[chessx-developer] auto-install of engines on Linux

[H.G. M. <h.g...@hc...>]

Dear ChessX developers,

sorry that I contact you this way; I could not figure out how to use the 
sourceforge trackers to submit a feature request.

I am the current developer of XBoard, and I am trying to set up a system 
for Linux to eleminate the need for users to 'install' engines that are 
already installed by the package-managinging system into the GUIs where 
they want to use them (as is also needed in ChessX through the 
Edit->Preferences->Engine tab). The system is very simple, and I hope 
that ChessX would implement it too.

The idea is that engine packages, as part of their install, would drop a 
small file in a system standard directory reserved for the particular 
protocol the engine speaks. E.g. Stockfish would drop a file

/usr/[local/]share/games/plugins/uci/stockfish.eng

A UCI-supporting GUI would then scan this directory for *.eng files to 
know what UCI engines are currently installed, and from the modify date 
of the file it could see when it was installed. As it also knows the 
modify date of its own settings file that contains its engine list, it 
can know if the engine is newly installed or has been seen before. If it 
is new, it can add it to the list (possibly under control of a user 
option to switch such auto-installs on or off).

To add it to its engine list, it would of course need to have some info 
that normally would be provided by the user that installs it. Such as 
engine startup command (possibly including command-line arguments), and 
the engine directory. (It would already know the engine is UCI, or it 
would not have been in that folder.) This info comes from the contents 
of the .eng file, which (for now) is just 3 lines:

plugin spec 0.0
stockfish
chess,chess960

The first line providing some version number that identifies the file 
format (so that in the future it can easily be extended with more info), 
the second line being the engine startup command to run it in the 
applicable protocol, and the third line what games/variants it can play 
(for now only chess and chess960 are defined). A GUI that only supports 
Chess would obviously have to ignore any engine that does not list 
"chess" on the third line.

For engines that have to run in a specific directory a cd command to 
that directory would be prefixed to its startup command on the second 
line, like

cd ENGINEDIR;ENGINECOMMAND

This should provide the GUI with some minimal information needed to 
append the engine to its engine list. I hope to extend the standard in 
the future by also listing other info that could be relevant for the 
GUI, e.g. known non-compliancies with the protocol for which the GUI 
might have work-around options that could correct it. (E.g. when an 
engine reports scores with the wrong sign when playing black.)

For XBoard protocol (CECP) the corresponding directory would be

/usr/[local/]share/games/plugins/xboard/

Would you be willing to equip ChessX with such an auto-install system? 
The incentive for engine authors to adopt this system will be 
proportional to the number of GUI's that do so, and vice versa. So I am 
trying to collect some critical mass to get it off the ground.

Kindest regards,
H.G.Muller