Check for Windows version in Direct2D platform

src/Avalonia.Controls/Platform/ExportWindowingSubsystemAttribute.cs

@@ -9,16 +9,19 @@ namespace Avalonia.Platform
     [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
     public class ExportWindowingSubsystemAttribute : Attribute
     {
-        public ExportWindowingSubsystemAttribute(OperatingSystemType requiredRuntimePlatform, int priority, string name, Type initializationType, string initializationMethod)
+        public ExportWindowingSubsystemAttribute(OperatingSystemType requiredRuntimePlatform, int priority, string name, Type initializationType,
+            string initializationMethod, Type environmentChecker = null)
         {
             Name = name;
             InitializationType = initializationType;
             InitializationMethod = initializationMethod;
+            EnvironmentChecker = environmentChecker;
             RequiredOS = requiredRuntimePlatform;
             Priority = priority;
         }
 
         public string InitializationMethod { get; private set; }
+        public Type EnvironmentChecker { get; }
         public Type InitializationType { get; private set; }
         public string Name { get; private set; }
         public int Priority { get; private set; }

src/Avalonia.DotNetFrameworkRuntime/AppBuilder.cs

@@ -31,6 +31,20 @@ namespace Avalonia
             Instance = app;
         }
 
+        bool CheckEnvironment(Type checkerType)
+        {
+            if (checkerType == null)
+                return true;
+            try
+            {
+                return ((IModuleEnvironmentChecker) Activator.CreateInstance(checkerType)).IsCompatible;
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
         /// <summary>
         /// Instructs the <see cref="AppBuilder"/> to use the best settings for the platform.
         /// </summary>
@@ -43,13 +57,13 @@ namespace Avalonia
 
             var windowingSubsystemAttribute = (from assembly in RuntimePlatform.GetLoadedAssemblies()
                                                from attribute in assembly.GetCustomAttributes<ExportWindowingSubsystemAttribute>()
-                                               where attribute.RequiredOS == os
+                                               where attribute.RequiredOS == os && CheckEnvironment(attribute.EnvironmentChecker)
                                                orderby attribute.Priority ascending
                                                select attribute).First();
 
             var renderingSubsystemAttribute = (from assembly in RuntimePlatform.GetLoadedAssemblies()
                                                from attribute in assembly.GetCustomAttributes<ExportRenderingSubsystemAttribute>()
-                                               where attribute.RequiredOS == os
+                                               where attribute.RequiredOS == os && CheckEnvironment(attribute.EnvironmentChecker)
                                                where attribute.RequiresWindowingSubsystem == null
                                                 || attribute.RequiresWindowingSubsystem == windowingSubsystemAttribute.Name
                                                orderby attribute.Priority ascending

src/Avalonia.Visuals/Avalonia.Visuals.csproj

@@ -102,6 +102,7 @@
     <Compile Include="Media\Geometry.cs" />
     <Compile Include="Media\IDrawingContext.cs" />
     <Compile Include="Platform\ExportRenderingSubsystemAttribute.cs" />
+    <Compile Include="Platform\IModuleEnvironmentChecker.cs" />
     <Compile Include="Rendering\IRenderer.cs" />
     <Compile Include="Rendering\IRendererFactory.cs" />
     <Compile Include="Rendering\IRenderLoop.cs" />

src/Avalonia.Visuals/Platform/ExportRenderingSubsystemAttribute.cs

@@ -9,16 +9,19 @@ namespace Avalonia.Platform
     [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
     public class ExportRenderingSubsystemAttribute : Attribute
     {
-        public ExportRenderingSubsystemAttribute(OperatingSystemType requiredOS, int priority, string name, Type initializationType, string initializationMethod)
+        public ExportRenderingSubsystemAttribute(OperatingSystemType requiredOS, int priority, string name, Type initializationType, string initializationMethod,
+            Type environmentChecker = null)
         {
             Name = name;
             InitializationType = initializationType;
             InitializationMethod = initializationMethod;
+            EnvironmentChecker = environmentChecker;
             RequiredOS = requiredOS;
             Priority = priority;
         }
 
         public string InitializationMethod { get; private set; }
+        public Type EnvironmentChecker { get; }
         public Type InitializationType { get; private set; }
         public string Name { get; private set; }
         public int Priority { get; private set; }

src/Avalonia.Visuals/Platform/IModuleEnvironmentChecker.cs

@@ -0,0 +1,7 @@
+namespace Avalonia.Platform
+{
+    public interface IModuleEnvironmentChecker
+    {
+        bool IsCompatible { get; }
+    }
+}

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

@@ -83,6 +83,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="RenderTarget.cs" />
     <Compile Include="SwapChainRenderTarget.cs" />
+    <Compile Include="WindowsVersionChecker.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="app.config" />

src/Windows/Avalonia.Direct2D1/Properties/AssemblyInfo.cs

@@ -6,5 +6,6 @@ using Avalonia.Platform;
 using Avalonia.Direct2D1;
 
 [assembly: AssemblyTitle("Avalonia.Direct2D1")]
-[assembly: ExportRenderingSubsystem(OperatingSystemType.WinNT, 1, "Direct2D1", typeof(Direct2D1Platform), nameof(Direct2D1Platform.Initialize))]
+[assembly: ExportRenderingSubsystem(OperatingSystemType.WinNT, 1, "Direct2D1", typeof(Direct2D1Platform), nameof(Direct2D1Platform.Initialize),
+    typeof(WindowsVersionChecker))]
 

src/Windows/Avalonia.Direct2D1/WindowsVersionChecker.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Avalonia.Platform;
+
+namespace Avalonia.Direct2D1
+{
+    class WindowsVersionChecker : IModuleEnvironmentChecker
+    {
+        //Direct2D backend doesn't work with Win7 anymore
+        public bool IsCompatible => Environment.OSVersion.Version >= new Version(6, 2);
+    }
+}