text: //========================================================================
  // GLFW 3.4 GLX - www.glfw.org
  //------------------------------------------------------------------------
  // Copyright (c) 2002-2006 Marcus Geelnard
  // Copyright (c) 2006-2019 Camilla Löwy <elmindreda@glfw.org>
  //
  // This software is provided 'as-is', without any express or implied
  // warranty. In no event will the authors be held liable for any damages
  // arising from the use of this software.
  //
  // Permission is granted to anyone to use this software for any purpose,
  // including commercial applications, and to alter it and redistribute it
  // freely, subject to the following restrictions:
  //
  // 1. The origin of this software must not be misrepresented; you must not
  //    claim that you wrote the original software. If you use this software
  //    in a product, an acknowledgment in the product documentation would
  //    be appreciated but is not required.
  //
  // 2. Altered source versions must be plainly marked as such, and must not
  //    be misrepresented as being the original software.
  //
  // 3. This notice may not be removed or altered from any source
  //    distribution.
  //
  //========================================================================
  // It is fine to use C99 in this file because it will not be built with VS
  //========================================================================
  
  #include "internal.h"
  
  #include <string.h>
  #include <stdlib.h>
  #include <assert.h>
  
  #ifndef GLXBadProfileARB
   #define GLXBadProfileARB 13
  #endif
  
  
  // Returns the specified attribute of the specified GLXFBConfig
  //
  static int getGLXFBConfigAttrib(GLXFBConfig fbconfig, int attrib)
  {
      int value;
      glXGetFBConfigAttrib(_glfw.x11.display, fbconfig, attrib, &value);
      return value;
  }
  
  // Return the GLXFBConfig most closely matching the specified hints
  //
  static GLFWbool chooseGLXFBConfig(const _GLFWfbconfig* desired,
                                    GLXFBConfig* result)
  {
      GLXFBConfig* nativeConfigs;
      _GLFWfbconfig* usableConfigs;
      const _GLFWfbconfig* closest;
      int nativeCount, usableCount;
      const char* vendor;
      GLFWbool trustWindowBit = GLFW_TRUE;
  
      // HACK: This is a (hopefully temporary) workaround for Chromium
      //       (VirtualBox GL) not setting the window bit on any GLXFBConfigs
      vendor = glXGetClientString(_glfw.x11.display, GLX_VENDOR);
      if (vendor && strcmp(vendor, "Chromium") == 0)
          trustWindowBit = GLFW_FALSE;
  
      nativeConfigs =
          glXGetFBConfigs(_glfw.x11.display, _glfw.x11.screen, &nativeCount);
      if (!nativeConfigs || !nativeCount)
      {
          _glfwInputError(GLFW_API_UNAVAILABLE, "GLX: No GLXFBConfigs returned");
          return GLFW_FALSE;
      }
  
      usableConfigs = _glfw_calloc(nativeCount, sizeof(_GLFWfbconfig));
      usableCount = 0;
  
      for (int i = 0;  i < nativeCount;  i++)
      {
          const GLXFBConfig n = nativeConfigs[i];
          _GLFWfbconfig* u = usableConfigs + usableCount;
  
          // Only consider RGBA GLXFBConfigs
          if (!(getGLXFBConfigAttrib(n, GLX_RENDER_TYPE) & GLX_RGBA_BIT))
              continue;
  
          // Only consider window GLXFBConfigs
          if (!(getGLXFBConfigAttrib(n, GLX_DRAWABLE_TYPE) & GLX_WINDOW_BIT))
          {
              if (trustWindowBit)
                  continue;
          }
  
          if (getGLXFBConfigAttrib(n, GLX_DOUBLEBUFFER) != desired->doublebuffer)
              continue;
  
          if (desired->transparent)
          {
              XVisualInfo* vi = glXGetVisualFromFBConfig(_glfw.x11.display, n);
              if (vi)
              {
                  u->transparent = _glfwIsVisualTransparentX11(vi->visual);
                  XFree(vi);
              }
          }
  
          u->redBits = getGLXFBConfigAttrib(n, GLX_RED_SIZE);
          u->greenBits = getGLXFBConfigAttrib(n, GLX_GREEN_SIZE);
          u->blueBits = getGLXFBConfigAttrib(n, GLX_BLUE_SIZE);
  
          u->alphaBits = getGLXFBConfigAttrib(n, GLX_ALPHA_SIZE);
          u->depthBits = getGLXFBConfigAttrib(n, GLX_DEPTH_SIZE);
          u->stencilBits = getGLXFBConfigAttrib(n, GLX_STENCIL_SIZE);
  
