From 14f01a53dad505563c558ff295aa67058442c415 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 26 Mar 2016 16:32:14 +0100
Subject: [PATCH] Set D2D RenderTarget DPI.

---
 src/Windows/Perspex.Direct2D1/RenderTarget.cs | 23 ++++++++-----------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/src/Windows/Perspex.Direct2D1/RenderTarget.cs b/src/Windows/Perspex.Direct2D1/RenderTarget.cs
index 0d66ba99bd..2c303ffacb 100644
--- a/src/Windows/Perspex.Direct2D1/RenderTarget.cs
+++ b/src/Windows/Perspex.Direct2D1/RenderTarget.cs
@@ -15,6 +15,7 @@ namespace Perspex.Direct2D1
     {
         private readonly IntPtr _hwnd;
         private Size2 _savedSize;
+        private Size2F _savedDpi;
 
         /// <summary>
         /// The render target.
@@ -82,28 +83,24 @@ namespace Perspex.Direct2D1
         public DrawingContext CreateDrawingContext()
         {
             var window = _renderTarget as WindowRenderTarget;
-            var factor = 1.0;
 
             if (window != null)
             {
                 var size = GetWindowSize();
-                factor = GetWindowScaling();
+                var dpi = GetWindowDpi();
 
                 if (size != _savedSize)
                 {
                     window.Resize(_savedSize = size);
                 }
-            }
-
-            var ctx = new DrawingContext(new Media.DrawingContext(_renderTarget, DirectWriteFactory));
 
-            if (factor != 1)
-            {
-                ctx.PushPostTransform(Matrix.CreateScale(factor, factor));
-                ctx.PushTransformContainer();
+                if (dpi != _savedDpi)
+                {
+                    window.DotsPerInch = _savedDpi = dpi;
+                }
             }
 
-            return ctx;
+            return new DrawingContext(new Media.DrawingContext(_renderTarget, DirectWriteFactory));
         }
 
         public void Dispose()
@@ -111,7 +108,7 @@ namespace Perspex.Direct2D1
             _renderTarget.Dispose();
         }
 
-        private double GetWindowScaling()
+        private Size2F GetWindowDpi()
         {
             if (UnmanagedMethods.ShCoreAvailable)
             {
@@ -127,11 +124,11 @@ namespace Perspex.Direct2D1
                         out dpix,
                         out dpiy) == 0)
                 {
-                    return dpix / 96.0;
+                    return new Size2F(dpix, dpiy);
                 }
             }
 
-            return 1;
+            return new Size2F(1, 1);
         }
 
         private Size2 GetWindowSize()