From fbd31c1bf8d692f493e7f4cf0decb6990c4cff34 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Thu, 3 Aug 2023 13:42:01 -0700
Subject: [PATCH] Fix display entities being upside down on 1.20.x

This was due to Mojang flipping them 180 on the y-axis in the 1.20 update
---
 gradle/wrapper/gradle-wrapper.properties      |  2 +-
 .../xyz/jpenilla/chesscraft/PieceHandler.java | 52 +++++++++++++++----
 2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 62f495d..9f4197d 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.2.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/src/main/java/xyz/jpenilla/chesscraft/PieceHandler.java b/src/main/java/xyz/jpenilla/chesscraft/PieceHandler.java
index 926e492..a22bd1b 100644
--- a/src/main/java/xyz/jpenilla/chesscraft/PieceHandler.java
+++ b/src/main/java/xyz/jpenilla/chesscraft/PieceHandler.java
@@ -40,6 +40,7 @@
 import org.bukkit.profile.PlayerTextures;
 import org.bukkit.util.Transformation;
 import org.joml.AxisAngle4f;
+import org.joml.Quaternionf;
 import org.joml.Vector3f;
 import xyz.jpenilla.chesscraft.config.PieceOptions;
 import xyz.jpenilla.chesscraft.data.CardinalDirection;
@@ -70,16 +71,7 @@ public void applyToWorld(final ChessBoard board, final BoardStateHolder game, fi
           return;
         }
         world.spawn(pos.toLocation(world), ItemDisplay.class, itemDisplay -> {
-          itemDisplay.setTransformation(new Transformation(
-            // center
-            new Vector3f(0.5f * board.scale(), 0, 0.5f * board.scale()),
-            // flip upwards
-            new AxisAngle4f((float) Math.toRadians(90.0D), 1, 0, 0),
-            // scale
-            new Vector3f(0.5f * board.scale()),
-            // rotate
-            new AxisAngle4f((float) Math.toRadians(rotation(board.facing(), piece)), 0, 0, 1)
-          ));
+          itemDisplay.setTransformation(transformationFor(board, piece));
           itemDisplay.setItemDisplayTransform(ItemDisplay.ItemDisplayTransform.FIXED);
           itemDisplay.setItemStack(this.options.item(piece));
           itemDisplay.setInvulnerable(true);
@@ -95,6 +87,46 @@ public void applyToWorld(final ChessBoard board, final BoardStateHolder game, fi
       });
     }
 
+    private static Transformation transformationFor(final ChessBoard board, final Piece piece) {
+      // flip upwards
+      final Quaternionf left = new Quaternionf(new AxisAngle4f((float) Math.toRadians(90.0D), 1, 0, 0));
+      transformForVersion(left);
+      // rotate
+      final Quaternionf right = new Quaternionf(new AxisAngle4f((float) Math.toRadians(rotation(board.facing(), piece)), 0, 0, 1));
+
+      return new Transformation(
+        // center
+        new Vector3f(0.5f * board.scale(), 0, 0.5f * board.scale()),
+        left,
+        // scale
+        new Vector3f(0.5f * board.scale()),
+        right
+      );
+    }
+
+    private static void transformForVersion(final Quaternionf left) {
+      if (Bukkit.getServer().getMinecraftVersion().startsWith("1.19")) {
+        // 1.19.x - nothing to do
+        return;
+      }
+      // 1.20+ - account for 180 flip on y-axis
+      rotateYFlip(left);
+    }
+
+    /**
+     * Transforms the given quaternion in-place to account for the
+     * changes Mojang made to item displays in 1.20.
+     *
+     * @param q quaternion
+     */
+    private static void rotateYFlip(final Quaternionf q) {
+      final float x = q.x, y = q.y, z = q.z, w = q.w;
+      q.x = z;
+      q.y = w;
+      q.z = x;
+      q.w = -y;
+    }
+
     private static float rotation(final CardinalDirection facing, final Piece piece) {
       final double deg = facing.radians() * 180 / Math.PI;
       if (piece.color() == PieceColor.WHITE) {