game-data-packager's Gtk launcher stub
======================================

Here are some design notes about the Gtk game launcher.

Requirements
------------

All of these are already implemented, and should be kept.

* Written in a high-level language (not a shell script with Zenity or
  xdialog)
  - complex shell scripts are a pain to keep maintainable

* All logic is in `game-data-packager.deb` or a future
  `game-data-packager-runtime.deb`, not in the .deb that g-d-p produces
  - the logic might have bugs which we want to fix
  - we can rely on being able to update g-d-p itself via normal Debian
    mechanisms
  - we cannot rely on being able to update anything in a g-d-p-generated
    .deb

* Has a GUI
  - games are often run from menu systems

* Can check whether a representative sample of required files are present
  - some games' data sets have non-obvious tangles of dependencies

* Each user is prompted before running a binary-only game like Unreal
  so they can choose to not run it
  - this is per-user so that users can choose to run all binary-only
    games as uid "jbloggs-games" or something, and protect their
    (potentially root-equivalent) normal uid "jbloggs" from attacks
    via compromised games

* The launcher does not `chdir()` or manipulate `LD_LIBRARY_PATH` until the
  binary-only game is actually run, and the `.desktop` file does not have
  to use `WorkingDirectory=`
  - again, this is to protect individual uids from being attacked via a
    compromised game that they accidentally run from a menu, even if `.`
    is already (unwisely) on a search path

* Optionally constructs a symbolic link farm from one or more system-wide
  search directories
  - this is required for Unreal 1

* If constructing a symlink farm, can copy selected files instead of
  linking them
  - this is required for `*.ini` in Unreal 1

* Games can ship their own proprietary icons which will be used by our
  .desktop files
  - we don't have a Free reinterpretation of the logo for all games

"Nice to have"
--------------

All of these are already implemented, and it would be nice to keep them.

* Game metadata is also in `g-d-p.deb` or `g-d-p-runtime.deb`,
  so we can fix its bugs
  - As currently implemented, it's in an extra section in
    /usr/share/games/g-d-p/unreal-gold.desktop
    or similar. It isn't clear whether this is the right solution.

* The game only installs proprietary files that we cannot fix anyway,
  and symbolic links to stable paths provided by g-d-p or a separate
  game engine like ioquake3
  - `/usr/games/unreal-gold` -> `/usr/share/games/g-d-p-runtime/gdp-launcher`
  - `/usr/share/applications/unreal-gold.desktop` ->
    `/usr/share/games/g-d-p-runtime/unreal-gold.desktop`

* Errors while launching the game are displayed in the GUI

* Does not import from `game_data_packager` and does not rely
  on the YAML/JSON, or only relies on a defined subset (tbd)
  - this means we can consider splitting out
    `game-data-packager-runtime.deb` in future

* GUI is done with a modern toolkit that supports Wayland, etc.,
  and has nice Python bindings
  - implementation detail: it's currently Gtk 3

* freedesktop.org basedir compliant
  - uses `XDG_DATA_HOME`, etc., for games that do not already have a
    well-established dot-directory

* Implementation does not entirely rule out being able to install game data
  "for just me" while unprivileged
  - this may seem rather backwards, but there's some value in having
    a tool like g-d-p shared between multiple games instead of each game
    inventing its own

TODO
----

* Ability to make e.g. `~/.loki/ut` a symlink to e.g. `$XDG_DATA_HOME/ut99`
  if the former does not already exist?
  - we would need to be prepared to fall back to `~/.loki/ut` being a real
    directory, though
