Imported Upstream version 4.2.0.179

Former-commit-id: 4610231f55806d2a05ed69e5ff3faa7336cc1479

mcs/class/System.Windows.Forms/System.Windows.Forms.VisualStyles/VisualStylesEngine.cs

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+//
+// VisualStylesEngine.cs: Selects and provides an IVisualStyles.
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+// 
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+// Copyright (c) 2008 George Giolfan
+//
+// Authors:
+//	George Giolfan (georgegiolfan@yahoo.com)
+//
+
+namespace System.Windows.Forms.VisualStyles
+{
+	class VisualStylesEngine
+	{
+		static IVisualStyles instance = Initialize ();
+		public static IVisualStyles Instance {
+			get { return instance; }
+		}
+		static IVisualStyles Initialize ()
+		{
+			string environment_variable = Environment.GetEnvironmentVariable("MONO_VISUAL_STYLES");
+			if (environment_variable != null)
+				environment_variable = environment_variable.ToLower ();
+			if (
+#if !VISUAL_STYLES_USE_GTKPLUS_ON_WINDOWS
+				environment_variable == "gtkplus" &&
+#endif
+				VisualStylesGtkPlus.Initialize ())
+				return new VisualStylesGtkPlus ();
+			return new VisualStylesNative ();
+		}
+	}
+}