Fix multiple boss bars in 1.8->1.9

1.8 clients only display a single boss bar, so only one tracked bar is attached to the connection at a time. This roughly emulates how the 1.8 client processes the render order (without handling things like the FOV)

common/src/main/java/com/viaversion/viaversion/protocols/v1_8to1_9/rewriter/EntityPacketRewriter1_9.java

@@ -21,6 +21,7 @@ import com.google.common.collect.ImmutableList;
 import com.viaversion.viaversion.api.Via;
 import com.viaversion.viaversion.api.minecraft.EulerAngle;
 import com.viaversion.viaversion.api.minecraft.Vector;
+import com.viaversion.viaversion.api.minecraft.Vector3d;
 import com.viaversion.viaversion.api.minecraft.entities.EntityType;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_9;
 import com.viaversion.viaversion.api.minecraft.entitydata.EntityData;
@@ -112,6 +113,15 @@ public class EntityPacketRewriter1_9 extends EntityRewriter<ClientboundPackets1_
 
                 map(Types.BOOLEAN); // 6 - On Ground
 
+                handler(wrapper -> {
+                    final int entityId = wrapper.get(Types.VAR_INT, 0);
+                    final double x = wrapper.get(Types.DOUBLE, 0);
+                    final double y = wrapper.get(Types.DOUBLE, 1);
+                    final double z = wrapper.get(Types.DOUBLE, 2);
+
+                    final EntityTracker1_9 tracker = wrapper.user().getEntityTracker(protocol);
+                    tracker.setBossPosition(entityId, new Vector3d(x, y, z));
+                });
                 handler(wrapper -> {
                     int entityID = wrapper.get(Types.VAR_INT, 0);
                     if (Via.getConfig().isHologramPatch()) {
@@ -140,6 +150,7 @@ public class EntityPacketRewriter1_9 extends EntityRewriter<ClientboundPackets1_
                 map(Types.BYTE); // 5 - Pitch
 
                 map(Types.BOOLEAN); // 6 - On Ground
+                handler(wrapper -> moveBoss(wrapper, protocol));
             }
         });
         protocol.registerClientbound(ClientboundPackets1_8.MOVE_ENTITY_POS, new PacketHandlers() {
@@ -152,6 +163,7 @@ public class EntityPacketRewriter1_9 extends EntityRewriter<ClientboundPackets1_
                 map(Types.BYTE, toNewShort); // 3 - Z
 
                 map(Types.BOOLEAN); // 4 - On Ground
+                handler(wrapper -> moveBoss(wrapper, protocol));
             }
         });
         protocol.registerClientbound(ClientboundPackets1_8.SET_EQUIPPED_ITEM, new PacketHandlers() {
@@ -379,6 +391,17 @@ public class EntityPacketRewriter1_9 extends EntityRewriter<ClientboundPackets1_
         });
     }
 
+    private static void moveBoss(PacketWrapper wrapper, Protocol1_8To1_9 protocol) {
+        // Deltas were already converted to 1.9 units (1/4096 of a block)
+        final int entityId = wrapper.get(Types.VAR_INT, 0);
+        final double deltaX = wrapper.get(Types.SHORT, 0) / 4096D;
+        final double deltaY = wrapper.get(Types.SHORT, 1) / 4096D;
+        final double deltaZ = wrapper.get(Types.SHORT, 2) / 4096D;
+
+        final EntityTracker1_9 tracker = wrapper.user().getEntityTracker(protocol);
+        tracker.moveBoss(entityId, deltaX, deltaY, deltaZ);
+    }
+
     @Override
     protected void registerRewrites() {
         filter().handler(this::handleEntityData);

common/src/main/java/com/viaversion/viaversion/protocols/v1_8to1_9/rewriter/PlayerPacketRewriter1_9.java

