Add PlayerTransientModifierUpdateEvent

paper-api/src/main/java/io/papermc/paper/event/player/PlayerTransientModifierUpdateEvent.java

@@ -0,0 +1,86 @@
+package io.papermc.paper.event.player;
+
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeModifier;
+import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.player.PlayerEvent;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Called when the server temporarily updates a player's modifier. This is not called for any arbitrary modifier update
+ * on the player.
+ * <p>
+ * Note: Currently only called when a player crouches making their waypoint transmit range attribute disappear.
+ * </p>
+ */
+@NullMarked
+public class PlayerTransientModifierUpdateEvent extends PlayerEvent implements Cancellable {
+
+    private static final  HandlerList HANDLER_LIST = new HandlerList();
+
+    private boolean cancelled;
+    private final boolean removal;
+    private final Attribute attribute;
+    private AttributeModifier modifier;
+
+    @ApiStatus.Internal
+    public PlayerTransientModifierUpdateEvent(Player player, boolean removal, Attribute attribute, AttributeModifier modifier) {
+        super(player);
+        this.removal = removal;
+        this.attribute = attribute;
+        this.modifier = modifier;
+    }
+
+    /**
+     * Returns whether this event involves a removal or addition of the transient modifier.
+     * @return whether the modifier is being removed
+     */
+    public boolean isRemoval() {
+        return this.removal;
+    }
+    /**
+     * The attribute type this modifier is being applied on.
+     * @return the attribute type
+     */
+    public Attribute getAttribute() {
+        return this.attribute;
+    }
+
+    /**
+     * Returns transient modifier to be updated.
+     * @return the modifier
+     */
+    public AttributeModifier getModifier() {
+        return this.modifier;
+    }
+
+    /**
+     * Sets the transient modifier to be updated.
+     * @param modifier the new modifier
+     */
+    public void setModifier(AttributeModifier modifier) {
+        this.modifier = modifier;
+    }
+
+    @Override
+    public void setCancelled(final boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return this.cancelled;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+}

paper-server/patches/sources/net/minecraft/server/level/ServerPlayer.java.patch

@@ -252,7 +252,22 @@
              this.containerMenu = this.inventoryMenu;
          }
 
-@@ -636,10 +_,10 @@
+@@ -626,20 +_,23 @@
+
+         AttributeInstance attribute2 = this.getAttribute(Attributes.WAYPOINT_TRANSMIT_RANGE);
+         if (attribute2 != null) {
++            io.papermc.paper.event.player.PlayerTransientModifierUpdateEvent event = new io.papermc.paper.event.player.PlayerTransientModifierUpdateEvent(this.getBukkitEntity(), this.isCrouching(), org.bukkit.attribute.Attribute.WAYPOINT_TRANSMIT_RANGE, org.bukkit.craftbukkit.attribute.CraftAttributeInstance.convert(WAYPOINT_TRANSMIT_RANGE_CROUCH_MODIFIER));
++            if (!event.callEvent()) return;
++            net.minecraft.world.entity.ai.attributes.AttributeModifier modifier = org.bukkit.craftbukkit.attribute.CraftAttributeInstance.convert(event.getModifier());
+             if (this.isCrouching()) {
+-                attribute2.addOrUpdateTransientModifier(WAYPOINT_TRANSMIT_RANGE_CROUCH_MODIFIER);
++                attribute2.addOrUpdateTransientModifier(modifier);
+             } else {
+-                attribute2.removeModifier(WAYPOINT_TRANSMIT_RANGE_CROUCH_MODIFIER);
++                attribute2.removeModifier(modifier);
+             }
+         }
+     }
 
      public void doTick() {
          try {