fix: item lines not showing to players upon joining (#204)

src/main/java/eu/decentsoftware/holograms/api/DecentHolograms.java

@@ -4,6 +4,7 @@
 import eu.decentsoftware.holograms.api.commands.CommandManager;
 import eu.decentsoftware.holograms.api.features.FeatureManager;
 import eu.decentsoftware.holograms.api.holograms.Hologram;
+import eu.decentsoftware.holograms.api.holograms.HologramLineDisplayHandler;
 import eu.decentsoftware.holograms.api.holograms.HologramManager;
 import eu.decentsoftware.holograms.api.nms.NMS;
 import eu.decentsoftware.holograms.api.nms.PacketListener;
@@ -44,10 +45,12 @@ public final class DecentHolograms {
 
     private final JavaPlugin plugin;
     private HologramManager hologramManager;
+    private HologramLineDisplayHandler lineDisplayHandler;
     private CommandManager commandManager;
     private FeatureManager featureManager;
     private AnimationManager animationManager;
     private PacketListener packetListener;
+    private PlayerListener playerListener;
     private Ticker ticker;
     private boolean updateAvailable;
 
@@ -80,13 +83,14 @@ void enable() {
 
         this.ticker = new Ticker();
         this.hologramManager = new HologramManager(this);
+        this.lineDisplayHandler = new HologramLineDisplayHandler();
         this.commandManager = new CommandManager();
         this.featureManager = new FeatureManager();
         this.animationManager = new AnimationManager(this);
         this.packetListener = new PacketListener(this);
 
         PluginManager pm = Bukkit.getPluginManager();
-        pm.registerEvents(new PlayerListener(this), this.plugin);
+        pm.registerEvents((playerListener = new PlayerListener(this)), this.plugin);
         pm.registerEvents(new WorldListener(this), this.plugin);
 
         // Setup metrics

src/main/java/eu/decentsoftware/holograms/api/Settings.java

@@ -34,6 +34,8 @@ public class Settings {
     public static double DEFAULT_HEIGHT_SMALLHEAD = 0.6;
     @Key(value = "defaults.display-range", min = 1, max = 48)
     public static int DEFAULT_DISPLAY_RANGE = 48;
+    @Key(value = "defaults.item-display-range", min = 1, max = 48)
+    public static int DEFAULT_ITEM_DISPLAY_RANGE = 16;
     @Key(value = "defaults.update-range", min = 1, max = 48)
     public static int DEFAULT_UPDATE_RANGE = 48;
     @Key(value = "defaults.update-interval", min = 1, max = 1200)
@@ -42,6 +44,8 @@ public class Settings {
     public static int DEFAULT_LRU_CACHE_SIZE = 500;
     @Key("allow-placeholders-inside-animations")
     public static boolean ALLOW_PLACEHOLDERS_INSIDE_ANIMATIONS = false;
+    @Key(value = "defaults.minimum-session-ticks-item-line", min = 0)
+    public static int DEFAULT_MINIMUM_SESSION_TICKS_ITEM_LINE = 40;
 
     public static Map<String, String> CUSTOM_REPLACEMENTS = ImmutableMap.<String, String>builder()
             .put("[x]", "\u2588")

src/main/java/eu/decentsoftware/holograms/api/holograms/Hologram.java

@@ -633,14 +633,10 @@ public boolean show(@NonNull Player player, int pageIndex) {
             if (page != null && page.size() > 0 && canShow(player) && isInDisplayRange(player)) {
                 if (isVisible(player)) {
                     hide(player);
+                    return true; // Skip a tick before updating, should fix the previous issue with clients desyncing.
                 }
-                if (Version.after(8)) {
-                    showPageTo(player, page, pageIndex);
-                } else {
-                    // We need to run the task later on older versions as, if we don't, it causes issues with some holograms *randomly* becoming invisible.
-                    // I *think* this is from despawning and spawning the entities (with the same ID) in the same tick.
-                    S.sync(() -> showPageTo(player, page, pageIndex), 0L);
-                }
+
+                showPageTo(player, page, pageIndex);
                 return true;
             }
             return false;