          u->accumRedBits = getGLXFBConfigAttrib(n, GLX_ACCUM_RED_SIZE);
          u->accumGreenBits = getGLXFBConfigAttrib(n, GLX_ACCUM_GREEN_SIZE);
          u->accumBlueBits = getGLXFBConfigAttrib(n, GLX_ACCUM_BLUE_SIZE);
          u->accumAlphaBits = getGLXFBConfigAttrib(n, GLX_ACCUM_ALPHA_SIZE);
  
          u->auxBuffers = getGLXFBConfigAttrib(n, GLX_AUX_BUFFERS);
  
          if (getGLXFBConfigAttrib(n, GLX_STEREO))
              u->stereo = GLFW_TRUE;
  
          if (_glfw.glx.ARB_multisample)
              u->samples = getGLXFBConfigAttrib(n, GLX_SAMPLES);
  
          if (_glfw.glx.ARB_framebuffer_sRGB || _glfw.glx.EXT_framebuffer_sRGB)
              u->sRGB = getGLXFBConfigAttrib(n, GLX_FRAMEBUFFER_SRGB_CAPABLE_ARB);
  
          u->handle = (uintptr_t) n;
          usableCount++;
      }
  
      closest = _glfwChooseFBConfig(desired, usableConfigs, usableCount);
      if (closest)
          *result = (GLXFBConfig) closest->handle;
  
      XFree(nativeConfigs);
      _glfw_free(usableConfigs);
  
      return closest != NULL;
  }
  
  // Create the OpenGL context using legacy API
  //
  static GLXContext createLegacyContextGLX(_GLFWwindow* window,
                                           GLXFBConfig fbconfig,
                                           GLXContext share)
  {
      return glXCreateNewContext(_glfw.x11.display,
                                 fbconfig,
                                 GLX_RGBA_TYPE,
                                 share,
                                 True);
  }
  
  static void makeContextCurrentGLX(_GLFWwindow* window)
  {
      if (window)
      {
          if (!glXMakeCurrent(_glfw.x11.display,
                              window->context.glx.window,
                              window->context.glx.handle))
          {
              _glfwInputError(GLFW_PLATFORM_ERROR,
                              "GLX: Failed to make context current");
              return;
          }
      }
      else
      {
          if (!glXMakeCurrent(_glfw.x11.display, None, NULL))
          {
              _glfwInputError(GLFW_PLATFORM_ERROR,
                              "GLX: Failed to clear current context");
              return;
          }
      }
  
      _glfwPlatformSetTls(&_glfw.contextSlot, window);
  }
  
  static void swapBuffersGLX(_GLFWwindow* window)
  {
      glXSwapBuffers(_glfw.x11.display, window->context.glx.window);
  }
  
  static void swapIntervalGLX(int interval)
  {
      _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
  
      if (_glfw.glx.EXT_swap_control)
      {
          _glfw.glx.SwapIntervalEXT(_glfw.x11.display,
                                    window->context.glx.window,
                                    interval);
      }
      else if (_glfw.glx.MESA_swap_control)
          _glfw.glx.SwapIntervalMESA(interval);
      else if (_glfw.glx.SGI_swap_control)
      {
          if (interval > 0)
              _glfw.glx.SwapIntervalSGI(interval);
      }
  }
  
  static int extensionSupportedGLX(const char* extension)
  {
      const char* extensions =
          glXQueryExtensionsString(_glfw.x11.display, _glfw.x11.screen);
      if (extensions)
      {
          if (_glfwStringInExtensionString(extension, extensions))
              return GLFW_TRUE;
      }
  
      return GLFW_FALSE;
  }
  
  static GLFWglproc getProcAddressGLX(const char* procname)
  {
      if (_glfw.glx.GetProcAddress)
          return _glfw.glx.GetProcAddress((const GLubyte*) procname);
      else if (_glfw.glx.GetProcAddressARB)
          return _glfw.glx.GetProcAddressARB((const GLubyte*) procname);
      else
          return _glfwPlatformGetModuleSymbol(_glfw.glx.handle, procname);
  }
  
  static void destroyContextGLX(_GLFWwindow* window)
  {
      if (window->context.glx.window)
      {
          glXDestroyWindow(_glfw.x11.display, window->context.glx.window);
          window->context.glx.window = None;
      }
  
      if (window->context.glx.handle)
      {
          glXDestroyContext(_glfw.x11.display, window->context.glx.handle);
          window->context.glx.handle = NULL;
      }
  }
  
  
  //////////////////////////////////////////////////////////////////////////
  //////                       GLFW internal API                      //////
  //////////////////////////////////////////////////////////////////////////
  
