Add API to let users pick OpenGL version

src/Windowing/OpenToolkit.Windowing.Common/Enums/OpenGLVersion.cs

@@ -0,0 +1,27 @@
+//
+// OpenGLVersion.cs
+//
+// Copyright (C) 2019 OpenTK
+//
+// This software may be modified and distributed under the terms
+// of the MIT license. See the LICENSE file for details.
+//
+
+namespace OpenToolkit.Windowing.Common
+{
+    /// <summary>
+    /// Describes the OpenGL version you want the window to use.
+    /// </summary>
+    public enum OpenGLVersion
+    {
+        /// <summary>
+        /// Selects core profile OpenGL 3.3
+        /// </summary>
+        OPENGL_3_3_CORE,
+
+        /// <summary>
+        /// Selects compatability profile OpenGL 3.3
+        /// </summary>
+        OPENGL_3_3_COMPAT,
+    }
+}

src/Windowing/OpenToolkit.Windowing.Common/Interfaces/INativeWindowProperties.cs

@@ -39,6 +39,11 @@ public interface INativeWindowProperties
         /// </summary>
         Monitor CurrentMonitor { get; set; }
 
+        /// <summary>
+        /// Gets a value representing the current OpenGL version.
+        /// </summary>
+        OpenGLVersion Version { get; }
+
         /// <summary>
         /// Gets or sets the clipboard string.
         /// </summary>

src/Windowing/OpenToolkit.Windowing.Common/OpenToolkit.Windowing.Common.csproj

@@ -21,10 +21,6 @@
     <ProjectReference Include="..\..\OpenToolkit.Mathematics\OpenToolkit.Mathematics.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="Enums" />
-  </ItemGroup>
-
   <Import Project="..\..\..\props\common.props" />
   <Import Project="..\..\..\props\nuget-common.props" />
   <Import Project="..\..\..\props\stylecop.props" />

src/Windowing/OpenToolkit.Windowing.Desktop/NativeWindow.cs

@@ -108,6 +108,9 @@ public string Title
             }
         }
 
+        /// <inheritdoc />
+        public OpenGLVersion Version { get; }
+
         private Monitor _currentMonitor;
 
         /// <summary>
@@ -466,6 +469,36 @@ public NativeWindow(INativeWindowProperties settings)
                         break;
                 }
 
+                int major, minor;
+                bool isCompat;
+
+                switch (Version)
+                {
+                    case OpenGLVersion.OPENGL_3_3_CORE:
+                        major = 3;
+                        minor = 3;
+                        isCompat = false;
+                        break;
+
+                    case OpenGLVersion.OPENGL_3_3_COMPAT:
+                        major = 3;
+                        minor = 3;
+                        isCompat = true;
+                        break;
+
+                    default:
+                        throw new Exception("Could not find version requested");
+                }
+
+                Glfw.WindowHint(WindowHintInt.ContextVersionMajor, major);
+                Glfw.WindowHint(WindowHintInt.ContextVersionMinor, minor);
+
+                Glfw.WindowHint
+                (
+                    WindowHintOpenGlProfile.OpenGlProfile,
+                    isCompat ? OpenGlProfile.Compat : OpenGlProfile.Core
+                );
+
                 Glfw.WindowHint(WindowHintBool.Focused, settings.IsFocused);
                 _windowBorder = settings.WindowBorder;
 

src/Windowing/OpenToolkit.Windowing.Desktop/NativeWindowSettings.cs

@@ -52,6 +52,8 @@ public NativeWindowSettings()
             Width = 640;
             Height = 360;
 
+            Version = OpenGLVersion.OPENGL_3_3_CORE;
+
             IsFullscreen = false;
 
             Exists = true;
@@ -66,6 +68,11 @@ public NativeWindowSettings()
         /// <inheritdoc />
         public string ClipboardString { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value representing the current OpenGL version.
+        /// </summary>
+        public OpenGLVersion Version { get; set; }
+
         /// <inheritdoc />
         public Monitor CurrentMonitor { get; set; }