3.2 Invoking chickadee bundle

Distributing games is difficult. While Chickadee games are free software, it would be far too burdensome on the player to ask them to compile a game from source in order to try it out. Many potential players will simply not even try. Players expect to be able to download a compressed archive, extract it, and play. If there are any more steps than that then the chances of the game being played drop dramatically. If you can’t beat ’em, join ’em. The chickadee bundle tool creates redistributable binary bundles by combining the game code and assets with shared libraries and executables from the host operating system.

Bundling is currently only supported on Linux. In the future, it may be possible to bundle on MacOS. Patches very much welcome for that.

It should be noted that bundling is a problematic way to distribute software. All of the libraries that the bundled application includes are separated from the distribution that was so carefully making sure that they stay up-to-date with regard to security patches. The bundled libraries are frozen in time, vulnerabilities and all. Unfortunately, the release model used by the most popular distributions, while wonderful for stable, mature software, does not fit the needs of game distribution at all. So, we compromise, knowing that most games are only played for only a short amount of time before being disposed. Perhaps, in time, the Linux world will shift to using more robust package management solutions such as GNU Guix which support long-term maintenance of stable software as well as the “fire and forget” nature of game releases. And maybe a game made with Chickadee will become so popular that major distributions decide to package it, but let’s get back to reality.

To get started with bundling, simply add a bundle.scm file to the root of the project directory. It could look something like this:

'((asset-directories . ("images" "models"))
  (bundle-name . "the-legend-of-emacs-1.0")
  (code . "the-legend-of-emacs.scm")
  (launcher-name . "the-legend-of-emacs"))

To create the bundle, simply run chickadee bundle. Upon success, the file the-legend-of-emacs-1.0.tar.gz would be created in the current directory.

To maximize the chances that the bundle will work on someone else’s computer, it’s best to build on the oldest supported Linux distribution available. As of this writing, Ubuntu 18.04 LTS is a good choice.

In addition to including system libraries and executables, chickadee bundle also includes the compiled Guile bytecode (the .go files) for all modules used by the game. The module source files are not included, so it’s critical that all of the modules used by the game have been compiled.

Available options:

• asset-directories

  A list of directories that hold static game assets such as images or audio. Files in these directories will be copied into the bundle archive.

• binary-directories

  A list of directories to search for system binaries, such as guile. By default, /usr/bin is searched.

• bundle-name

  The name of the bundle archive. By default, the name is "chickadee-bundle".

• launcher-name

  The name of the launcher script. By default, the name is "launch-game".

• libraries

  A list of shared libraries to include in the bundle. By default, all of the libraries necessary for running Guile, Guile-SDL2, and Chickadee are included. This list is compatible with the names given to the libraries on Ubuntu, which may be different than on other distributions. In such cases, this list will need to be customized. See below for more information on the %default-config variable that can be of help.

• library-directories

  A list of directories to search for system shared libraries. By default, the list contains common directories used by most distributions.

• method

  The method by which the game is launched. Can be either play or manual. The default is play, which means that chickadee play will be used to launch the game. For games that do not use chickadee play, opting to start the game loop on their own, the manual method should be used.

• play-args

  A list of command line arguments to pass to chickadee play. Only used when the method option is set to play.

Default configuration options, such as the list of C shared libaries, can be found in the %default-config variable. This way they can be programatically modified, if necessary.

Variable: %default-config

An association list of default configuration options.