xlib/pynput - Getting keyboard inputs
• pygame - Getting game controller inputs
• asyncssh - Running the SSH server
• telnetlib3 - Running the telnet server

Contact

Vincent Michel