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 1274b40a424371b77d8df70ea5f4b2b7300e2a83..864ab97b7a6c62c376ca38dbbc65bc9406dfd62b 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -265,6 +265,7 @@ public abstract class LivingEntity extends Entity {
     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() {
@@ -705,7 +706,7 @@ public abstract class LivingEntity extends Entity {
     }
 
     public boolean shouldDiscardFriction() {
-        return this.discardFriction;
+        return !this.frictionState.toBooleanOrElse(!this.discardFriction); // Paper
     }
 
     public void setDiscardFriction(boolean noDrag) {
@@ -750,6 +751,11 @@ public abstract class LivingEntity extends Entity {
 
     @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);
@@ -792,6 +798,15 @@ public abstract class LivingEntity extends Entity {
             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 b0976c20c0b7ff0637809ed2082771f5b6f10b7a..f0ccdfbd7d7be8c6e302609accf8fe9cac8885c4 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -53,6 +53,7 @@ public class ItemEntity extends Entity {
     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);
@@ -150,7 +151,11 @@ public class ItemEntity extends Entity {
                 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(new BlockPos(this.getX(), this.getY() - 1.0D, this.getZ())).getBlock().getFriction() * 0.98F;
                 }
 
@@ -351,6 +356,11 @@ public class ItemEntity extends Entity {
 
     @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);
@@ -384,6 +394,17 @@ public class ItemEntity extends Entity {
             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 fea44ba6a6584b4a510af6a58cab07eecec6b68b..ecec5e17807a760769fc0ea79c2a0161cc5db1ef 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 fe9f52176d87944ac5743dced8cf4d0576089d06..09da9d3c85e36c2a78663f58a97963dbc795a367 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
@@ -1036,6 +1036,18 @@ 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");
