Mods that wish to provide callbacks to events or provide new subsystems and/or components can do so through mod registration.
Registration happens when a world is selected or a new world is created. Only the mods that are enabled for the world will be registered.
Use registration_finished() event to know when registration has finished.
Adding registration is easily done by creating a file such as mods/mymod/registration.py and inside of it provide a register() function.
It is important to be sure to fully unregister callbacks that you add during registration.
This can be achieved by game.onUnregistration.listen(systemUnregistration) and of course providing a systemUnregistration().
This is all setup and ready to use in the mod template.
Below is the core registration file, mods/core/registration.py, as an example.
from core.environment.sky import SkyRenderable
import core.achievement
import core.biome
import core.component.registration
import core.effect
import core.events
import core.item.armor.attribute
import core.monster.affix
import core.monster.boss
import core.system.registration
import core.terraform
import core.terraform.world
import core.terraform.dream_realm
import core.terraform.forgotten_shrine
import core.terraform.horde_realm
import core.terraform.mighty_forest
import core.terraform.throne_room
import core.hit_tile
from siege import game
from siege.network import NetworkManager
def register():
game.onUnregistration.listen(systemUnregistration)
game.events['world_loaded'].listen(SkyRenderable.handleWorldLoaded)
game.events['registration_finished'].listen(core.terraform.world.addTemplate)
game.events['registration_finished'].listen(core.terraform.forgotten_shrine.addTemplate)
game.events['registration_finished'].listen(core.terraform.dream_realm.addTemplate)
game.events['registration_finished'].listen(core.terraform.horde_realm.addTemplate)
game.events['registration_finished'].listen(core.terraform.mighty_forest.addTemplate)
game.events['registration_finished'].listen(core.terraform.throne_room.addTemplate)
core.achievement.register()
core.biome.register()
core.component.registration.register()
core.effect.register()
core.events.register()
core.item.armor.attribute.register()
core.monster.affix.register()
core.monster.boss.register()
core.system.registration.register()
core.terraform.register()
if NetworkManager.isHost():
core.hit_tile.register()
def systemUnregistration():
game.onUnregistration.remove(systemUnregistration)
game.events['world_loaded'].remove(SkyRenderable.handleWorldLoaded)
game.events['registration_finished'].remove(core.terraform.world.addTemplate)
game.events['registration_finished'].remove(core.terraform.forgotten_shrine.addTemplate)
game.events['registration_finished'].remove(core.terraform.dream_realm.addTemplate)
game.events['registration_finished'].remove(core.terraform.horde_realm.addTemplate)
game.events['registration_finished'].remove(core.terraform.mighty_forest.addTemplate)
game.events['registration_finished'].remove(core.terraform.throne_room.addTemplate)
core.achievement.unregister()
core.biome.unregister()
core.events.unregister()
core.monster.boss.unregister()
core.system.registration.unregister()
core.terraform.unregister()
if NetworkManager.isHost():
core.hit_tile.unregister()
return True