Implement farmland trampling (#5401)

* Add DarkoGNU to CONTRIBUTORS

* HandleFarmlandTrampling function & its docs

* Fix decimal separators (, -> .)

* Fix style. Adjust thresholds. Make function non-virtual

* Adjust thresholds again. Prepare for fixing #5402

* Trying to fix falling through farmlands

* Another style fix

* Add FarmlandTramplingEnabled to world.ini

* Docs for IsFarmlandTramplingEnabled

* Style

* Farmland trampling - handling the random chance

* Trampling kinda works, very buggy

* Trying to fix clang-tidy

* Fix trampling

* Trying to fix the 'undocumented API symbol'

* Implement bearbin's suggestions

* Calculate volume properly

* Don't use std::pow for squaring

* Improved comments

* Really, should comments' style be checked?

CONTRIBUTORS

@@ -17,6 +17,7 @@ birkett (Anthony Birkett)
 Bond_009
 changyongGuo
 Cocosushi6
+DarkoGNU
 derouinw
 dImrich (Damian Imrich)
 Diusrex

Server/Plugins/APIDump/Classes/World.lua

@@ -2245,6 +2245,16 @@ function OnAllChunksAvailable()</pre> All return values from the callbacks are i
 				},
 				Notes = "Returns whether the configuration has DeepSnow enabled.",
 			},
+			IsFarmlandTramplingEnabled =
+			{
+				Returns =
+				{
+					{
+						Type = "boolean",
+					},
+				},
+				Notes = "Returns true if farmland trampling is enabled.",
+			},
 			IsGameModeAdventure =
 			{
 				Returns =

src/BlockInfo.cpp

@@ -1164,6 +1164,7 @@ float cBlockInfo::GetBlockHeight(const BLOCKTYPE Block)
 		case E_BLOCK_DARK_OAK_FENCE:      return 1.5;
 		case E_BLOCK_DARK_OAK_FENCE_GATE: return 1.5;
 		case E_BLOCK_ENCHANTMENT_TABLE:   return 0.75;    // 12 pixels
+		case E_BLOCK_FARMLAND:            return 0.9375;  // 15 pixels
 		case E_BLOCK_FENCE:               return 1.5;
 		case E_BLOCK_JUNGLE_FENCE:        return 1.5;
 		case E_BLOCK_JUNGLE_FENCE_GATE:   return 1.5;

src/Blocks/BlockFarmland.h

@@ -10,7 +10,10 @@
 #pragma once
 
 #include "BlockHandler.h"
+#include "ChunkInterface.h"
 #include "../BlockArea.h"
+#include "../Chunk.h"
+#include "../ClientHandle.h"
 
 
 
@@ -25,6 +28,58 @@ public:
 
 	using Super::Super;
 
+	/** Turns farmland into dirt.
+	Will first check for any colliding entities and teleport them to a higher position.
+	*/
+	static void TurnToDirt(cChunk & a_Chunk, Vector3i a_AbsPos)
+	{
+		auto RelPos = cChunkDef::AbsoluteToRelative(a_AbsPos);
+		TurnToDirt(a_Chunk, a_AbsPos, RelPos);
+	}
+
+
+
+
+
+	/** Turns farmland into dirt.
+	Will first check for any colliding entities and teleport them to a higher position.
+	*/
+	static void TurnToDirt(cChunk & a_Chunk, Vector3i a_AbsPos, Vector3i a_RelPos)
+	{
+		static const auto FarmlandHeight = cBlockInfo::GetBlockHeight(E_BLOCK_FARMLAND);
+		static const auto FullHeightDelta = 1 - FarmlandHeight;
+
+		a_Chunk.ForEachEntityInBox(
+			cBoundingBox(Vector3d(0.5, FarmlandHeight, 0.5) + a_AbsPos, 0.5, FullHeightDelta),
+			[&](cEntity & Entity)
+			{
+				if (!Entity.IsOnGround())
+				{
+					return false;
+				}
+				Entity.AddPosY(FullHeightDelta);
+
+				// Players need a packet that will update their position
+				if (Entity.IsPlayer())
+				{
+					auto Player = static_cast<cPlayer *>(&Entity);
+					// This works, but it's much worse than Vanilla.
+					// This can be easily improved by implementing relative
+					// "Player Position And Look" packets! See
+					// https://wiki.vg/Protocol#Player_Position_And_Look_.28clientbound.29
+					Player->GetClientHandle()->SendPlayerMoveLook();
+				}
+
+				return false;
+			});
+
+		a_Chunk.SetBlock(a_RelPos, E_BLOCK_DIRT, 0);
+	}
+
+
+
+
+
 private:
 
