Script Configuration

Scripts are a second large part of game objects which cannot be defined purely in yaml, you’d likely use python for that instead. to make things easy we’ll be loading scripts from a python “package” instead (i.e. an __init__.py file is required). For creating scripts see Scripts.

For this example i will be showing two ways scripts get loaded by the builtin ScriptLoader.

scripts:
   loader: ScriptLoader
   config: scripts
   registry: ScriptRegistry

scripts
├── __init__.py
└── move_script.py

Optional content of __init__.py

from pg_engine.base_scripts import OOBCleanup

Content of move_script.py

import pygame

from pg_engine.core import TScript
from pg_engine.systems import (
    EventListener,
    Scope,
    listen,
)

class MoveScript(TScript, EventListener):
    __exports__ = 'move_script'

    def __init__(self, step: int, **kw):
        super().__init__(**kw)
        self.step = step

    @listen(event_type=pygame.KEYDOWN, scope=Scope.BROADCAST)
    def listen_movement(self, event: pygame.event.Event) -> None:
        match event.key:
            case pygame.K_LEFT:
                self.source.transform.move((-self.step, 0))
            case pygame.K_RIGHT:
                self.source.transform.move((self.step, 0))
            case pygame.K_UP:
                self.source.transform.move((0, -self.step))
            case pygame.K_DOWN:
                self.source.transform.move((0, self.step))

__all__ = [
    'MoveScript',
]

The first option is loading scripts directly from the __init__.py file, a good example is if you want to make use of oob_cleanup, a script used to clean up gameobjects that are considered out of bounds and should be destroyed.

the second method is providing script files as is in the scripts directory (config key) or subpackages thereof. Up above we defined a script MoveScript which we wish to use in our game. A problem that could occur here is that we are extending off of another script. Here this is not the case with EventListener as it is technically not a script but could be the case with the import some other script which we do not want to export into our game. in situations like this __all__ can be used to filter out which scripts should be made available for exports.

Note

only scripts with __exports__ set will be exported

Warning

Use __init__.py only to load scripts from external sources into your game. If scripts are already being provided in the scripts directory this will cause PG_Engine to attempt to load the scripts twice.