Improved PacketWindowItems and DisplayFrame

eco-core/core-plugin/src/main/kotlin/com/willfp/eco/internal/spigot/display/PacketWindowItems.kt

@@ -14,7 +14,7 @@ import org.bukkit.inventory.ItemStack
 import java.util.concurrent.ConcurrentHashMap
 
 class PacketWindowItems(plugin: EcoPlugin) : AbstractPacketAdapter(plugin, PacketType.Play.Server.WINDOW_ITEMS, false) {
-    private val ignorePacketList = ConcurrentHashMap.newKeySet<String>()
+    private val lastKnownWindowIDs = ConcurrentHashMap<String, Int>()
 
     override fun onSend(
         packet: PacketContainer,
@@ -27,19 +27,19 @@ class PacketWindowItems(plugin: EcoPlugin) : AbstractPacketAdapter(plugin, Packe
             )
         }
 
-        if (ignorePacketList.contains(player.name)) {
-            ignorePacketList.remove(player.name)
-            return
-        }
-
         val windowId = packet.integers.read(0)
 
-        // TODO
-        /*
-        Bug here is that sometimes a non-zero window ID packet is then proceeded by three
-        zero ones, causing display frame bugs.
-         */
-        if (windowId != 0) {
+        // Using name because UUID is unreliable with ProtocolLib players.
+        val name = player.name
+
+        val lastKnownID = lastKnownWindowIDs[name]
+        lastKnownWindowIDs[name] = windowId
+
+        // If there is any change in window ID at any point,
+        // Remove the last display frame to prevent any potential conflicts.
+        // If the window ID is not zero (not a player inventory), then remove too,
+        // as GUIs are not player inventories.
+        if (lastKnownID != windowId || windowId != 0) {
             player.lastDisplayFrame = DisplayFrame.EMPTY
         }