@@ -25,6 +25,7 @@ import com.viaversion.nbt.tag.StringTag;
 import com.viaversion.viaversion.api.Via;
 import com.viaversion.viaversion.api.minecraft.ClientWorld;
 import com.viaversion.viaversion.api.minecraft.GameMode;
+import com.viaversion.viaversion.api.minecraft.Vector3d;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_9;
 import com.viaversion.viaversion.api.minecraft.item.Item;
 import com.viaversion.viaversion.api.protocol.remapper.PacketHandler;
@@ -111,6 +112,17 @@ public class PlayerPacketRewriter1_9 {
 
                 map(Types.BYTE); // 5 - Player Flags
 
+                handler(wrapper -> {
+                    final EntityTracker1_9 tracker = wrapper.user().getEntityTracker(protocol);
+                    final Vector3d position = tracker.getPlayerPosition();
+
+                    final byte flags = wrapper.get(Types.BYTE, 0);
+                    final double x = wrapper.get(Types.DOUBLE, 0) + ((flags & 0x01) != 0 ? position.x() : 0);
+                    final double y = wrapper.get(Types.DOUBLE, 1) + ((flags & 0x02) != 0 ? position.y() : 0);
+                    final double z = wrapper.get(Types.DOUBLE, 2) + ((flags & 0x04) != 0 ? position.z() : 0);
+                    tracker.setPlayerPosition(new Vector3d(x, y, z));
+                });
+
                 create(Types.VAR_INT, 0); // 6 - Teleport ID was added
             }
         });
@@ -449,6 +461,10 @@ public class PlayerPacketRewriter1_9 {
             tracker.incrementIdlePacket();
             tracker.setGround(wrapper.get(Types.BOOLEAN, 0));
         };
+        final PacketHandler positionHandler = wrapper -> {
+            EntityTracker1_9 tracker = wrapper.user().getEntityTracker(protocol);
+            tracker.setPlayerPosition(new Vector3d(wrapper.get(Types.DOUBLE, 0), wrapper.get(Types.DOUBLE, 1), wrapper.get(Types.DOUBLE, 2)));
+        };
         protocol.registerServerbound(ServerboundPackets1_9.MOVE_PLAYER_POS, new PacketHandlers() {
             @Override
             public void register() {
@@ -457,6 +473,7 @@ public class PlayerPacketRewriter1_9 {
                 map(Types.DOUBLE); // 2 - Z
                 map(Types.BOOLEAN); // 3 - Ground
                 handler(onGroundHandler);
+                handler(positionHandler);
             }
         });
         protocol.registerServerbound(ServerboundPackets1_9.MOVE_PLAYER_POS_ROT, new PacketHandlers() {
@@ -469,6 +486,7 @@ public class PlayerPacketRewriter1_9 {
                 map(Types.FLOAT); // 4 - Pitch
                 map(Types.BOOLEAN); // 5 - Ground
                 handler(onGroundHandler);
+                handler(positionHandler);
             }
         });
         protocol.registerServerbound(ServerboundPackets1_9.MOVE_PLAYER_ROT, new PacketHandlers() {

common/src/main/java/com/viaversion/viaversion/protocols/v1_8to1_9/rewriter/SpawnPacketRewriter1_9.java

@@ -18,6 +18,7 @@
 package com.viaversion.viaversion.protocols.v1_8to1_9.rewriter;
 
 import com.viaversion.viaversion.api.data.entity.EntityTracker;
+import com.viaversion.viaversion.api.minecraft.Vector3d;
 import com.viaversion.viaversion.api.minecraft.entities.EntityType;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_8;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_9;
@@ -198,6 +199,17 @@ public class SpawnPacketRewriter1_9 {
                 map(Types.SHORT); // 10 - Velocity Y
                 map(Types.SHORT); // 11 - Velocity Z
 
+                // Has to happen before the entity data is handled, which may create the boss bar
+                handler(wrapper -> {
+                    final int entityId = wrapper.get(Types.VAR_INT, 0);
+                    final double x = wrapper.get(Types.DOUBLE, 0);
+                    final double y = wrapper.get(Types.DOUBLE, 1);
+                    final double z = wrapper.get(Types.DOUBLE, 2);
+
+                    final EntityTracker1_9 tracker = wrapper.user().getEntityTracker(protocol);
+                    tracker.setBossPosition(entityId, new Vector3d(x, y, z));
+                });
+
                 map(Types.ENTITY_DATA_LIST1_8, Types.ENTITY_DATA_LIST1_9);
                 handler(wrapper -> {
                     List<EntityData> entityDataList = wrapper.get(Types.ENTITY_DATA_LIST1_9, 0);

common/src/main/java/com/viaversion/viaversion/protocols/v1_8to1_9/storage/EntityTracker1_9.java

