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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

Installation

Wheels are available on linux, windows and macos for python 3.6, 3.7, 3.8 and 3.9:

$ pip3 install gambaterm

Usage and arguments

Usage:

usage: gambaterm [-h] [--input-file INPUT_FILE] [--frame-advance FRAME_ADVANCE] [--break-after BREAK_AFTER] [--speed-factor SPEED_FACTOR] [--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-factor SPEED_FACTOR, --sf SPEED_FACTOR

    Speed factor to apply to the emulation (default is 1.0 corresponding to 60 FPS)

  • --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)

SSH server

It is possible to serve the emulation though SSH, although clients won't be able to send input to the emulator without an X server and the ssh -X option. Use gambaterm-ssh --help for more information.

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.

  • 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 frames happen during screen transitions of two detailed scenes.

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

Linux Status Colors Unicode rendering Performance Comments
Gnome terminal Excellent 24-bit colors Good 60 FPS
Terminator Excellent 24-bit colors Good 60 FPS
Kitty Excellent 24-bit colors Good 60 FPS
XTerm Good 24-bit colors Good 60 FPS No resize shortcuts
Termit Ok 24-bit colors Good 60 FPS No window title
Rxvt Ok 256 colors Good 60 FPS No resize shortcuts
Mlterm Ok 24-bit colors Light misalignments 60 FPS No resize shortcuts
Terminology Ok 24-bit colors Possible misalignments 30 FPS Weird colors

About MacOS:

MacOS Status Colors Unicode rendering Performance Comments
iTerm2 Good 24-bit colors Good 30 FPS
Terminal Unplayable 256 colors Misalignments 20 FPS

About Windows:

Windows Status Colors Unicode rendering Performance Comments
Windows terminal Unpleasant 24-bit colors Good 30 FPS Buggy display
Cmder Unplayable 24-bit colors Good 2 FPS No window title
Terminus Unplayable 24-bit colors Misalignments 10 FPS
Command prompt Broken N/A N/A N/A No ANSI code support
Git bash Broken N/A N/A N/A Doesn't work with winpty

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 Controller
Directions Arrows Left hat / Left stick
A F / V / Space Button 0 / Button 3
B D / C / Alt Button 1 / Button 2
Start Right Ctrl / Enter Button 7
Select Right Shift / Delete Button 6

Key releases, which are usually mandatory to play games, cannot be detected through stdin. It is then required to access the window system to get access to the key presses. There are a couple of problems with that:

  • It can be hard to detect the window corresponding to the terminal. With X11, the best solution is to look for the current focused window. For other systems, the fallback solution is to use global hotkeys.

  • It only works through SSH for clients with X servers using ssh -X, meaning it requires Windows and MacOS users to run an X server. Moreover, it's a bad idea to connect with -X to an untrusted server.

  • Additional permissions might be required to access the window system, especially on MacOS (see this guide)

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:

Contact

Vincent Michel