ThatMinecraftLauncher/lib/launcher/python/mchandler.py

import os

# java -Xmx$RAM$ -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M -Djava.library.path=$NATIVES$ -cp $LIBRARIES$ net.minecraft.launchwrapper.Launch --username $USERNAME$ --version 1.7.10-Forge10.13.4.1614-1.7.10 --gameDir $GAMEDIR$ --assetsDir $ASSETS$ --assetIndex 1.7.10 --uuid $UUID$ --accessToken $ACCESSTOKEN$ --userProperties {} --userType mojang --width $WINDOWWIDTH$ --height $WINDOWHEIGHT$ --tweakClass cpw.mods.fml.common.launcher.FMLTweaker
# $RAM$ the amount of RAM with postfix (k, M, G ...)
# $WINDOWWIDTH$, $WINDOWHEIGHT$ window width and height in pixels without the WM’s decoration
# $USERNAME$ the username as shown in-game
# $UUID$ the player’s uuid
# $ACCESSTOKEN$ a valid accessToken
# $NATIVES$ the directory containing the natives
# $LIBRARIES$ a colon-separated (semicolon-separated on Windowze) list of library jars
# $GAMEDIR$ the game directory IMPORTANT! Change the cwd to that directory before launch. Some mods are coded to find the standard paths by using the cwd.
# $ASSETS$ the directory containing the assets
game_properties = {
    "window width": "1366",
    "window height": "768",
    "ram": autoram(),
    "username": None,
    "uuid": None,
    "access token": None,
    "native directory": "lib/natives",
    "library directory": "lib/jar", # will be transformed by the launch function
    "asset directory": "res",
    "game directory": "run",
    "java executable": "java"}

command = None

full_command = None

def autoram():
    return "4G"
    # TODO: detect available RAM

def launch():
    global command
    if command is None:
        return 1
        # TODO: Raise an exception
    return os.system(command)

def set_parameter(parameter, value):
    global game_propertoies
    game_properties[parameter] = value
    build_full_command()

def build_full_command():
    global game_properties
    global command
    global full_command
    # TODO: implement

def set_command(minecraft_command):
    global command
    command = minecraft_command
    build_full_command()