Add a event for modify player's movement during using item

fabric-entity-events-v1/src/client/java/net/fabricmc/fabric/api/entity/event/client/ClientPlayerEvents.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.entity.event.client;
+
+import org.jetbrains.annotations.Nullable;
+
+import net.minecraft.client.network.ClientPlayerEntity;
+
+import net.fabricmc.fabric.api.event.Event;
+import net.fabricmc.fabric.api.event.EventFactory;
+
+public final class ClientPlayerEvents {
+	/**
+	 * An event that is called when a player is moving while using an item.
+	 */
+	public static final Event<ModifyItemUseMovementSpeed> MODIFY_ITEM_USE_MOVEMENT_SPEED = EventFactory.createArrayBacked(ModifyItemUseMovementSpeed.class, callbacks -> player -> {
+		Float maxSpeedPercentage = null;
+
+		for (ModifyItemUseMovementSpeed callback : callbacks) {
+			Float speedPercentage = callback.modifyItemUseMovementSpeed(player);
+
+			if (speedPercentage != null) {
+				maxSpeedPercentage = maxSpeedPercentage == null ? speedPercentage : Math.max(speedPercentage, maxSpeedPercentage);
+			}
+		}
+
+		return maxSpeedPercentage;
+	});
+
+	@FunctionalInterface
+	public interface ModifyItemUseMovementSpeed {
+		/**
+		 * Called when a player is moving while using an item.
+		 *
+		 * @param player the player that is moving while using an item.
+		 * @return a Float representing the speed modification as a percentage (e.g., 0.8 for 80% speed),
+		 * or {@code null} indicates that no modification should be applied.
+		 */
+		@Nullable
+		Float modifyItemUseMovementSpeed(ClientPlayerEntity player);
+	}
+}

fabric-entity-events-v1/src/client/java/net/fabricmc/fabric/mixin/client/entity/event/ClientPlayerMixin.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.mixin.client.entity.event;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import net.minecraft.client.network.ClientPlayerEntity;
+
+import net.fabricmc.fabric.api.entity.event.client.ClientPlayerEvents;
+
+@Mixin(ClientPlayerEntity.class)
+abstract class ClientPlayerMixin {
+	@Inject(method = "tickMovement", at = @At(value = "INVOKE", target = "Lnet/minecraft/client/network/ClientPlayerEntity;isUsingItem()Z"))
+	private void invokeModifyItemUseMovementSpeedEvent(CallbackInfo ci) {
+		ClientPlayerEntity player = (ClientPlayerEntity) (Object) this;
+
+		if (player.isUsingItem() && !player.hasVehicle() && (player.input.movementForward != 0.0F || player.input.movementSideways != 0.0F)) {
+			Float speedPercentage = ClientPlayerEvents.MODIFY_ITEM_USE_MOVEMENT_SPEED.invoker().modifyItemUseMovementSpeed(player);
+
+			if (speedPercentage != null) {
+				player.input.movementSideways *= speedPercentage * 5.0F;
+				player.input.movementForward *= speedPercentage * 5.0F;
+			}
+		}
+	}
+}

fabric-entity-events-v1/src/client/resources/fabric-entity-events-v1.client.mixins.json

@@ -3,7 +3,8 @@
   "package": "net.fabricmc.fabric.mixin.client.entity.event",
   "compatibilityLevel": "JAVA_17",
   "client": [
-    "elytra.ClientPlayerEntityMixin"
+    "elytra.ClientPlayerEntityMixin",
+    "ClientPlayerMixin"
   ],
   "injectors": {
     "defaultRequire": 1,

fabric-entity-events-v1/src/testmodClient/java/net/fabricmc/fabric/test/entity/event/client/EntityEventTestsClient.java

@@ -16,17 +16,64 @@
 
 package net.fabricmc.fabric.test.entity.event.client;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import net.minecraft.entity.EquipmentSlot;
+import net.minecraft.item.Items;
 
 import net.fabricmc.api.ClientModInitializer;
 import net.fabricmc.fabric.api.client.rendering.v1.LivingEntityFeatureRenderEvents;
+import net.fabricmc.fabric.api.entity.event.client.ClientPlayerEvents;
 import net.fabricmc.fabric.test.entity.event.EntityEventTests;
 
 public class EntityEventTestsClient implements ClientModInitializer {
+	private static final Logger LOGGER = LoggerFactory.getLogger(EntityEventTestsClient.class);
+
 	@Override
 	public void onInitializeClient() {
 		LivingEntityFeatureRenderEvents.ALLOW_CAPE_RENDER.register(player -> {
 			return !player.getEquippedStack(EquipmentSlot.CHEST).isOf(EntityEventTests.DIAMOND_ELYTRA);
 		});
+
+		// the most common usage is to modify using item speed based on main hand item, most for custom items.
+		ClientPlayerEvents.MODIFY_ITEM_USE_MOVEMENT_SPEED.register(player -> {
+			if (player.getMainHandStack().isOf(Items.GOLDEN_APPLE)) {
+				LOGGER.info("Player {} can move with half speed when eating golden apple.", player);
+				return 0.5F;
+			}
+
+			if (player.getMainHandStack().isOf(Items.ENCHANTED_GOLDEN_APPLE)) {
+				LOGGER.info("Player {} can move with normal speed when eating enchanted golden apple.", player);
+				return 1.0F;
+			}
+
+			return null;
+		});
+
+		// another possible usages is to modify using item speed when certain conditions (e.g. equipped items) are met.
+		ClientPlayerEvents.MODIFY_ITEM_USE_MOVEMENT_SPEED.register(player -> {
+			if (player.getMainHandStack().isOf(Items.BOW) && player.getEquippedStack(EquipmentSlot.FEET).isOf(Items.LEATHER_BOOTS)) {
+				LOGGER.info("Player {} can move with 80% speed becase of leather boots on feet.", player);
+				return 0.8F;
+			}
+
+			if (player.getMainHandStack().isOf(Items.BOW) && player.getEquippedStack(EquipmentSlot.FEET).isOf(Items.IRON_BOOTS)) {
+				LOGGER.info("Player {} can't move during using bow becase of iron boots on feet.", player);
+				return 0.0F;
+			}
+
+			return null;
+		});
+
+		// this is used to test when multiple mods modify the using item speed together.
+		ClientPlayerEvents.MODIFY_ITEM_USE_MOVEMENT_SPEED.register(player -> {
+			if (player.getMainHandStack().isOf(Items.BOW) && player.getOffHandStack().isOf(Items.FEATHER)) {
+				LOGGER.info("Player {} can move with half speed becase of feather in offhand.", player);
+				return 0.5F;
+			}
+
+			return null;
+		});
 	}
 }