Paper/patches/server/0902-Friction-API.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Noah van der Aa <ndvdaa@gmail.com>
Date: Wed, 15 Sep 2021 20:44:22 +0200
Subject: [PATCH] Friction API


diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 3b480415f6c862206dd733c6a3ffda451668d24b..fb3eb0125e524c5a06b21c5a6e80f5b6220460cd 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -262,6 +262,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
     public boolean bukkitPickUpLoot;
     public org.bukkit.craftbukkit.entity.CraftLivingEntity getBukkitLivingEntity() { return (org.bukkit.craftbukkit.entity.CraftLivingEntity) super.getBukkitEntity(); } // Paper
     public boolean silentDeath = false; // Paper - mark entity as dying silently for cancellable death event
+    public net.kyori.adventure.util.TriState frictionState = net.kyori.adventure.util.TriState.NOT_SET; // Paper
 
     @Override
     public float getBukkitYaw() {
@@ -717,7 +718,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
     }
 
     public boolean shouldDiscardFriction() {
-        return this.discardFriction;
+        return !this.frictionState.toBooleanOrElse(!this.discardFriction); // Paper
     }
 
     public void setDiscardFriction(boolean noDrag) {
@@ -761,6 +762,11 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
     @Override
     public void addAdditionalSaveData(CompoundTag nbt) {
+        // Paper start
+        if (this.frictionState != net.kyori.adventure.util.TriState.NOT_SET) {
+            nbt.putString("Paper.FrictionState", this.frictionState.toString());
+        }
+        // Paper end
         nbt.putFloat("Health", this.getHealth());
         nbt.putShort("HurtTime", (short) this.hurtTime);
         nbt.putInt("HurtByTimestamp", this.lastHurtByMobTimestamp);
@@ -803,6 +809,15 @@ public abstract class LivingEntity extends Entity implements Attackable {
             absorptionAmount = 0;
         }
         this.setAbsorptionAmount(absorptionAmount);
+
+        if (nbt.contains("Paper.FrictionState")) {
+            String fs = nbt.getString("Paper.FrictionState");
+            try {
+                frictionState = net.kyori.adventure.util.TriState.valueOf(fs);
+            } catch (Exception ignored) {
+                LOGGER.error("Unknown friction state " + fs + " for " + this);
+            }
+        }
         // Paper end
         if (nbt.contains("Attributes", 9) && this.level() != null && !this.level().isClientSide) {
             this.getAttributes().load(nbt.getList("Attributes", 10));
diff --git a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
index 08a2ce0ab024b99df5f6e23aa5a13c9d6f431db6..52196431a6538872755344859a0454a0e50c3b6e 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -55,6 +55,7 @@ public class ItemEntity extends Entity implements TraceableEntity {
     private int lastTick = MinecraftServer.currentTick - 1; // CraftBukkit
     public boolean canMobPickup = true; // Paper
     private int despawnRate = -1; // Paper
+    public net.kyori.adventure.util.TriState frictionState = net.kyori.adventure.util.TriState.NOT_SET; // Paper
 
     public ItemEntity(EntityType<? extends ItemEntity> type, Level world) {
         super(type, world);
@@ -160,7 +161,11 @@ public class ItemEntity extends Entity implements TraceableEntity {
                 this.move(MoverType.SELF, this.getDeltaMovement());
                 float f1 = 0.98F;
 
-                if (this.onGround()) {
+                // Paper start
+                if (frictionState == net.kyori.adventure.util.TriState.FALSE) {
+                    f1 = 1F;
+                } else if (this.onGround()) {
+                    // Paper end
                     f1 = this.level().getBlockState(this.getBlockPosBelowThatAffectsMyMovement()).getBlock().getFriction() * 0.98F;
                 }
 
@@ -369,6 +374,11 @@ public class ItemEntity extends Entity implements TraceableEntity {
 
     @Override
     public void addAdditionalSaveData(CompoundTag nbt) {
+        // Paper start
+        if (this.frictionState != net.kyori.adventure.util.TriState.NOT_SET) {
+            nbt.putString("Paper.FrictionState", this.frictionState.toString());
+        }
+        // Paper end
         nbt.putShort("Health", (short) this.health);
         nbt.putShort("Age", (short) this.age);
         nbt.putShort("PickupDelay", (short) this.pickupDelay);
@@ -402,6 +412,17 @@ public class ItemEntity extends Entity implements TraceableEntity {
             this.thrower = nbt.getUUID("Thrower");
         }
 
+        // Paper start
+        if (nbt.contains("Paper.FrictionState")) {
+            String fs = nbt.getString("Paper.FrictionState");
+            try {
+                frictionState = net.kyori.adventure.util.TriState.valueOf(fs);
+            } catch (Exception ignored) {
+                com.mojang.logging.LogUtils.getLogger().error("Unknown friction state " + fs + " for " + this);
+            }
+        }
+        // Paper end
+
         CompoundTag nbttagcompound1 = nbt.getCompound("Item");
 
         this.setItem(ItemStack.of(nbttagcompound1));
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
index e9946edf568db010e4ccb9fe7755709ed7b8310f..a925b5c490e7129b27370aa57b5fad1cf05530c6 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftItem.java
@@ -103,6 +103,18 @@ public class CraftItem extends CraftEntity implements Item {
         item.age = willAge ? 0 : NO_AGE_TIME;
      }
 
+     @org.jetbrains.annotations.NotNull
+     @Override
+     public net.kyori.adventure.util.TriState getFrictionState() {
+        return this.item.frictionState;
+     }
+
+     @Override
+     public void setFrictionState(@org.jetbrains.annotations.NotNull net.kyori.adventure.util.TriState state) {
+         java.util.Objects.requireNonNull(state, "state may not be null");
+         this.item.frictionState = state;
+     }
+
     @Override
     public int getHealth() {
         return item.health;
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
index 83429bfd26128e85864806699017a481109e75e4..b166ca8b8d21b3f7e930fa9b9b71fbca70bfdb97 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
@@ -1064,6 +1064,18 @@ public class CraftLivingEntity extends CraftEntity implements LivingEntity {
         });
     }
 
+    @org.jetbrains.annotations.NotNull
+    @Override
+    public net.kyori.adventure.util.TriState getFrictionState() {
+        return this.getHandle().frictionState;
+    }
+
+    @Override
+    public void setFrictionState(@org.jetbrains.annotations.NotNull net.kyori.adventure.util.TriState state) {
+        java.util.Objects.requireNonNull(state, "state may not be null");
+        this.getHandle().frictionState = state;
+    }
+
     @Override
     public void knockback(double strength, double directionX, double directionZ) {
         Preconditions.checkArgument(strength > 0, "Knockback strength must be > 0");