From 9075129df06973a64440a86c5ed0f02a3b7856b5 Mon Sep 17 00:00:00 2001
From: thefiddler <stapostol@gmail.com>
Date: Sun, 15 Jun 2014 14:30:23 +0200
Subject: [PATCH] [X11] Throw exception if GLX is not supported

You cannot create an X11/OpenGL context without the GLX extension.
OpenTK will now throw a `NotSupportedException` when this condition is
encountered.

In some cases, it may be possible to enable the EGL backend by passing
`GraphicsContextFlags.Embedded` to the `GraphicsContext` constructor.
---
 Source/OpenTK/Platform/X11/X11GLContext.cs | 28 ++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/Source/OpenTK/Platform/X11/X11GLContext.cs b/Source/OpenTK/Platform/X11/X11GLContext.cs
index ca77aebc..a600b8be 100644
--- a/Source/OpenTK/Platform/X11/X11GLContext.cs
+++ b/Source/OpenTK/Platform/X11/X11GLContext.cs
@@ -54,14 +54,34 @@ namespace OpenTK.Platform.X11
             if (window == null)
                 throw new ArgumentNullException("window");
 
+            // Do not move this lower, as almost everything requires the Display
+            // property to be correctly set.
+            Display = ((X11WindowInfo)window).Display;
+
+            // Check that GLX is supported. We cannot proceed to create
+            // an OpenGL context without the GLX extension.
+            int error_base;
+            int event_base;
+            int glx_major;
+            int glx_minor;
+            using (new XLock(Display))
+            {
+                bool supported = Glx.QueryExtension(Display, out error_base, out event_base);
+                supported &= Glx.QueryVersion(Display, out glx_major, out glx_minor);
+                if (supported)
+                {
+                    Debug.Print("[X11] GLX supported. Version is {0}.{1}", glx_major, glx_minor);
+                }
+                else
+                {
+                    throw new NotSupportedException("[X11] GLX extension is not supported.");
+                }
+            }
+
             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.
-            Display = ((X11WindowInfo)window).Display;
-            
             currentWindow = (X11WindowInfo)window;
             currentWindow.VisualInfo = SelectVisual(Mode, currentWindow);