src/main/java/eu/decentsoftware/holograms/api/holograms/HologramLine.java

@@ -409,6 +409,9 @@ public void show(Player... players) {
             if (parent != null && parent.getParent().isHideState(player)) {
                 continue;
             }
+
+            DECENT_HOLOGRAMS.getLineDisplayHandler().removeFromQueue(this, player);
+
             if (!isVisible(player) && canShow(player) && isInDisplayRange(player)) {
                 switch (type) {
                     case TEXT:
@@ -418,14 +421,11 @@ public void show(Player... players) {
                     case HEAD:
                     case SMALLHEAD:
                         nms.showFakeEntityArmorStand(player, getLocation(), entityIds[0], true, HologramLineType.HEAD != type, false);
-                        ItemStack itemStack = containsPlaceholders ? HologramItem.parseItemStack(item.getContent(), player) : item.parse();
-                        nms.helmetFakeEntity(player, itemStack, entityIds[0]);
+                        DECENT_HOLOGRAMS.getLineDisplayHandler().queue(this, player);
                         break;
                     case ICON:
                         nms.showFakeEntityArmorStand(player, getLocation(), entityIds[0], true, true, false);
-                        ItemStack itemStack1 = containsPlaceholders ? HologramItem.parseItemStack(item.getContent(), player) : item.parse();
-                        nms.showFakeEntityItem(player, getLocation(), itemStack1, entityIds[1]);
-                        nms.attachFakeEntity(player, entityIds[0], entityIds[1]);
+                        DECENT_HOLOGRAMS.getLineDisplayHandler().queue(this, player);
                         break;
                     case ENTITY:
                         EntityType entityType = new HologramEntity(PAPI.setPlaceholders(player, getEntity().getContent())).getType();
@@ -447,6 +447,26 @@ public void show(Player... players) {
         }
     }
 
+    protected void showItem(Player player) {
+        if (!viewers.contains(player.getUniqueId())) {
+            return;
+        }
+
+        NMS nms = NMS.getInstance();
+
+        switch (type) {
+            case HEAD:
+            case SMALLHEAD:
+                ItemStack itemStack = containsPlaceholders ? HologramItem.parseItemStack(item.getContent(), player) : item.parse();
+                nms.helmetFakeEntity(player, itemStack, entityIds[0]);
+                break;
+            case ICON:
+                ItemStack itemStack1 = containsPlaceholders ? HologramItem.parseItemStack(item.getContent(), player) : item.parse();
+                nms.showFakeEntityItem(player, getLocation(), itemStack1, entityIds[1]);
+                nms.attachFakeEntity(player, entityIds[0], entityIds[1]);
+        }
+    }
+
     /**
      * Update this line for given players.
      *
@@ -519,6 +539,7 @@ public void updateAnimations(Player... players) {
     public void hide(Player... players) {
         List<Player> playerList = getPlayers(true, players);
         for (Player player : playerList) {
+            DECENT_HOLOGRAMS.getLineDisplayHandler().removeFromQueue(this, player);
             NMS.getInstance().hideFakeEntities(player, entityIds[0], entityIds[1]);
             viewers.remove(player.getUniqueId());
         }
@@ -565,10 +586,4 @@ public void setOffsetZ(double offsetZ) {
     public boolean hasFlag(@NonNull EnumFlag flag) {
         return super.hasFlag(flag) || (parent != null && parent.getParent().hasFlag(flag));
     }
-
-    @Override
-    public boolean canShow(@NonNull Player player) {
-        return super.canShow(player) && (parent == null || parent.getParent().canShow(player));
-    }
-
 }

src/main/java/eu/decentsoftware/holograms/api/holograms/HologramLineDisplayHandler.java

