Add CreeperSwellEvent

paper-api/src/main/java/io/papermc/paper/event/entity/CreeperSwellEvent.java

@@ -0,0 +1,161 @@
+package io.papermc.paper.event.entity;
+
+import org.bukkit.entity.Creeper;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.entity.EntityEvent;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Fired whenever a creeper's swell level changes.
+ * <p>
+ * If this event is cancelled, the swell change will not be applied, but the client may still render the swell change.
+ */
+@NullMarked
+public class CreeperSwellEvent extends EntityEvent implements Cancellable {
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+
+    private boolean cancelled;
+    private int swellChange;
+    private int finalSwellChange;
+    private final int currentSwell;
+    private final int maxSwell;
+    private final SwellReason swellReason;
+
+    @ApiStatus.Internal
+    public CreeperSwellEvent(final Creeper creeper, int swellChange, int finalSwellChange, int currentSwell,
+                             int maxSwell, SwellReason swellReason) {
+        super(creeper);
+        this.swellChange = swellChange;
+        this.finalSwellChange = finalSwellChange;
+        this.currentSwell = currentSwell;
+        this.maxSwell = maxSwell;
+        this.swellReason = swellReason;
+    }
+
+    /**
+     * Gets the cancellation state of this event. A cancelled event will not
+     * be executed in the server, but will still pass to other plugins
+     *
+     * @return {@code true} if this event is cancelled
+     */
+    @Override
+    public boolean isCancelled() {
+        return this.cancelled;
+    }
+
+    /**
+     * Sets the cancellation state of this event. A cancelled event will not
+     * be executed in the server, but will still pass to other plugins.
+     *
+     * @param cancel {@code true} if you wish to cancel this event
+     */
+    @Override
+    public void setCancelled(final boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    /**
+     * Returns the Entity involved in this event
+     *
+     * @return Entity who is involved in this event
+     */
+    @Override
+    public Creeper getEntity() {
+        return (Creeper) super.getEntity();
+    }
+
+    /**
+     * Gets the current swell level of the {@link Creeper}
+     *
+     * @return current swell level of the {@link Creeper}
+     */
+    public int getCurrentSwell() {
+        return this.currentSwell;
+    }
+
+    /**
+     * Gets the current maximum swell level of the {@link Creeper}
+     *
+     * @return maximum swell level of the {@link Creeper}
+     */
+    public int getMaxSwell() {
+        return this.maxSwell;
+    }
+
+    /**
+     * Gets the raw swell change before clamping
+     *
+     * @return the raw swell change
+     */
+    public int getSwellChange() {
+        return this.swellChange;
+    }
+
+    /**
+     * Gets the final swell change that will actually be applied to the {@link Creeper}
+     *
+     * @return the final swell change
+     */
+    public int getFinalSwellChange() {
+        return this.finalSwellChange;
+    }
+
+    /**
+     * Sets the swell change to apply to the {@link Creeper}
+     * <p>
+     * The swell change will be clamped to keep the {@link Creeper}'s swell level within [0, maxSwell]
+     *
+     * @param newSwellChange the swell change to apply
+     * @see #getFinalSwellChange()
+     */
+    public void setSwellChange(int newSwellChange) {
+        this.swellChange = newSwellChange;
+        // don't allow creeper swell level to go below 0 or above maxSwell
+        if (this.currentSwell + newSwellChange < 0) {
+            this.finalSwellChange = -this.currentSwell;
+        } else if (this.currentSwell + newSwellChange > this.maxSwell) {
+            this.finalSwellChange = this.maxSwell - this.currentSwell;
+        } else {
+            this.finalSwellChange = newSwellChange;
+        }
+    }
+
+    /**
+     * Gets the reason for the swell change
+     *
+     * @return a SwellReason value detailing the cause of the swell change
+     */
+    public SwellReason getSwellReason() {
+        return this.swellReason;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+
+    /**
+     * An enum to specify the reason for a creeper swell change
+     */
+    public enum SwellReason {
+        /**
+         * Swelling caused by the creeper being primed (by proximity or ignition)
+         */
+        PRIMED,
+        /**
+         * Swelling caused by the creeper falling from a height
+         */
+        FALL_DAMAGE,
+        /**
+         * Swelling caused by custom behavior, such as a plugin
+         */
+        CUSTOM
+    }
+}

paper-server/patches/sources/net/minecraft/world/entity/monster/Creeper.java.patch

