Merge branch 'master' of https://github.com/Arlorean/Perspex into dpi-aware

src/Windows/Perspex.Win32/Interop/UnmanagedMethods.cs

@@ -718,7 +718,6 @@ namespace Perspex.Win32.Interop
         [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
         public static extern IntPtr GlobalLock(IntPtr handle);
 
-
         [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
         public static extern bool GlobalUnlock(IntPtr handle);
 
@@ -737,6 +736,35 @@ namespace Perspex.Win32.Interop
         [DllImport("comdlg32.dll")]
         public static extern int CommDlgExtendedError();
 
+        [DllImport("shcore.dll")]
+        public static extern void SetProcessDpiAwareness(PROCESS_DPI_AWARENESS value);
+
+        [DllImport("shcore.dll")]
+        public static extern long GetDpiForMonitor(IntPtr hmonitor, MONITOR_DPI_TYPE dpiType, out uint dpiX, out uint dpiY);
+
+        [DllImport("shcore.dll")]
+        public static extern void GetScaleFactorForMonitor(IntPtr hMon, out uint pScale);
+
+        [DllImport("user32.dll")]
+        public static extern IntPtr MonitorFromPoint(POINT pt, uint dwFlags);
+
+        public const uint MONITOR_DEFAULTTONULL = 0x00000000;
+        public const uint MONITOR_DEFAULTTOPRIMARY = 0x00000001;
+        public const uint MONITOR_DEFAULTTONEAREST = 0x00000002;
+
+        public enum PROCESS_DPI_AWARENESS {
+            PROCESS_DPI_UNAWARE = 0,
+            PROCESS_SYSTEM_DPI_AWARE = 1,
+            PROCESS_PER_MONITOR_DPI_AWARE = 2
+        }
+
+        public enum MONITOR_DPI_TYPE {
+            MDT_EFFECTIVE_DPI = 0,
+            MDT_ANGULAR_DPI = 1,
+            MDT_RAW_DPI = 2,
+            MDT_DEFAULT = MDT_EFFECTIVE_DPI
+        } 
+
         public enum ClipboardFormat
         {
             CF_TEXT = 1,

src/Windows/Perspex.Win32/Win32Platform.cs

@@ -26,21 +26,38 @@ namespace Perspex.Win32
         private UnmanagedMethods.WndProc _wndProcDelegate;
 
         private IntPtr _hwnd;
-
+        private double scale = 1.0;
         private readonly List<Delegate> _delegates = new List<Delegate>();
 
         public Win32Platform()
         {
+            HandleDPI();
             CreateMessageWindow();
         }
 
+        private void HandleDPI() {
+            // Declare that this process is aware of per monitor DPI 
+            UnmanagedMethods.SetProcessDpiAwareness(UnmanagedMethods.PROCESS_DPI_AWARENESS.PROCESS_PER_MONITOR_DPI_AWARE);
+
+            // Get the DPI for the main monitor, and set the scaling factor
+            UnmanagedMethods.POINT pt = new UnmanagedMethods.POINT() { X = 1, Y = 1 };
+            var hMonitor = UnmanagedMethods.MonitorFromPoint(pt, UnmanagedMethods.MONITOR_DEFAULTTONEAREST);
+
+            // TODO: Check for failure
+            uint dpix, dpiy;
+            UnmanagedMethods.GetDpiForMonitor(hMonitor, UnmanagedMethods.MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI, out dpix, out dpiy);
+
+            // Set scale based on x DPI
+            scale = dpix / 100.0;
+        }
+
         public Size DoubleClickSize => new Size(
             UnmanagedMethods.GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CXDOUBLECLK),
             UnmanagedMethods.GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDOUBLECLK));
 
         public TimeSpan DoubleClickTime => TimeSpan.FromMilliseconds(UnmanagedMethods.GetDoubleClickTime());
-        public double RenderScalingFactor { get; } = 1;
-        public double LayoutScalingFactor { get; } = 1;
+        public double RenderScalingFactor { get { return scale; } }
+        public double LayoutScalingFactor { get { return scale; } }
 
         public static void Initialize()
         {