 	virtual cItems ConvertToPickups(const NIBBLETYPE a_BlockMeta, const cItem * const a_Tool) const override
@@ -76,7 +131,8 @@ private:
 			}
 			default:
 			{
-				a_Chunk.SetBlock(a_RelPos, E_BLOCK_DIRT, 0);
+				auto AbsPos = a_Chunk.RelativeToAbsolute(a_RelPos);
+				TurnToDirt(a_Chunk, AbsPos, a_RelPos);
 				break;
 			}
 		}
@@ -101,10 +157,17 @@ private:
 		}
 
 		// Check whether we should revert to dirt:
+		// TODO: fix for signs and slabs (possibly more blocks) - they should destroy farmland
 		auto upperBlock = a_ChunkInterface.GetBlock(a_BlockPos.addedY(1));
 		if (cBlockInfo::FullyOccupiesVoxel(upperBlock))
 		{
-			a_ChunkInterface.SetBlock(a_BlockPos, E_BLOCK_DIRT, 0);
+			// Until the fix above is done, this line should also suffice:
+			// a_ChunkInterface.SetBlock(a_BlockPos, E_BLOCK_DIRT, 0);
+			a_ChunkInterface.DoWithChunkAt(a_BlockPos, [&](cChunk & Chunk)
+			{
+				TurnToDirt(Chunk, a_BlockPos);
+				return true;
+			});
 		}
 	}
 

src/Entities/Pawn.cpp

@@ -8,6 +8,7 @@
 #include "../Bindings/PluginManager.h"
 #include "../BoundingBox.h"
 #include "../Blocks/BlockHandler.h"
+#include "../Blocks/BlockFarmland.h"
 #include "../EffectID.h"
 #include "../Mobs/Monster.h"
 
@@ -430,7 +431,9 @@ void cPawn::HandleFalling(void)
 
 	if (OnGround)
 	{
-		auto Damage = static_cast<int>(m_LastGroundHeight - GetPosY() - 3.0);
+		auto FallHeight = m_LastGroundHeight - GetPosY();
+		auto Damage = static_cast<int>(FallHeight - 3.0);
+
 		if ((Damage > 0) && !FallDamageAbsorbed)
 		{
 			if (IsElytraFlying())
@@ -438,7 +441,6 @@ void cPawn::HandleFalling(void)
 				Damage = static_cast<int>(static_cast<float>(Damage) * 0.33);
 			}
 
-			// Fall particles:
 			if (const auto Below = POS_TOINT.addedY(-1); Below.y >= 0)
 			{
 				const auto BlockBelow = GetWorld()->GetBlock(Below);
@@ -448,6 +450,7 @@ void cPawn::HandleFalling(void)
 					Damage = std::clamp(static_cast<int>(static_cast<float>(Damage) * 0.2), 1, 20);
 				}
 
+				// Fall particles
 				GetWorld()->BroadcastParticleEffect(
 					"blockdust",
 					GetPosition(),
@@ -463,6 +466,15 @@ void cPawn::HandleFalling(void)
 
 		m_bTouchGround = true;
 		m_LastGroundHeight = GetPosY();
+
+		// Farmland trampling. Mobs smaller than 0.512 cubic blocks won't trample (Java Edition's behavior)
+		// We only have width and height, so we have to calculate Width^2
+		if (GetWorld()->IsFarmlandTramplingEnabled() &&
+			(BlockAtFoot == E_BLOCK_FARMLAND) &&
+			(GetWidth() * GetWidth() * GetHeight() >= 0.512))
+		{
+			HandleFarmlandTrampling(FallHeight);
+		}
 	}
 	else
 	{
@@ -478,6 +490,42 @@ void cPawn::HandleFalling(void)
 
 
 
