Implemented basic layout scaling.

Maybe works... I don't have a high DPI monitor to test on...

src/Perspex.Input/Perspex.Input.csproj

@@ -100,7 +100,6 @@
     <Compile Include="Navigation\FocusExtensions.cs" />
     <Compile Include="Navigation\DirectionalNavigation.cs" />
     <Compile Include="Navigation\TabNavigation.cs" />
-    <Compile Include="Platform\IPlatformSettings.cs" />
     <Compile Include="PointerWheelEventArgs.cs" />
     <Compile Include="Raw\RawMouseWheelEventArgs.cs" />
     <Compile Include="Raw\RawSizeEventArgs.cs" />

src/Perspex.Layout/Layoutable.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Linq;
+using Perspex.Platform;
 using Perspex.VisualTree;
 using Serilog;
 using Serilog.Core.Enrichers;
@@ -466,6 +467,7 @@ namespace Perspex.Layout
                     .Deflate(margin);
 
                 var measured = MeasureOverride(constrained);
+
                 var width = measured.Width;
                 var height = measured.Height;
 
@@ -485,6 +487,13 @@ namespace Perspex.Layout
                 height = Math.Min(height, MaxHeight);
                 height = Math.Max(height, MinHeight);
 
+                if (UseLayoutRounding)
+                {
+                    var scale = GetLayoutScale();
+                    width = Math.Ceiling(width * scale) / scale;
+                    height = Math.Ceiling(height * scale) / scale;
+                }
+
                 return NonNegative(new Size(width, height).Inflate(margin));
             }
             else
@@ -510,12 +519,6 @@ namespace Perspex.Layout
                 height = Math.Max(height, child.DesiredSize.Height);
             }
 
-            if (UseLayoutRounding)
-            {
-                width = Math.Ceiling(width);
-                height = Math.Ceiling(height);
-            }
-
             return new Size(width, height);
         }
 
@@ -537,6 +540,7 @@ namespace Perspex.Layout
                     Math.Max(0, finalRect.Width - Margin.Left - Margin.Right),
                     Math.Max(0, finalRect.Height - Margin.Top - Margin.Bottom));
                 var size = sizeMinusMargins;
+                var scale = GetLayoutScale();
 
                 if (HorizontalAlignment != HorizontalAlignment.Stretch)
                 {
@@ -553,11 +557,11 @@ namespace Perspex.Layout
                 if (UseLayoutRounding)
                 {
                     size = new Size(
-                        Math.Ceiling(size.Width), 
-                        Math.Ceiling(size.Height));
+                        Math.Ceiling(size.Width * scale) / scale, 
+                        Math.Ceiling(size.Height * scale) / scale);
                     sizeMinusMargins = new Size(
-                        Math.Ceiling(sizeMinusMargins.Width), 
-                        Math.Ceiling(sizeMinusMargins.Height));
+                        Math.Ceiling(sizeMinusMargins.Width * scale) / scale, 
+                        Math.Ceiling(sizeMinusMargins.Height * scale) / scale);
                 }
 
                 size = ArrangeOverride(size).Constrain(size);
@@ -586,8 +590,8 @@ namespace Perspex.Layout
 
                 if (UseLayoutRounding)
                 {
-                    originX = Math.Floor(originX);
-                    originY = Math.Floor(originY);
+                    originX = Math.Floor(originX * scale) / scale;
+                    originY = Math.Floor(originY * scale) / scale;
                 }
 
                 Bounds = new Rect(originX, originY, size.Width, size.Height);
@@ -666,5 +670,10 @@ namespace Perspex.Layout
         {
             return new Size(Math.Max(size.Width, 0), Math.Max(size.Height, 0));
         }
+
+        private static double GetLayoutScale()
+        {
+            return PerspexLocator.Current.GetService<IPlatformSettings>()?.LayoutScalingFactor ?? 1.0;
+        }
     }
 }

src/Perspex.SceneGraph/Perspex.SceneGraph.csproj

@@ -106,6 +106,7 @@
     <Compile Include="Media\TileBrush.cs" />
     <Compile Include="Media\ImageBush.cs" />
     <Compile Include="Media\VisualBrush.cs" />
+    <Compile Include="Platform\IPlatformSettings.cs" />
     <Compile Include="RelativePoint.cs" />
     <Compile Include="Platform\IFormattedTextImpl.cs" />
     <Compile Include="Platform\IBitmapImpl.cs" />

src/Windows/Perspex.Win32/Win32Platform.cs

@@ -188,7 +188,7 @@ namespace Perspex.Win32
             UnmanagedMethods.GetDpiForMonitor(hMonitor, UnmanagedMethods.MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI, out dpix, out dpiy);
 
             // Set scale based on x DPI
-            _scale = dpix / 100.0;
+            _scale = dpix / 96.0;
         }
     }
 }