Make System.Drawing.Common throw on Unix unless a config switch is set

src/libraries/System.Drawing.Common/Directory.Build.props

@@ -2,8 +2,7 @@
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
     <StrongNameKeyId>Open</StrongNameKeyId>
-    <IncludePlatformAttributes>true</IncludePlatformAttributes>
-    <UnsupportedOSPlatforms>browser</UnsupportedOSPlatforms>
+    <SupportedOSPlatforms>windows</SupportedOSPlatforms>
     <PackageDescription>Provides access to GDI+ graphics functionality.
 
 Commonly Used Types:

src/libraries/System.Drawing.Common/src/Resources/Strings.resx

@@ -353,6 +353,9 @@
   <data name="PlatformNotSupported_Drawing" xml:space="preserve">
     <value>System.Drawing is not supported on this platform.</value>
   </data>
+  <data name="PlatformNotSupported_Unix" xml:space="preserve">
+    <value>System.Drawing is not supported on non-Windows platforms. See https://aka.ms/systemdrawingnonwindows for more information.</value>
+  </data>
   <data name="PrintDocumentDesc" xml:space="preserve">
     <value>Defines an object that sends output to a printer.</value>
   </data>
@@ -464,4 +467,4 @@
   <data name="SystemDrawingCommon_PlatformNotSupported" xml:space="preserve">
     <value>System.Drawing.Common is not supported on this platform.</value>
   </data>
-</root>
+</root>

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -170,6 +170,8 @@
              Link="Common\Interop\Windows\User32\Interop.LOGFONT.cs" />
     <Compile Include="$(CommonPath)Interop\Windows\Gdi32\Interop.RasterOp.cs"
              Link="Common\Interop\Windows\Gdi32\Interop.RasterOp.cs" />
+    <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
+             Link="System\LocalAppContextSwitches.Common.cs" />
     <Compile Include="$(CommonPath)System\Text\ValueStringBuilder.cs"
              Link="Common\System\Text\ValueStringBuilder.cs" />
     <Compile Include="$(CommonPath)System\Obsoletions.cs"
@@ -207,7 +209,7 @@
     <Compile Include="System\Drawing\Internal\GpPathData.cs" />
     <Compile Include="System\Drawing\Internal\GPStream.cs" />
     <Compile Include="System\Drawing\Internal\SystemColorTracker.cs" />
-    <Compile Include="System\Drawing\LocalAppContextSwitches.cs" />
+    <Compile Include="System\Drawing\LocalAppContextSwitches.Windows.cs" />
     <Compile Include="System\Drawing\Pen.Windows.cs" />
     <Compile Include="System\Drawing\Printing\DefaultPrintController.cs" />
     <Compile Include="System\Drawing\Printing\ModeField.cs" />
@@ -243,8 +245,6 @@
     <Compile Include="Interop\Windows\Interop.Shell32.cs" />
     <Compile Include="Interop\Windows\Interop.User32.cs" />
     <Compile Include="Interop\Windows\Interop.Winspool.cs" />
-    <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
-             Link="System\LocalAppContextSwitches.Common.cs" />
     <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
              Link="Common\Interop\Windows\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Windows\Gdi32\Interop.CombineRgn.cs"
@@ -359,6 +359,7 @@
     <Compile Include="System\Drawing\GdiplusNative.Unix.cs" />
     <Compile Include="System\Drawing\GdiPlusStreamHelper.Unix.cs" />
     <Compile Include="System\Drawing\LibX11Functions.cs" />
+    <Compile Include="System\Drawing\LocalAppContextSwitches.Unix.cs" />
     <Compile Include="System\Drawing\MarshallingHelpers.cs" />
     <Compile Include="System\Drawing\Image.Unix.cs" />
     <Compile Include="System\Drawing\Pen.Unix.cs" />

src/libraries/System.Drawing.Common/src/System/Drawing/GdiplusNative.Unix.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Collections.Generic;
 using System.Drawing.Drawing2D;
 using System.Drawing.Imaging;
@@ -62,6 +63,9 @@ internal static IntPtr LoadNativeLibrary()
 
             private static void PlatformInitialize()
             {
+                if (!LocalAppContextSwitches.EnableUnixSupport)
+                    throw new PlatformNotSupportedException(SR.PlatformNotSupported_Unix);
+
                 LibraryResolver.EnsureRegistered();
             }
 

src/libraries/System.Drawing.Common/src/System/Drawing/LocalAppContextSwitches.Unix.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    internal static partial class LocalAppContextSwitches
+    {
+        private static int s_enableUnixSupport;
+        public static bool EnableUnixSupport
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return GetCachedSwitchValue(@"System.Drawing.EnableUnixSupport", ref s_enableUnixSupport);
+            }
+        }
+    }
+}

src/libraries/System.Drawing.Common/tests/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+    "configProperties": {
+        "System.Drawing.EnableUnixSupport": true
+    }
+}