From 1bd6ad3543426ca11b21b7c8ed5ca5d05c1d60dc Mon Sep 17 00:00:00 2001
From: Michael Smith <mike@mikelikescoding.com>
Date: Wed, 17 Feb 2016 22:57:20 -0800
Subject: [PATCH] + Updated Difference's Position() behavior to return the
 position of the first child (object being differenced)

---
 OSCADSharp/OSCADSharp.ConsoleTests/Program.cs  | 16 ++++++----------
 .../OSCADSharp.UnitTests/DifferenceTests.cs    | 18 +++++++++++++-----
 OSCADSharp/OSCADSharp/Booleans/Difference.cs   |  2 +-
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/OSCADSharp/OSCADSharp.ConsoleTests/Program.cs b/OSCADSharp/OSCADSharp.ConsoleTests/Program.cs
index 40907f9..ea57b78 100644
--- a/OSCADSharp/OSCADSharp.ConsoleTests/Program.cs
+++ b/OSCADSharp/OSCADSharp.ConsoleTests/Program.cs
@@ -13,19 +13,15 @@ namespace OSCADSharp.ConsoleTests
     {
         static void Main(string[] args)
         {
-            //var obj = new Cube(5, 10, 20).Mirror(0, 0, 1).Mirror(0, 1, 0)
-            //    .Rotate(15, -45, 120).Translate(-20, 10, 15).Rotate(90, 15, 25)
-            //    .Translate(-10, -20, -20).Rotate(-90, -90, -45);
-
             var obj = new Cube() + new Sphere() + new Sphere().Translate(2, 2, 2) - new Cylinder(2, 5) + new Text3D("Hey hey!");
 
-            //var pos = obj.Position();
-            //var cyl1 = new Cylinder(1, 100, true).Translate(pos);
-            //var cyl2 = new Cylinder(1, 100, true).Rotate(0, 90, 0).Translate(pos);
-            //var cyl3 = new Cylinder(1, 100, true).Rotate(90, 0, 0).Translate(pos);
-            //var axisHelper = cyl1.Union(cyl2, cyl3).Color("Red");
+            var pos = obj.Position();
+            var cyl1 = new Cylinder(1, 100, true).Translate(pos);
+            var cyl2 = new Cylinder(1, 100, true).Rotate(0, 90, 0).Translate(pos);
+            var cyl3 = new Cylinder(1, 100, true).Rotate(90, 0, 0).Translate(pos);
+            var axisHelper = cyl1.Union(cyl2, cyl3).Color("Red");
 
-            string script = obj.ToString(); //obj.Union(axisHelper).ToString();
+            string script = obj.Union(axisHelper).ToString();
 
             File.WriteAllLines("test.scad", new string[] { script.ToString() });
             //Console.ReadKey();
diff --git a/OSCADSharp/OSCADSharp.UnitTests/DifferenceTests.cs b/OSCADSharp/OSCADSharp.UnitTests/DifferenceTests.cs
index 391dccf..10aeaa1 100644
--- a/OSCADSharp/OSCADSharp.UnitTests/DifferenceTests.cs
+++ b/OSCADSharp/OSCADSharp.UnitTests/DifferenceTests.cs
@@ -8,13 +8,21 @@ namespace OSCADSharp.UnitTests
     [TestClass]
     public class DifferenceTests
     {
-        [TestMethod]
-        [ExpectedException(typeof(NotSupportedException))]
-        public void Difference_PositionThrowsNotSupportedException()
+        /// <summary>
+        /// Note:  The decision that Difference should yield the position of the
+        /// first child stems from the common use case of using Difference to bore out
+        /// holes for pegs, screws, supports, etc.  It's often used in such a way that 
+        /// the overall structure of the object being differenced is not greatly affected,
+        /// thus the position should not change.
+        /// -MLS 2/17/2016
+        /// </summary>
+        [TestMethod]     
+        public void Difference_PositionYieldsPositionOfFirstChild()
         {
-            var diff = new Sphere().Difference(new Cube());
+            var sphere = new Sphere().Translate(.25, .25, 1);
+            var diff = sphere.Difference(new Cube());
 
-            var pos = diff.Position();
+            Assert.AreEqual(sphere.Position(), diff.Position());
         }
 
         [TestMethod]
diff --git a/OSCADSharp/OSCADSharp/Booleans/Difference.cs b/OSCADSharp/OSCADSharp/Booleans/Difference.cs
index bd66924..6b00007 100644
--- a/OSCADSharp/OSCADSharp/Booleans/Difference.cs
+++ b/OSCADSharp/OSCADSharp/Booleans/Difference.cs
@@ -22,7 +22,7 @@ namespace OSCADSharp.Booleans
 
         public override Vector3 Position()
         {
-            throw new NotSupportedException("Position is not supported on Differenced objects.");
+            return children[0].Position();
         }
     }
 }