Fix support for 3.2+ contexts (issue 3111)

glXGetProcAddress may return a non-null value even if a function is not
supported by the server. We need to check the extension string using
any GLX extensions. Fixes issue http://www.opentk.com/node/3111 "GLX
extension support is not checked correctly".

Furthermore, mode selection is now performed explicitly by the
X11GLContext constructor.

Source/OpenTK/Platform/X11/Bindings/Glx.cs

@@ -231,11 +231,14 @@ namespace OpenTK.Platform.X11
     {
         DebugBit = 0x0001,
         ForwardCompatibleBit = 0x0002,
+        CoreProfileBit = 0x00000001,
+        CompatibilityProfileBit = 0x00000002,
         MajorVersion = 0x2091,
         MinorVersion = 0x2092,
         LayerPlane = 0x2093,
         Flags = 0x2094,
         ErrorInvalidVersion = 0x2095,
+        ProfileMask = 0x9126
     }
 
     enum ErrorCode : int

Source/OpenTK/Platform/X11/X11Factory.cs

@@ -77,7 +77,7 @@ namespace OpenTK.Platform.X11
 
         public virtual IGraphicsMode CreateGraphicsMode()
         {
-            return new X11GraphicsMode();
+            throw new NotSupportedException();
         }
 
         public virtual OpenTK.Input.IKeyboardDriver2 CreateKeyboardDriver()

Source/OpenTK/Platform/X11/X11GLContext.cs

@@ -33,6 +33,8 @@ namespace OpenTK.Platform.X11
         int swap_interval = 1; // As defined in GLX_SGI_swap_control
         bool glx_loaded;
 
+        readonly X11GraphicsMode ModeSelector = new X11GraphicsMode();
+
         #endregion
 
         #region --- Constructors ---
@@ -45,7 +47,9 @@ namespace OpenTK.Platform.X11
             if (window == null)
                 throw new ArgumentNullException("window");
 
-            Mode = mode;
+            Mode = ModeSelector.SelectGraphicsMode(
+                mode.ColorFormat, mode.Depth, mode.Stencil, mode.Samples,
+                mode.AccumulatorFormat, mode.Buffers, mode.Stereo);
 
             // Do not move this lower, as almost everything requires the Display
             // property to be correctly set.
@@ -80,7 +84,7 @@ namespace OpenTK.Platform.X11
             // HACK: It seems that Catalyst 9.1 - 9.4 on Linux have problems with contexts created through
             // GLX_ARB_create_context, including hideous input lag, no vsync and other madness.
             // Use legacy context creation if the user doesn't request a 3.0+ context.
-            if ((major * 10 + minor >= 30) && Glx.Delegates.glXCreateContextAttribsARB != null)
+            if ((major * 10 + minor >= 30) && SupportsCreateContextAttribs(Display, currentWindow))
             {
                 Debug.Write("Using GLX_ARB_create_context... ");
                 
@@ -104,9 +108,10 @@ namespace OpenTK.Platform.X11
                         attributes.Add(minor);
                         if (flags != 0)
                         {
-#warning "This is not entirely correct: Embedded is not a valid flag! We need to add a GetARBContextFlags(GraphicsContextFlags) method."
                             attributes.Add((int)ArbCreateContext.Flags);
-                            attributes.Add((int)flags);
+                            attributes.Add((int)GetARBContextFlags(flags));
+                            attributes.Add((int)ArbCreateContext.ProfileMask);
+                            attributes.Add((int)GetARBProfileFlags(flags));
                         }
                         // According to the docs, " <attribList> specifies a list of attributes for the context.
                         // The list consists of a sequence of <name,value> pairs terminated by the
@@ -225,23 +230,46 @@ namespace OpenTK.Platform.X11
 
         #endregion
 
-        bool SupportsExtension(X11WindowInfo window, string e)
+        ArbCreateContext GetARBContextFlags(GraphicsContextFlags flags)
+        {
+            ArbCreateContext result = 0;
+            result |= (flags & GraphicsContextFlags.Debug) != 0 ? ArbCreateContext.DebugBit : 0;
+            return result;
+        }
+
+        ArbCreateContext GetARBProfileFlags(GraphicsContextFlags flags)
+        {
+            ArbCreateContext result = 0;
+            result |= (flags & GraphicsContextFlags.ForwardCompatible) != 0 ?
+                ArbCreateContext.ForwardCompatibleBit : ArbCreateContext.CompatibilityProfileBit;
+            return result;
+        }
+
+        static bool SupportsExtension(IntPtr display, X11WindowInfo window, string e)
         {
             if (window == null)
                 throw new ArgumentNullException("window");
             if (e == null)
                 throw new ArgumentNullException("e");
-            if (window.Display != Display)
+            if (window.Display != display)
                 throw new InvalidOperationException();
 
             string extensions = null;
-            using (new XLock(Display))
+            using (new XLock(display))
             {
-                extensions = Glx.QueryExtensionsString(Display, window.Screen);
+                extensions = Glx.QueryExtensionsString(display, window.Screen);
             }
             return !String.IsNullOrEmpty(extensions) && extensions.Contains(e);
         }
 
+        static bool SupportsCreateContextAttribs(IntPtr display, X11WindowInfo window)
+        {
+            return
+                SupportsExtension(display, window, "GLX_ARB_create_context") &&
+                SupportsExtension(display, window, "GLX_ARB_create_context_profile") &&
+                Glx.Delegates.glXCreateContextAttribsARB != null;
+        }
+
         #endregion
 
         #region --- IGraphicsContext Members ---