Fix GetDeviceCoordinates. In some cases PresentationSource.FromVisual(this) may return null.

Hardcodet.NotifyIcon.Wpf/Source/NotifyIconWpf/Interop/SystemInfo.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Windows.Interop;
+
+namespace Hardcodet.Wpf.TaskbarNotification.Interop
+{
+  public static class SystemInfo
+  {
+    private static Tuple<double, double> dpiFactors;
+
+    private static Tuple<double, double> DpiFactors
+    {
+      get
+      {
+        if (dpiFactors == null)        
+          using (var source = new HwndSource(new HwndSourceParameters()))
+            dpiFactors = Tuple.Create(source.CompositionTarget.TransformToDevice.M11, source.CompositionTarget.TransformToDevice.M22);        
+        return dpiFactors;
+      }
+    }
+
+    public static double DpiXFactor
+    {
+      get
+      {
+        var factors = DpiFactors;
+        return factors != null ? factors.Item1 : 1;
+      }
+    }
+
+    public static double DpiYFactor
+    {
+      get
+      {
+        var factors = DpiFactors;
+        return factors != null ? factors.Item2 : 1;
+      }
+    }         
+  }
+}