@@ -26,6 +26,7 @@ import com.viaversion.viaversion.api.legacy.bossbar.BossColor;
 import com.viaversion.viaversion.api.legacy.bossbar.BossStyle;
 import com.viaversion.viaversion.api.minecraft.BlockPosition;
 import com.viaversion.viaversion.api.minecraft.GameMode;
+import com.viaversion.viaversion.api.minecraft.Vector3d;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_9.EntityType;
 import com.viaversion.viaversion.api.minecraft.entitydata.EntityData;
 import com.viaversion.viaversion.api.minecraft.entitydata.types.EntityDataTypes1_9;
@@ -58,9 +59,15 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 public class EntityTracker1_9 extends EntityTrackerBase {
     public static final String WITHER_TRANSLATABLE = "{\"translate\":\"entity.WitherBoss.name\"}";
     public static final String DRAGON_TRANSLATABLE = "{\"translate\":\"entity.EnderDragon.name\"}";
+    // 1.8 Entity#isInRangeToRenderDist: average bounding box edge length * 64
+    private static final double WITHER_RENDER_DISTANCE = (0.9 + 3.5 + 0.9) / 3 * 64;
+    private static final double DRAGON_RENDER_DISTANCE = (16.0 + 8.0 + 16.0) / 3 * 64;
     private final Int2ObjectMap<UUID> uuidMap = new Int2ObjectOpenHashMap<>();
     private final Int2IntMap vehicleMap = new Int2IntOpenHashMap();
     private final Int2ObjectMap<BossBar> bossBarMap = new Int2ObjectOpenHashMap<>();
+    private final Int2ObjectMap<Vector3d> bossPositions = new Int2ObjectOpenHashMap<>();
+    private BossBar shownBossBar;
+    private Vector3d playerPosition = Vector3d.ZERO;
     private final IntSet validBlocking = new IntOpenHashSet();
     private final IntSet knownHolograms = new IntOpenHashSet();
     private final Set<BlockPosition> blockInteractions = Collections.newSetFromMap(CacheBuilder.newBuilder()
@@ -143,16 +150,92 @@ public class EntityTracker1_9 extends EntityTrackerBase {
         validBlocking.remove(entityId);
         knownHolograms.remove(entityId);
 
-        BossBar bar = bossBarMap.remove(entityId);
-        if (bar != null) {
-            bar.hide();
-            // Send to provider
-            Via.getManager().getProviders().get(BossBarProvider.class).handleRemove(user(), bar.getId());
+        this.bossPositions.remove(entityId);
+        BossBar bar = this.bossBarMap.remove(entityId);
+        if (bar != null && bar == this.shownBossBar) {
+            this.updateShownBossBar();
         }
 
