From 25320dff083ef6dfeadf416956353bc42cd7d54c Mon Sep 17 00:00:00 2001
From: Walter Bender <walter@sugarlabs.org>
Date: Wed, 20 Oct 2010 00:09:19 +0000
Subject: only allow one start, hat1, or hat2 block per project

---
diff --git a/TurtleArt/tablock.py b/TurtleArt/tablock.py
index 344f2da..865e8e9 100644
--- a/TurtleArt/tablock.py
+++ b/TurtleArt/tablock.py
@@ -113,6 +113,12 @@ class Blocks:
             i += 1
         return None
 
+    def get_block_of_same_type_and_name(self, type, name):
+        for block in self.list:
+            if block.type == type and block.name == name:
+                return block
+        return None
+
 
 class Block:
     """ A class for the individual blocks """
diff --git a/TurtleArt/tawindow.py b/TurtleArt/tawindow.py
index 1bc7ab8..2853bbd 100644
--- a/TurtleArt/tawindow.py
+++ b/TurtleArt/tawindow.py
@@ -782,6 +782,11 @@ class TurtleArtWindow():
                 elif blk.name in MACROS:
                     self._new_macro(blk.name, x + 20, y + 20)
                 else:
+                    # You can only have one instance of some blocks
+                    if blk.name in ['start', 'hat1', 'hat2']:
+                        if self.block_list.get_block_of_same_type_and_name(
+                            'block', blk.name) is not None:
+                            return True
                     blk.highlight()
                     self._new_block(blk.name, x, y)
                     blk.unhighlight()
--
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