Events

Cross-loader events: register listeners in common code, and CoolCatLib bridges them to each loader's own events. Package: net.ixdarklord.coolcatcore.api.event.v2 (core, common, client).

Warning

api.event.v2 is marked @UnstableApi: event names may still change between releases.

Listening

Every event is an EventInvoker constant on a holder class:

ServerTickEvents.END.register(server -> { /* after every server tick */ });

PlayerEvents.JOIN.register(player -> player.sendSystemMessage(Component.literal("Welcome!")));

// Returning an interrupting result cancels the break.
BlockEvents.BREAK.register((level, pos, state, player) ->
        state.is(Blocks.BEDROCK) ? EventResult.interrupt() : EventResult.pass());

CommandEvents.REGISTER.register((dispatcher, context, selection) ->
        dispatcher.register(Commands.literal("hello").executes(ctx -> 1)));

// Order listeners with phases (FIRST, EARLY, DEFAULT, LATE, LAST).
ServerTickEvents.END.register(EventPhase.LATE, server -> { });

// Events can also be found by their listener type.
EventInvoker.lookup(ServerTickEvents.End.class).register(server -> { });

Your own events

EventInvoker.create makes an event from a functional interface, and combines listeners by the method's return type:

Return type	How listeners run
void	Every listener runs.
EventResult	Until one interrupts (anything but PASS); that result is returned, else PASS.
EventResultHolder<T>	The same, carrying a value.
boolean	Until one returns false.

@FunctionalInterface
public interface ShapeUnlocked { void onUnlocked(ServerPlayer player, Identifier shape); }

public static final EventInvoker<ShapeUnlocked> SHAPE_UNLOCKED = EventInvoker.create(ShapeUnlocked.class);

// Fire it:
SHAPE_UNLOCKED.invoker().onUnlocked(player, shapeId);

For custom combining, use EventInvoker.create(Class<T> type, Function<List<T>, T> combiner).

Built-in events

Common (api.event.v2.common)

Holder	Event	Listener
ServerLifecycleEvents	STARTING, STARTED, STOPPING, STOPPED	(MinecraftServer)
	SYNC_DATA_PACK_CONTENTS	(ServerPlayer player, boolean joined): fires per player on login (joined is true) and for every player after /reload. Send datapack-loaded data to clients here.
ServerTickEvents	START, END	(MinecraftServer)
	START_LEVEL, END_LEVEL	(ServerLevel)
PlayerEvents	JOIN, LEAVE	(ServerPlayer)
	START_TICK, END_TICK	(Player): both sides; check player.level().isClientSide()
EntityEvents	LOAD	(Entity, ServerLevel): spawned or loaded with a chunk, players included
BlockEvents	BREAK	EventResult (ServerLevel, BlockPos, BlockState, ServerPlayer): interrupt to cancel
	PLACED	(Level, BlockPos, BlockState, @Nullable Entity placer)
CommandEvents	REGISTER	(CommandDispatcher<CommandSourceStack>, CommandBuildContext, Commands.CommandSelection)
AttachmentEvents	CHANGING, ADDED, CHANGED, REMOVED, START_TRACKING, STOP_TRACKING, RECEIVED	See Attachments.

Client (api.event.v2.client)

Holder	Event	Listener
ClientTickEvents	START, END	(Minecraft)
ClientPlayerEvents	JOIN	(LocalPlayer)
	LEAVE	(@Nullable LocalPlayer)
ClientGuiEvents	RENDER_HUD	(GuiGraphicsExtractor graphics, DeltaTracker delta): draws over the vanilla HUD every frame
ItemTooltipEvents	MODIFY	(ItemStack, Item.TooltipContext, TooltipFlag, List<Component> lines): the finished lines, name included
ClientCommandEvents	REGISTER	(CommandDispatcher<SharedSuggestionProvider>, CommandBuildContext). Reply with ClientCommandEvents.sendFeedback(component) or sendError(component).

Elsewhere

• Config events (ConfigEvents): see Configs.
• Screen effect events (ScreenEffectEvents, in Canvas): see Canvas Screen Effects.
• Brewing recipes: api.event.v1.server.RegisterBrewingRecipesEvent.EVENT.register(event -> event.getBuilder().addRecipe(input, ingredient, output)), from the older event.v1 API.

Reference

Type	Description
EventInvoker<T>	register(listener), register(EventPhase, listener), unregister(listener), hasListeners(), invoker(), type(); static lookup(Class), create(Class), create(Class, combiner).
EventPhase	FIRST (-2000), EARLY (-1000), DEFAULT (0), LATE (1000), LAST (2000); of(name, order), before(), after().
EventResult	PASS, INTERRUPT, ALLOW (interrupts as true), DENY (interrupts as false); pass(), interrupt(), allow(), deny(), isInterrupt(), isPass(), getAsBoolean().
EventResultHolder<T>	pass(), interrupt(value), allow(value), deny(value); getValue(), getInterrupt(), getAllow(), getDeny(), ifInterrupt, ifAllow, ifDeny, map, flatMap, filter, result().