         return super.removeEntity(entityId);
     }
 
+    public void setBossPosition(final int entityId, final Vector3d position) {
+        final com.viaversion.viaversion.api.minecraft.entities.EntityType type = this.entityType(entityId);
+        if (type != EntityType.WITHER && type != EntityType.ENDER_DRAGON) {
+            return;
+        }
+
+        this.bossPositions.put(entityId, position);
+        this.updateShownBossBar();
+    }
+
+    public void moveBoss(final int entityId, final double deltaX, final double deltaY, final double deltaZ) {
+        final Vector3d position = this.bossPositions.get(entityId);
+        if (position != null) {
+            this.setBossPosition(entityId, new Vector3d(position.x() + deltaX, position.y() + deltaY, position.z() + deltaZ));
+        }
+    }
+
+    public Vector3d getPlayerPosition() {
+        return this.playerPosition;
+    }
+
+    public void setPlayerPosition(final Vector3d playerPosition) {
+        this.playerPosition = playerPosition;
+        this.updateShownBossBar();
+    }
+
+    private void updateShownBossBar() {
+        BossBar best = null;
+        int bestSectionDistance = -1;
+        for (final Int2ObjectMap.Entry<BossBar> entry : this.bossBarMap.int2ObjectEntrySet()) {
+            final Vector3d position = this.bossPositions.get(entry.getIntKey());
+            if (position == null) {
+                continue;
+            }
+
+            final double deltaX = position.x() - this.playerPosition.x();
+            final double deltaY = position.y() - this.playerPosition.y();
+            final double deltaZ = position.z() - this.playerPosition.z();
+            final double range = this.entityType(entry.getIntKey()) == EntityType.ENDER_DRAGON ? DRAGON_RENDER_DISTANCE : WITHER_RENDER_DISTANCE;
+            if (deltaX * deltaX + deltaY * deltaY + deltaZ * deltaZ >= range * range) {
+                continue;
+            }
+
+            final int distanceX = Math.abs(sectionCoord(position.x()) - sectionCoord(this.playerPosition.x()));
+            final int distanceY = Math.abs(sectionCoord(position.y()) - sectionCoord(this.playerPosition.y()));
+            final int distanceZ = Math.abs(sectionCoord(position.z()) - sectionCoord(this.playerPosition.z()));
+            final int sectionDistance = distanceX + distanceY + distanceZ;
+            // Prefer the currently shown bar on ties to avoid needless switching
+            if (sectionDistance > bestSectionDistance || (sectionDistance == bestSectionDistance && entry.getValue() == shownBossBar)) {
+                best = entry.getValue();
+                bestSectionDistance = sectionDistance;
+            }
+        }
+        this.showBossBar(best);
+    }
+
+    private static int sectionCoord(double coord) {
+        return (int) Math.floor(coord) >> 4;
+    }
+
+    private void showBossBar(@Nullable final BossBar bar) {
+        if (bar == this.shownBossBar) {
+            return;
+        }
+
+        final BossBarProvider provider = Via.getManager().getProviders().get(BossBarProvider.class);
+        if (this.shownBossBar != null) {
+            this.shownBossBar.removeConnection(user());
+            provider.handleRemove(user(), this.shownBossBar.getId());
+        }
+        this.shownBossBar = bar;
+        if (bar != null) {
+            bar.addConnection(user());
+            provider.handleAdd(user(), bar.getId());
+        }
+    }
+
     public boolean interactedBlockRecently(final int x, final int y, final int z) {
         for (final BlockPosition position : blockInteractions) {
             if (Math.abs(position.x() - x) <= 1 && Math.abs(position.y() - y) <= 1 && Math.abs(position.z() - z) <= 1) {
@@ -253,11 +336,7 @@ public class EntityTracker1_9 extends EntityTrackerBase {
                         if (bar == null) {
                             bar = Via.getAPI().legacyAPI().createLegacyBossBar(title, BossColor.PINK, BossStyle.SOLID);
                             bossBarMap.put(entityId, bar);
-                            bar.addConnection(user());
-                            bar.show();
-
-                            // Send to provider
-                            Via.getManager().getProviders().get(BossBarProvider.class).handleAdd(user(), bar.getId());
+                            updateShownBossBar();
                         } else {
                             bar.setTitle(title);
                         }
@@ -270,10 +349,7 @@ public class EntityTracker1_9 extends EntityTrackerBase {
                             String title = type == EntityType.ENDER_DRAGON ? DRAGON_TRANSLATABLE : WITHER_TRANSLATABLE;
                             bar = Via.getAPI().legacyAPI().createLegacyBossBar(title, health, BossColor.PINK, BossStyle.SOLID);
                             bossBarMap.put(entityId, bar);
-                            bar.addConnection(user());
-                            bar.show();
-                            // Send to provider
-                            Via.getManager().getProviders().get(BossBarProvider.class).handleAdd(user(), bar.getId());
+                            updateShownBossBar();
                         } else {
                             bar.setHealth(health);
                         }