Added a command to turn it on/off

worldedit-core/src/main/java/com/sk89q/worldedit/LocalSession.java

@@ -618,6 +618,14 @@ public class LocalSession {
     public void tellVersion(Actor player) {
     }
 
+    public boolean shouldUseServerCUI() {
+        return this.useServerCUI;
+    }
+
+    public void setUseServerCUI(boolean useServerCUI) {
+        this.useServerCUI = useServerCUI;
+    }
+
     /**
      * Update server-side WorldEdit CUI.
      *
@@ -628,12 +636,16 @@ public class LocalSession {
             return; // This is for players only.
         }
 
+        Player player = (Player) actor;
+
         if (!useServerCUI || hasCUISupport) {
+            if (cuiTemporaryBlock != null) {
+                player.sendFakeBlock(cuiTemporaryBlock, null);
+                cuiTemporaryBlock = null;
+            }
             return; // If it's not enabled, ignore this.
         }
 
-        Player player = (Player) actor;
-
         // Remove the old block.
         if (cuiTemporaryBlock != null) {
             player.sendFakeBlock(cuiTemporaryBlock, null);

worldedit-core/src/main/java/com/sk89q/worldedit/command/GeneralCommands.java

@@ -114,6 +114,38 @@ public class GeneralCommands {
         }
     }
 
+    @Command(
+            aliases = { "/drawsel" },
+            usage = "[on|off]",
+            desc = "Toggle drawing the current selection",
+            min = 0,
+            max = 1
+    )
+    @CommandPermissions("worldedit.drawsel")
+    public void drawSelection(Player player, LocalSession session, CommandContext args) throws WorldEditException {
+
+        String newState = args.getString(0, null);
+        if (session.shouldUseServerCUI()) {
+            if ("on".equals(newState)) {
+                player.printError("Server CUI already enabled.");
+                return;
+            }
+
+            session.setUseServerCUI(false);
+            session.updateServerCUI(player);
+            player.print("Server CUI disabled.");
+        } else {
+            if ("off".equals(newState)) {
+                player.printError("Server CUI already disabled.");
+                return;
+            }
+
+            session.setUseServerCUI(true);
+            session.updateServerCUI(player);
+            player.print("Server CUI enabled. This only supports cuboid regions, with a maximum size of 32x32x32.");
+        }
+    }
+
     @Command(
         aliases = { "/gmask", "gmask" },
         usage = "[mask]",