From 0a1bf06c6f3c9f40fcb65d771a5d81ab268c5cef Mon Sep 17 00:00:00 2001
From: theophriene <60849082+theophriene@users.noreply.github.com>
Date: Mon, 21 Sep 2020 14:41:31 +0000
Subject: Trapdoor crash fix (#4890)

* [WIP] Trapdoor crash fix

* Fixed code style

* Updated commentary in the code

* Updated commentary in the code again

* Fix copy-past error

* Fix another copy-past error!

* Fixed orientation & clipping

* Remove redundant clause

* Some code cleanup

* Fixed compilation error

* Moved logic into helper function, slightly reorganised the caller

* Fixed comments

* Fixed comments, what an idiot

* Added to CONTRIBUTORS

* Fixed bitwise error

* Use cYawRotator

* Reduce indent

Co-authored-by: Elias Thomson <fiv.pids@gmail.com>
Co-authored-by: Tiger Wang <ziwei.tiger@outlook.com>
---
 CONTRIBUTORS               |  1 +
 src/Blocks/BlockTrapdoor.h | 34 ++++++++++++++++++++++++++++------
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 4841ad203..cf9841ff4 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -65,6 +65,7 @@ sweetgiorni
 Sxw1212
 Taugeshtu
 tigerw (Tiger Wang)
+theophriene
 tonibm19
 TooAngel
 UltraCoderRU
diff --git a/src/Blocks/BlockTrapdoor.h b/src/Blocks/BlockTrapdoor.h
index dce246dea..2392fc2d3 100644
--- a/src/Blocks/BlockTrapdoor.h
+++ b/src/Blocks/BlockTrapdoor.h
@@ -9,9 +9,9 @@
 
 
 class cBlockTrapdoorHandler :
-	public cClearMetaOnDrop<cMetaRotator<cBlockHandler, 0x03, 0x01, 0x02, 0x00, 0x03, false>>
+	public cClearMetaOnDrop<cYawRotator<cBlockHandler, 0x03, 0x01, 0x02, 0x00, 0x03, false>>
 {
-	using Super = cClearMetaOnDrop<cMetaRotator<cBlockHandler, 0x03, 0x01, 0x02, 0x00, 0x03, false>>;
+	using Super = cClearMetaOnDrop<cYawRotator<cBlockHandler, 0x03, 0x01, 0x02, 0x00, 0x03, false>>;
 
 public:
 
@@ -80,13 +80,38 @@ private:
 		BLOCKTYPE & a_BlockType, NIBBLETYPE & a_BlockMeta
 	) const override
 	{
+		if (a_ClickedBlockFace == BLOCK_FACE_YP)
+		{
+			// Trapdoor is placed on top of a block.
+			// Engage yaw rotation to determine hinge direction:
+			return Super::GetPlacementBlockTypeMeta(a_ChunkInterface, a_Player, a_PlacedBlockPos, a_ClickedBlockFace, a_CursorPos, a_BlockType, a_BlockMeta);
+		}
+		else if (a_ClickedBlockFace == BLOCK_FACE_YM)
+		{
+			// Trapdoor is placed on bottom of a block.
+			// Engage yaw rotation to determine hinge direction:
+			if (!Super::GetPlacementBlockTypeMeta(a_ChunkInterface, a_Player, a_PlacedBlockPos, a_ClickedBlockFace, a_CursorPos, a_BlockType, a_BlockMeta))
+			{
+				return false;
+			}
+
+			// Toggle 'Move up half-block' bit on:
+			a_BlockMeta |= 0x8;
+
+			return true;
+		}
+
+		// Placement on block sides; hinge direction is determined by which side was clicked:
 		a_BlockType = m_BlockType;
 		a_BlockMeta = BlockFaceToMetaData(a_ClickedBlockFace);
 
 		if (a_CursorPos.y > 7)
 		{
+			// Trapdoor is placed on a higher half of a vertical block.
+			// Toggle 'Move up half-block' bit on:
 			a_BlockMeta |= 0x8;
 		}
+
 		return true;
 	}
 
@@ -102,15 +127,12 @@ private:
 			case BLOCK_FACE_ZM: return 0x0;
 			case BLOCK_FACE_XP: return 0x3;
 			case BLOCK_FACE_XM: return 0x2;
-			case BLOCK_FACE_NONE:
-			case BLOCK_FACE_YM:
-			case BLOCK_FACE_YP:
+			default:
 			{
 				ASSERT(!"Unhandled block face!");
 				return 0;
 			}
 		}
-		UNREACHABLE("Unsupported block face");
 	}
 
 
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