Fix EntryPointNotFound on Windows 8 due to missing version check (#6471)

* Prevent calls to unavailable entrypoint 'GetDpiForMonitor' on Win8 (#5357)

* Introduce Windows8 platform constant

* wip

Co-authored-by: Tim Schneeberger <tim.schneeberger@outlook.de>
Co-authored-by: Tim Schneeberger <thebone.main@gmail.com>
Co-authored-by: Dan Walmsley <dan@walms.co.uk>

src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj

@@ -12,6 +12,7 @@
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\packages\Avalonia\Avalonia.csproj" />
+    <ProjectReference Include="..\Avalonia.Win32\Avalonia.Win32.csproj" />
   </ItemGroup>
   <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\SharpDX.props" />

src/Windows/Avalonia.Direct2D1/HwndRenderTarget.cs

@@ -1,4 +1,5 @@
 using Avalonia.Platform;
+using Avalonia.Win32;
 using Avalonia.Win32.Interop;
 using SharpDX;
 using SharpDX.DXGI;
@@ -21,7 +22,7 @@ namespace Avalonia.Direct2D1
 
         protected override Size2F GetWindowDpi()
         {
-            if (UnmanagedMethods.ShCoreAvailable)
+            if (UnmanagedMethods.ShCoreAvailable && Win32Platform.WindowsVersion > PlatformConstants.Windows8)
             {
                 uint dpix, dpiy;
 

src/Windows/Avalonia.Win32/FramebufferManager.cs

@@ -87,7 +87,7 @@ namespace Avalonia.Win32
 
         private Vector GetCurrentDpi()
         {
-            if (UnmanagedMethods.ShCoreAvailable)
+            if (UnmanagedMethods.ShCoreAvailable && Win32Platform.WindowsVersion > PlatformConstants.Windows8)
             {
                 var monitor =
                     UnmanagedMethods.MonitorFromWindow(_hwnd, UnmanagedMethods.MONITOR.MONITOR_DEFAULTTONEAREST);

src/Windows/Avalonia.Win32/PlatformConstants.cs

@@ -1,8 +1,13 @@
+using System;
+
 namespace Avalonia.Win32
 {
-    static class PlatformConstants
+    public static class PlatformConstants
     {
         public const string WindowHandleType = "HWND";
         public const string CursorHandleType = "HCURSOR";
+
+        public static readonly Version Windows8 = new Version(6, 2);
+        public static readonly Version Windows7 = new Version(6, 1);
     }
 }

src/Windows/Avalonia.Win32/Win32GlManager.cs

@@ -1,4 +1,3 @@
-using System;
 using Avalonia.OpenGL;
 using Avalonia.OpenGL.Angle;
 using Avalonia.OpenGL.Egl;
@@ -9,7 +8,6 @@ namespace Avalonia.Win32
 {
     static class Win32GlManager
     {
-        private static readonly Version Windows7 = new Version(6, 1);
 
         public static void Initialize()
         {
@@ -22,7 +20,7 @@ namespace Avalonia.Win32
                     return wgl;
                 }
 
-                if (opts?.AllowEglInitialization ?? Win32Platform.WindowsVersion > Windows7)
+                if (opts?.AllowEglInitialization ?? Win32Platform.WindowsVersion > PlatformConstants.Windows7)
                 {
                     var egl = EglPlatformOpenGlInterface.TryCreate(() => new AngleWin32EglDisplay());
 

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -94,7 +94,7 @@ namespace Avalonia
 
 namespace Avalonia.Win32
 {
-    class Win32Platform : IPlatformThreadingInterface, IPlatformSettings, IWindowingPlatform, IPlatformIconLoader, IPlatformLifetimeEventsImpl
+    public class Win32Platform : IPlatformThreadingInterface, IPlatformSettings, IWindowingPlatform, IPlatformIconLoader, IPlatformLifetimeEventsImpl
     {
         private static readonly Win32Platform s_instance = new Win32Platform();
         private static Thread _uiThread;

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -764,8 +764,8 @@ namespace Avalonia.Win32
                 RegisterTouchWindow(_hwnd, 0);
             }
 
-            if (ShCoreAvailable)
-            {
+            if (ShCoreAvailable && Win32Platform.WindowsVersion > PlatformConstants.Windows8)
+			{
                 var monitor = MonitorFromWindow(
                     _hwnd,
                     MONITOR.MONITOR_DEFAULTTONEAREST);