From a6899f8e6e50d5fa8595649020aacb6ef866eeca Mon Sep 17 00:00:00 2001
From: Walter Bender <walter@sugarlabs.org>
Date: Thu, 09 Sep 2010 14:47:15 +0000
Subject: check alpha value during hit detection

---
(limited to 'TurtleArt/sprites.py')

diff --git a/TurtleArt/sprites.py b/TurtleArt/sprites.py
index bd115e2..47a8121 100644
--- a/TurtleArt/sprites.py
+++ b/TurtleArt/sprites.py
@@ -127,13 +127,14 @@ class Sprites:
         if spr in self.list:
             self.list.remove(spr)
 
-    def find_sprite(self, pos):
+    def find_sprite(self, pos, alpha=True):
         """ Search based on (x, y) position. Return the 'top/first' one. """
         list = self.list[:]
         list.reverse()
         for spr in list:
             if spr.hit(pos):
-                return spr
+                if not alpha or spr.get_pixel(pos)[3] == 255:
+                    return spr
         return None
 
     def refresh(self, event):
--
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