@@ -8,6 +8,30 @@
 
      public Creeper(final EntityType<? extends Creeper> type, final Level level) {
          super(type, level);
+@@ -86,10 +_,20 @@
+     @Override
+     public boolean causeFallDamage(final double fallDistance, final float damageModifier, final DamageSource damageSource) {
+         boolean damaged = super.causeFallDamage(fallDistance, damageModifier, damageSource);
+-        this.swell += (int)(fallDistance * 1.5);
+-        if (this.swell > this.maxSwell - 5) {
+-            this.swell = this.maxSwell - 5;
++        // Paper start - CreeperSwellEvent; fire event for fall damage swell
++        int swellChange = (int)(fallDistance * 1.5);
++        int maxAllowedSwell = this.maxSwell - 5;
++        int finalSwellChange = Math.min(swellChange, maxAllowedSwell - this.swell);
++        if (finalSwellChange > 0) {
++            io.papermc.paper.event.entity.CreeperSwellEvent event = new io.papermc.paper.event.entity.CreeperSwellEvent(
++                (org.bukkit.entity.Creeper) this.getBukkitEntity(), swellChange, finalSwellChange, this.swell,
++                this.maxSwell, io.papermc.paper.event.entity.CreeperSwellEvent.SwellReason.FALL_DAMAGE);
++            event.callEvent();
++            if (!event.isCancelled()) {
++                this.swell += event.getFinalSwellChange();
++            }
+         }
++        // Paper end - CreeperSwellEvent
+
+         return damaged;
+     }
 @@ -118,7 +_,7 @@
          this.maxSwell = input.getShortOr("Fuse", (short)30);
          this.explosionRadius = input.getByteOr("ExplosionRadius", (byte)3);
@@ -17,6 +41,35 @@
          }
      }
 
+@@ -131,12 +_,23 @@
+             }
+
+             int swellDir = this.getSwellDir();
+-            if (swellDir > 0 && this.swell == 0) {
+-                this.playSound(SoundEvents.CREEPER_PRIMED, 1.0F, 0.5F);
+-                this.gameEvent(GameEvent.PRIME_FUSE);
++            // Paper start - CreeperSwellEvent; fire if swell will change this tick
++            if (swellDir != 0) {
++                int finalSwellChange = Math.clamp(swellDir, -this.swell, this.maxSwell - this.swell);
++                io.papermc.paper.event.entity.CreeperSwellEvent event = new io.papermc.paper.event.entity.CreeperSwellEvent(
++                    (org.bukkit.entity.Creeper) this.getBukkitEntity(), swellDir, finalSwellChange, this.swell, this.maxSwell,
++                    io.papermc.paper.event.entity.CreeperSwellEvent.SwellReason.PRIMED);
++                event.callEvent();
++                if (!event.isCancelled()) {
++                    int change = event.getFinalSwellChange();
++                    if (change > 0 && this.swell == 0) {
++                        this.playSound(SoundEvents.CREEPER_PRIMED, 1.0F, 0.5F);
++                        this.gameEvent(GameEvent.PRIME_FUSE);
++                    }
++                    this.swell += change;
++                }
+             }
+-
+-            this.swell += swellDir;
++            // Paper end - CreeperSwellEvent
+             if (this.swell < 0) {
+                 this.swell = 0;
+             }
 @@ -151,10 +_,11 @@
      }
 
@@ -63,7 +116,7 @@
                      itemStack.shrink(1);
                  } else {
                      itemStack.hurtAndBreak(1, player, hand.asEquipmentSlot());
-@@ -231,18 +_,29 @@
+@@ -231,18 +_,38 @@
      public void explodeCreeper() {
          if (this.level() instanceof ServerLevel level) {
              float explosionMultiplier = this.isPowered() ? 2.0F : 1.0F;
@@ -80,7 +133,16 @@
 +            this.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.EXPLODE); // CraftBukkit - add Bukkit remove cause
 +            // CraftBukkit start
 +            } else {
-+                this.swell = 0;
++                // Paper start - CreeperSwellEvent; reset swell through event when explosion is cancelled
++                io.papermc.paper.event.entity.CreeperSwellEvent swellEvent =
++                    new io.papermc.paper.event.entity.CreeperSwellEvent((org.bukkit.entity.Creeper) getBukkitEntity(),
++                        -this.swell, -this.swell, this.swell, this.maxSwell,
++                        io.papermc.paper.event.entity.CreeperSwellEvent.SwellReason.CUSTOM);
++                swellEvent.callEvent();
++                if (!swellEvent.isCancelled()) {
++                    this.swell += swellEvent.getFinalSwellChange();
++                }
++                // Paper end - CreeperSwellEvent
 +                this.entityData.set(DATA_IS_IGNITED, false); // Paper
 +            }
 +            // CraftBukkit end