Callbacks on state changes #6

Activity

1. HexDecimal

   added

   enhancementNew feature or requestNew feature or request

   on Jun 28, 2023
2. HexDecimal

   added 3 commits that reference this issue on Jul 31, 2023

   Add callback for component changes

   ...

   4a7faf1

   Add callback for component changes

   ...

   e17c313

   Add callback for component changes

   ...

   c779940
3. HexDecimal

   self-assigned this

   on Aug 2, 2023
4. HexDecimal commented on Oct 7, 2023

   

   HexDecimal

   on Oct 7, 2023

   Last edited by HexDecimal

   OwnerAuthor

   More actions

   Note that tcod.ecs.callbacks.register_component_changed is implemented in the current releases. This can already be used for some tricks such as tracking the spatial position of entities dynamically, such as with the following example:

   @attrs.define(frozen=True)  # Class is frozen to ensure that a changed value is announced
   class Position:
       """Tile position of an entity."""
       x: int
       y: int
   
   
   @attrs.define(frozen=True)
   class MapChunkPosition:
       """Map chunk index of an entity."""
       x: int
       y: int
   
   
   CHUNK_SIZE = 32
   
   @tcod.ecs.callbacks.register_component_changed(component=Position)
   def on_position_changed(entity: Entity, old: Position | None, new: Position | None) -> None:
       """Track the Position component as a tag in entities. Update the map chunk position."""
       if old == new:
           return  # Reduce cache invalidation by not adding and removing the same tag
       if old is not None:
           entity.tags.remove(old)
       if new is not None:
           entity.tags.add(new)
           entity.components[MapChunkPosition] = MapChunkPosition(new.x // CHUNK_SIZE , new.y // CHUNK_SIZE)
       else:  # new is None
           del entity.components[MapChunkPosition]
   
   @tcod.ecs.callbacks.register_component_changed(component=MapChunkPosition)
   def on_chunk_position_changed(entity: Entity, old: MapChunkPosition | None, new: MapChunkPosition | None) -> None:
       """Track the MapChunkPosition component as a tag in entities."""
       if old == new:
           return
       if old is not None:
           entity.tags.remove(old)
       if new is not None:
           entity.tags.add(new)

   With this setup you can query entities by an exact or approximate position.

   world.Q.all_of(tags=[Position(0, 0)])  # Query all entities at an exact position.
   world.Q.all_of(tags=[MapChunkPosition(0, 0)])  # Query all entities in a more general area.
5. HexDecimal

   removed their assignment

   on Oct 19, 2026