Use different implementations for accessing GDI+ internals on .Net and Mono.

Source/OpenTK/GdiPlus.cs

@@ -18,6 +18,8 @@ namespace OpenTK.Platform
 {
     internal static class GdiPlus
     {
+        static IGdiPlusInternals internals;
+
         const string gdi_plus_library = "gdiplus.dll";
         static readonly PropertyInfo native_graphics_property, native_font_property;
         static readonly FieldInfo native_string_format_field;
@@ -26,33 +28,29 @@ namespace OpenTK.Platform
 
         static GdiPlus()
         {
-            native_graphics_property =
+            if (Configuration.RunningOnWindows)
-                typeof(System.Drawing.Graphics).GetProperty("NativeGraphics", BindingFlags.Instance | BindingFlags.NonPublic);
+                internals = new Windows.WinGdiPlusInternals();
-
+           else
-            native_font_property =
+                internals = new X11.X11GdiPlusInternals();
-                typeof(System.Drawing.Font).GetProperty("NativeFont", BindingFlags.Instance | BindingFlags.NonPublic);
-
-            native_string_format_field =
-                typeof(System.Drawing.StringFormat).GetField("nativeFormat", BindingFlags.Instance | BindingFlags.NonPublic);
         }
 
         #endregion
 
-        #region --- Reflection ---
+        #region --- Public Methods ---
 
         public static IntPtr GetNativeGraphics(System.Drawing.Graphics graphics)
         {
-            return (IntPtr)native_graphics_property.GetValue(graphics, null);
+            return internals.GetNativeGraphics(graphics);
         }
 
         public static IntPtr GetNativeFont(Font font)
         {
-            return (IntPtr)native_font_property.GetValue(font, null);
+            return internals.GetNativeFont(font);
         }
 
         public static IntPtr GetNativeStringFormat(StringFormat format)
         {
-            return (IntPtr)native_string_format_field.GetValue(format);
+            return internals.GetNativeStringFormat(format);
         }
 
         public static int MaxMeasurableCharacterRanges
@@ -63,11 +61,7 @@ namespace OpenTK.Platform
             }
         }
 
-        #endregion
+        [DllImport(gdi_plus_library, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true, EntryPoint = "GdipSetStringFormatMeasurableCharacterRanges")]
-
-        #region --- Methods ---
-
-        [DllImport(gdi_plus_library, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true, EntryPoint="GdipSetStringFormatMeasurableCharacterRanges")]
         public static extern int SetStringFormatMeasurableCharacterRanges(HandleRef format, int rangeCount, [In, Out] CharacterRange[] range);
 
         [DllImport(gdi_plus_library, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true, EntryPoint = "GdipGetStringFormatMeasurableCharacterRangeCount")]
@@ -87,6 +81,7 @@ namespace OpenTK.Platform
 
         #endregion
 
+#if false
         [StructLayout(LayoutKind.Sequential)]
         internal struct GPRECTF
         {
@@ -122,9 +117,6 @@ namespace OpenTK.Platform
                 return new RectangleF(this.X, this.Y, this.Width, this.Height);
             }
         }
-
+#endif
-
     }
-
-
 }

Source/OpenTK/Platform/IGdiPlusInternals.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenTK.Platform
+{
+    // Provides methods to access internal GdiPlus fields. This is necessary for
+    // managed <-> native GdiPlus interoperability.
+    // Note that the fields are named differently between .Net and Mono.
+    // GdiPlus is considered deprecated by Microsoft - it is highly unlikely that
+    // future framework upgrades will break this code, but it is something to
+    // keep in mind.
+    interface IGdiPlusInternals
+    {
+        IntPtr GetNativeGraphics(System.Drawing.Graphics graphics);
+
+        IntPtr GetNativeFont(System.Drawing.Font font);
+
+        IntPtr GetNativeStringFormat(System.Drawing.StringFormat format);
+    }
+}

Source/OpenTK/Platform/Windows/WinGdiPlusInternals.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Drawing;
+using System.Reflection;
+
+namespace OpenTK.Platform.Windows
+{
+    class WinGdiPlusInternals : IGdiPlusInternals
+    {
+        const string gdi_plus_library = "gdiplus.dll";
+        static readonly PropertyInfo native_graphics_property, native_font_property;
+        static readonly FieldInfo native_string_format_field;
+
+        static WinGdiPlusInternals()
+        {
+            native_graphics_property =
+                typeof(System.Drawing.Graphics).GetProperty("NativeGraphics", BindingFlags.Instance | BindingFlags.NonPublic);
+
+            native_font_property =
+                typeof(System.Drawing.Font).GetProperty("NativeFont", BindingFlags.Instance | BindingFlags.NonPublic);
+
+            native_string_format_field =
+                typeof(System.Drawing.StringFormat).GetField("nativeFormat", BindingFlags.Instance | BindingFlags.NonPublic);
+        }
+
+        #region --- IGdiPlusInternals Members ---
+
+        public IntPtr GetNativeGraphics(System.Drawing.Graphics graphics)
+        {
+            return (IntPtr)native_graphics_property.GetValue(graphics, null);
+        }
+
+        public IntPtr GetNativeFont(Font font)
+        {
+            return (IntPtr)native_font_property.GetValue(font, null);
+        }
+
+        public IntPtr GetNativeStringFormat(StringFormat format)
+        {
+            return (IntPtr)native_string_format_field.GetValue(format);
+        }
+
+        #endregion
+    }
+}

Source/OpenTK/Platform/X11/X11GdiPlusInternals.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenTK.Platform.X11
+{
+    class X11GdiPlusInternals : IGdiPlusInternals
+    {
+        #region IGdiPlusInternals Members
+
+        public IntPtr GetNativeGraphics(System.Drawing.Graphics graphics)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IntPtr GetNativeFont(System.Drawing.Font font)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IntPtr GetNativeStringFormat(System.Drawing.StringFormat format)
+        {
+            throw new NotImplementedException();
+        }
+
+        #endregion
+    }
+}