@@ -0,0 +1,107 @@
+package eu.decentsoftware.holograms.api.holograms;
+
+import eu.decentsoftware.holograms.api.DecentHologramsAPI;
+import eu.decentsoftware.holograms.api.Settings;
+import eu.decentsoftware.holograms.api.utils.tick.Ticked;
+import lombok.Getter;
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+
+import java.util.LinkedHashSet;
+import java.util.Queue;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.TimeUnit;
+
+public class HologramLineDisplayHandler extends Ticked {
+
+    private static final long TTL = TimeUnit.SECONDS.toMillis(30);
+    private static final int MAX_QUEUE_SIZE = 10_000;
+
+    private final Queue<LineDisplayEntry> queue = new ConcurrentLinkedQueue<>();
+
+    public HologramLineDisplayHandler() {
+        super(1L);
+        this.register();
+    }
+
+    public void queue(HologramLine line, Player player) {
+        if (queue.stream().anyMatch(entry -> entry.getLine() == line && player.getUniqueId().equals(entry.getPlayerId()))) {
+            return;
+        }
+
+        queue.add(new LineDisplayEntry(line, player.getUniqueId()));
+    }
+
+    public void removeFromQueue(HologramLine line, Player player) {
+        queue.removeIf(entry -> entry.getLine() == line && player.getUniqueId().equals(entry.getPlayerId()));
+    }
+
+    @Override
+    public void tick() {
+        final Set<UUID> playersUpdated = new LinkedHashSet<>(); // We only want to send the player one item per tick
+        final Set<LineDisplayEntry> reQueue = new LinkedHashSet<>();
+
+        while (!queue.isEmpty()) {
+            LineDisplayEntry poll = queue.poll();
+
+            if (poll == null) {
+                continue;
+            }
+
+            if (System.currentTimeMillis() - poll.getTimestamp() > TTL) {
+                continue;
+            }
+
+            Player player = Bukkit.getPlayer(poll.getPlayerId());
+
+            if (player == null) {
+                continue;
+            }
+
+            if (playersUpdated.contains(player.getUniqueId())) {
+                reQueue.add(poll);
+                continue;
+            }
+
+            HologramLine line = poll.getLine();
+
+            if (!line.isVisible(player)) {
+                continue;
+            }
+
+            if (canDisplay(player)) {
+                line.showItem(player);
+                playersUpdated.add(player.getUniqueId());
+            } else {
+                reQueue.add(poll);
+            }
+        }
+
+        queue.addAll(reQueue);
+        playersUpdated.clear();
+        reQueue.clear();
+
+        if (queue.size() >= MAX_QUEUE_SIZE) {
+            queue.clear();
+        }
+    }
+
+    private boolean canDisplay(Player player) {
+        return DecentHologramsAPI.get().getPlayerListener().getTicksSinceLogin(player) >= Settings.DEFAULT_MINIMUM_SESSION_TICKS_ITEM_LINE;
+    }
+
+    @Getter
+    private static class LineDisplayEntry {
+
+        private final HologramLine line;
+        private final UUID playerId;
+        private final long timestamp = System.currentTimeMillis();
+
+        public LineDisplayEntry(HologramLine line, UUID playerId) {
+            this.line = line;
+            this.playerId = playerId;
+        }
+    }
+}

src/main/java/eu/decentsoftware/holograms/api/holograms/HologramManager.java

@@ -8,6 +8,7 @@
 import eu.decentsoftware.holograms.api.utils.file.FileUtils;
 import eu.decentsoftware.holograms.api.utils.scheduler.S;
 import eu.decentsoftware.holograms.api.utils.tick.Ticked;
+import lombok.Getter;
 import lombok.NonNull;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
@@ -68,6 +69,13 @@ public void updateVisibility(@NonNull Player player) {
         }
     }
 
+    /**
+     * Update the visibility of the hologram for the given player.
+     *
+     * @param player - The player to update the visibility for.
+     * @param hologram - The hologram to update the visibility for.
+     * @return True if the hologram was shown, false otherwise.
+     */
     public void updateVisibility(@NonNull Player player, @NonNull Hologram hologram) {
         if (hologram.isDisabled()) {
             return;

src/main/java/eu/decentsoftware/holograms/api/listeners/PlayerListener.java

@@ -12,10 +12,15 @@
 import org.bukkit.event.player.PlayerRespawnEvent;
 import org.bukkit.event.player.PlayerTeleportEvent;
 
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+
 @SuppressWarnings("unused")
 public class PlayerListener implements Listener {
 
     private final DecentHolograms decentHolograms;
+    private final Map<UUID, Long> playerLoginTime = new ConcurrentHashMap<>(); // Hologram lines can be updated asynchronously
 
     public PlayerListener(DecentHolograms decentHolograms) {
         this.decentHolograms = decentHolograms;
@@ -24,18 +29,20 @@ public PlayerListener(DecentHolograms decentHolograms) {
     @EventHandler(priority = EventPriority.MONITOR)
     public void onJoin(PlayerJoinEvent e) {
         Player player = e.getPlayer();
-        S.async(() -> decentHolograms.getHologramManager().updateVisibility(player));
         decentHolograms.getPacketListener().hook(player);
         if (decentHolograms.isUpdateAvailable() && player.hasPermission("dh.admin")) {
             Lang.sendUpdateMessage(player);
         }
+
+        playerLoginTime.put(player.getUniqueId(), System.currentTimeMillis());
     }
 
     @EventHandler
     public void onQuit(PlayerQuitEvent e) {
         Player player = e.getPlayer();
         S.async(() -> decentHolograms.getHologramManager().onQuit(player));
         decentHolograms.getPacketListener().unhook(player);
+        playerLoginTime.remove(player.getUniqueId());
     }
 
     @EventHandler
@@ -59,4 +66,13 @@ public void onTeleport(PlayerTeleportEvent e) {
         S.async(() -> decentHolograms.getHologramManager().hideAll(player));
     }
 
+    public int getTicksSinceLogin(Player player) {
+        Long epoch = playerLoginTime.get(player.getUniqueId());
+
+        if (epoch == null) {
+            return 0;
+        }
+
+        return (int) ((System.currentTimeMillis() - epoch)) / 50;
+    }
 }