Undid PosCenter change

Terminal.Gui/View/Layout/PosCenter.cs

@@ -16,6 +16,6 @@ public class PosCenter : Pos
         // Protect against negative dimensions
         int newDimension = Math.Max (dim.Calculate (0, superviewDimension, us, dimension), 0);
 
-        return superviewDimension / 2 - newDimension / 2;
+        return (superviewDimension - newDimension) / 2;
     }
 }

UnitTests/View/Layout/Dim.AutoTests.cs

@@ -1296,8 +1296,8 @@ public class DimAutoTests (ITestOutputHelper output)
         view.BeginInit ();
         view.EndInit ();
         // subview should be centered in the parent view + 1
-        Assert.Equal (view.Viewport.Width / 2 - subview.Frame.Width / 2, subview.Frame.X);
-        Assert.Equal (view.Viewport.Height / 2 - subview.Frame.Height / 2, subview.Frame.Y);
+        Assert.Equal ((view.Viewport.Width - subview.Frame.Width) / 2, subview.Frame.X);
+        Assert.Equal ((view.Viewport.Height - subview.Frame.Height) / 2, subview.Frame.Y);
     }
 
     [Theory]
@@ -1340,8 +1340,8 @@ public class DimAutoTests (ITestOutputHelper output)
         view.BeginInit ();
         view.EndInit ();
         // subview should be centered in the parent view + 1
-        Assert.Equal (view.Viewport.Width / 2 - subview.Frame.Width / 2 + 1, subview.Frame.X);
-        Assert.Equal (view.Viewport.Height / 2 - subview.Frame.Height / 2 + 1, subview.Frame.Y);
+        Assert.Equal ((view.Viewport.Width - subview.Frame.Width) / 2  + 1, subview.Frame.X);
+        Assert.Equal ((view.Viewport.Height - subview.Frame.Height) / 2 + 1, subview.Frame.Y);
     }
 
     [Theory]