Howto:Creating a simple modding framework

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See also Howto:Create a custom version of FlightGear.

Directory Structure

Mods should be using their own directory structure, resembling $FG_ROOT (the base package), e.g.:

• Aircraft
• GUI
• Textures
• Sounds
• Nasal

etc

Requirements

• register hooks to invoke callbacks for specific simulator/addon events
• mutual dependencies

Versioning

See FlightGear Version Check for the main article about this subject.

Proof of Concept

The following snippet of code assumes that you put it into $FG_ROOT/Nasal/mod/mod.nas In addition, you need to add a folder to $FG_ROOT named Mods, beneath this folder you can add other folders - with each folder being treated as a separate "mod".

##
# $FG_ROOT/Nasal/mod/loader.nas

var fgroot = getprop("/sim/fg-root");
var modFolder = fgroot ~ '/'~ getprop('/sim/modding/mod-directory','Mods/');
# http://wiki.flightgear.org/Nasal_library#directory.28.29
var modDirectories = directory( modFolder );

# debug.dump( modDirectories );

foreach(var mod; modDirectories) {
print("Mod directory found:", mod);
}

## invoke:
# init code
# setup  code
# loading code
# clean up code