Added WECUI protocol version support. Eventually, this will disable WECUI until the user updates, but not yet.

src/main/java/com/sk89q/worldedit/commands/WorldEditCommands.java

@@ -32,6 +32,7 @@ import com.sk89q.worldedit.LocalPlayer;
 import com.sk89q.worldedit.LocalSession;
 import com.sk89q.worldedit.WorldEdit;
 import com.sk89q.worldedit.WorldEditException;
+import com.sk89q.worldedit.cui.CUIEvent;
 
 public class WorldEditCommands {
     private static final DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss z");
@@ -78,10 +79,13 @@ public class WorldEditCommands {
         usage = "",
         desc = "Complete CUI handshake",
         min = 0,
-        max = 0
+        max = 1
     )
     public void cui(CommandContext args, LocalSession session, LocalPlayer player,
             EditSession editSession) throws WorldEditException {
+        if (args.getInteger(0, -1) < CUIEvent.MIN_PROTOCOL) {
+            player.printError("You are using an outdated version of WorldEdit CUI! The CUI may have reduced functionality until you update.");
+        }
         session.setCUISupport(true);
         session.dispatchCUISetup(player);
     }

src/main/java/com/sk89q/worldedit/cui/CUIEvent.java

@@ -20,6 +20,10 @@
 package com.sk89q.worldedit.cui;
 
 public interface CUIEvent {
+
+    // The required protocol versions for communicating with the CUI
+    public static final int MIN_PROTOCOL = 0, CURRENT_PROTOCOL = 0;
+
     public String getTypeId();
 
     public String[] getParameters();