glx: use glXGetProcAddressARB to get glXCreateContextAttribsARB

This doesn't have to be exported and was found when testing with mesa without glvnd enabled.

Signed-off-by: Mary Guillemard <mary@mary.zone>

Author: marysaka

SPB.Testing/Program.cs

@@ -34,6 +34,7 @@ static void Main(string[] args)
             Console.WriteLine($"OpenGL renderer: {GL.GetString(StringName.Renderer)}");
             Console.WriteLine($"OpenGL context profile mask: {GL.GetInteger((GetPName)All.ContextProfileMask)}");
             Console.WriteLine($"OpenGL context flags: {GL.GetInteger((GetPName)All.ContextFlags)}");
+            Console.WriteLine($"Window swap interval: {window.SwapInterval}");
 
             Thread.Sleep(2000);
 

SPB/Platform/GLX/GLX.cs

@@ -204,10 +204,6 @@ public enum CreateContext : int
 
             [DllImport(LibraryName, EntryPoint = "glXGetProcAddressARB")]
             public static extern IntPtr GetProcAddress(string procName);
-
-
-            [DllImport(LibraryName, EntryPoint = "glXCreateContextAttribsARB")]
-            public static extern Context CreateContextAttribs(Display display, IntPtr fbConfigs, Context shareContext, bool direct, int[] attributes);
         }
 
         internal sealed class Ext

SPB/Platform/GLX/GLXHelper.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 using SPB.Graphics;
 using SPB.Graphics.OpenGL;
@@ -11,6 +12,30 @@ namespace SPB.Platform.GLX
     [SupportedOSPlatform("linux")]
     public sealed class GLXHelper
     {
+        private static bool _isInit = false;
+
+        [UnmanagedFunctionPointer(CallingConvention.Winapi)]
+        private delegate IntPtr glxCreateContextAttribsARBDelegate(IntPtr display, IntPtr fbConfigs, IntPtr shareContext, bool direct, int[] attributes);
+
+        private static glxCreateContextAttribsARBDelegate CreateContextAttribsArb;
+
+        private static void EnsureInit()
+        {
+            if (!_isInit)
+            {
+                CreateContextAttribsArb = Marshal.GetDelegateForFunctionPointer<glxCreateContextAttribsARBDelegate>(GLX.ARB.GetProcAddress("glXCreateContextAttribsARB"));
+
+                _isInit = true;
+            }
+        }
+
+        public static IntPtr CreateContextAttribs(IntPtr display, IntPtr fbConfigs, IntPtr shareContext, bool direct, int[] attributes)
+        {
+            EnsureInit();
+
+            return CreateContextAttribsArb(display, fbConfigs, shareContext, direct, attributes);
+        }
+
         public static List<int> FramebufferFormatToVisualAttribute(FramebufferFormat format)
         {
             List<int> result = new List<int>();

SPB/Platform/GLX/GLXOpenGLContext.cs

@@ -72,11 +72,11 @@ public override void Initialize(NativeWindowBase window = null)
 
             IntPtr shareContextHandle = ShareContext == null ? IntPtr.Zero : ShareContext.ContextHandle;
 
-            IntPtr context = GLX.ARB.CreateContextAttribs(display, fbConfig, shareContextHandle, DirectRendering, contextAttribute.ToArray());
+            IntPtr context = GLXHelper.CreateContextAttribs(display, fbConfig, shareContextHandle, DirectRendering, contextAttribute.ToArray());
 
             if (context == IntPtr.Zero)
             {
-                context = GLX.ARB.CreateContextAttribs(display, fbConfig, shareContextHandle, !DirectRendering, contextAttribute.ToArray());
+                context = GLXHelper.CreateContextAttribs(display, fbConfig, shareContextHandle, !DirectRendering, contextAttribute.ToArray());
 
                 DirectRendering = !DirectRendering;
             }