+void cPawn::HandleFarmlandTrampling(double a_FallHeight)
+{
+	bool ShouldTrample = true;
+	auto & Random = GetRandomProvider();
+
+	// No trampling if FallHeight <= 0.6875
+	if (a_FallHeight <= 0.6875)
+	{
+		ShouldTrample = false;
+	}
+	// For FallHeight <= 1.5625 we need to get a random bool
+	else if (a_FallHeight <= 1.0625)
+	{
+		ShouldTrample = Random.RandBool(0.25);
+	}
+	else if (a_FallHeight <= 1.5625)
+	{
+		ShouldTrample = Random.RandBool(0.66);
+	}
+	// For FallHeight > 1.5625 we always trample - ShouldTrample remains true
+
+	if (ShouldTrample)
+	{
+		auto AbsPos = GetPosition().Floor();
+		GetWorld()->DoWithChunkAt(AbsPos, [&](cChunk & Chunk)
+		{
+			cBlockFarmlandHandler::TurnToDirt(Chunk, AbsPos);
+			return true;
+		});
+	}
+}
+
+
+
+
+
 void cPawn::OnRemoveFromWorld(cWorld & a_World)
 {
 	StopEveryoneFromTargetingMe();

src/Entities/Pawn.h

@@ -33,6 +33,16 @@ public:
 	virtual void HandleFalling(void);
 	virtual void OnRemoveFromWorld(cWorld & a_World) override;
 
+	/** Handles farmland trampling when hitting the ground.
+	Algorithm:
+	fall height <= 0.6875 blocks: no trampling
+	fall height > 0.6875 and <= 1.0625: 25% chance of trampling
+	fall height > 1.0625 and <= 1.5625: 66% chance of trampling
+	fall height > 1.5625: always trample
+	The values may differ from vanilla, they were determined experimentally.
+	*/
+	void HandleFarmlandTrampling(double a_FallHeight);
+
 	/** Tells all pawns which are targeting us to stop targeting us. */
 	void StopEveryoneFromTargetingMe();
 

src/World.cpp

@@ -166,6 +166,7 @@ cWorld::cWorld(
 	m_SkyDarkness(0),
 	m_GameMode(gmSurvival),
 	m_bEnabledPVP(false),
+	m_bFarmlandTramplingEnabled(false),
 	m_IsDeepSnowEnabled(false),
 	m_ShouldLavaSpawnFire(true),
 	m_VillagersShouldHarvestCrops(true),
@@ -300,6 +301,7 @@ cWorld::cWorld(
 	int TNTShrapnelLevel          = IniFile.GetValueSetI("Physics",       "TNTShrapnelLevel",            static_cast<int>(slAll));
 	m_bCommandBlocksEnabled       = IniFile.GetValueSetB("Mechanics",     "CommandBlocksEnabled",        false);
 	m_bEnabledPVP                 = IniFile.GetValueSetB("Mechanics",     "PVPEnabled",                  true);
+	m_bFarmlandTramplingEnabled   = IniFile.GetValueSetB("Mechanics",     "FarmlandTramplingEnabled",    true);
 	m_bUseChatPrefixes            = IniFile.GetValueSetB("Mechanics",     "UseChatPrefixes",             true);
 	m_MinNetherPortalWidth        = IniFile.GetValueSetI("Mechanics",     "MinNetherPortalWidth",        2);
 	m_MaxNetherPortalWidth        = IniFile.GetValueSetI("Mechanics",     "MaxNetherPortalWidth",        21);

src/World.h

@@ -121,6 +121,9 @@ public:
 
 	bool IsPVPEnabled(void) const { return m_bEnabledPVP; }
 
+	/** Returns true if farmland trampling is enabled */
+	bool IsFarmlandTramplingEnabled(void) const { return m_bFarmlandTramplingEnabled; }
+
 	bool IsDeepSnowEnabled(void) const { return m_IsDeepSnowEnabled; }
 
 	bool ShouldLavaSpawnFire(void) const { return m_ShouldLavaSpawnFire; }
@@ -997,6 +1000,7 @@ private:
 
 	eGameMode m_GameMode;
 	bool m_bEnabledPVP;
+	bool m_bFarmlandTramplingEnabled;
 	bool m_IsDeepSnowEnabled;
 	bool m_ShouldLavaSpawnFire;
 	bool m_VillagersShouldHarvestCrops;