  // Initialize GLX
  //
  GLFWbool _glfwInitGLX(void)
  {
      const char* sonames[] =
      {
  #if defined(_GLFW_GLX_LIBRARY)
          _GLFW_GLX_LIBRARY,
  #elif defined(__CYGWIN__)
          "libGL-1.so",
  #else
          "libGL.so.1",
          "libGL.so",
  #endif
          NULL
      };
  
      if (_glfw.glx.handle)
          return GLFW_TRUE;
  
      for (int i = 0;  sonames[i];  i++)
      {
          _glfw.glx.handle = _glfwPlatformLoadModule(sonames[i]);
          if (_glfw.glx.handle)
              break;
      }
  
      if (!_glfw.glx.handle)
      {
          _glfwInputError(GLFW_API_UNAVAILABLE, "GLX: Failed to load GLX");
          return GLFW_FALSE;
      }
  
      _glfw.glx.GetFBConfigs = (PFNGLXGETFBCONFIGSPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetFBConfigs");
      _glfw.glx.GetFBConfigAttrib = (PFNGLXGETFBCONFIGATTRIBPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetFBConfigAttrib");
      _glfw.glx.GetClientString = (PFNGLXGETCLIENTSTRINGPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetClientString");
      _glfw.glx.QueryExtension = (PFNGLXQUERYEXTENSIONPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXQueryExtension");
      _glfw.glx.QueryVersion = (PFNGLXQUERYVERSIONPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXQueryVersion");
      _glfw.glx.DestroyContext = (PFNGLXDESTROYCONTEXTPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXDestroyContext");
      _glfw.glx.MakeCurrent = (PFNGLXMAKECURRENTPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXMakeCurrent");
      _glfw.glx.SwapBuffers = (PFNGLXSWAPBUFFERSPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXSwapBuffers");
      _glfw.glx.QueryExtensionsString = (PFNGLXQUERYEXTENSIONSSTRINGPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXQueryExtensionsString");
      _glfw.glx.CreateNewContext = (PFNGLXCREATENEWCONTEXTPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXCreateNewContext");
      _glfw.glx.CreateWindow = (PFNGLXCREATEWINDOWPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXCreateWindow");
      _glfw.glx.DestroyWindow = (PFNGLXDESTROYWINDOWPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXDestroyWindow");
      _glfw.glx.GetProcAddress = (PFNGLXGETPROCADDRESSPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetProcAddress");
      _glfw.glx.GetProcAddressARB = (PFNGLXGETPROCADDRESSPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetProcAddressARB");
      _glfw.glx.GetVisualFromFBConfig = (PFNGLXGETVISUALFROMFBCONFIGPROC)
          _glfwPlatformGetModuleSymbol(_glfw.glx.handle, "glXGetVisualFromFBConfig");
  
      if (!_glfw.glx.GetFBConfigs ||
          !_glfw.glx.GetFBConfigAttrib ||
          !_glfw.glx.GetClientString ||
          !_glfw.glx.QueryExtension ||
          !_glfw.glx.QueryVersion ||
          !_glfw.glx.DestroyContext ||
          !_glfw.glx.MakeCurrent ||
          !_glfw.glx.SwapBuffers ||
          !_glfw.glx.QueryExtensionsString ||
          !_glfw.glx.CreateNewContext ||
          !_glfw.glx.CreateWindow ||
          !_glfw.glx.DestroyWindow ||
          !_glfw.glx.GetProcAddress ||
          !_glfw.glx.GetProcAddressARB ||
          !_glfw.glx.GetVisualFromFBConfig)
      {
          _glfwInputError(GLFW_PLATFORM_ERROR,
                          "GLX: Failed to load required entry points");
          return GLFW_FALSE;
      }
  
      if (!glXQueryExtension(_glfw.x11.display,
                             &_glfw.glx.errorBase,
                             &_glfw.glx.eventBase))
      {
          _glfwInputError(GLFW_API_UNAVAILABLE, "GLX: GLX extension not found");
          return GLFW_FALSE;
      }
  
      if (!glXQueryVersion(_glfw.x11.display, &_glfw.glx.major, &_glfw.glx.minor))
      {
          _glfwInputError(GLFW_API_UNAVAILABLE,
                          "GLX: Failed to query GLX version");
          return GLFW_FALSE;
      }
  
      if (_glfw.glx.major == 1 && _glfw.glx.minor < 3)
      {
          _glfwInputError(GLFW_API_UNAVAILABLE,
                          "GLX: GLX version 1.3 is required");
          return GLFW_FALSE;
      }
  
      if (extensionSupportedGLX("GLX_EXT_swap_control"))
      {
          _glfw.glx.SwapIntervalEXT = (PFNGLXSWAPINTERVALEXTPROC)
              getProcAddressGLX("glXSwapIntervalEXT");
  
          if (_glfw.glx.SwapIntervalEXT)
              _glfw.glx.EXT_swap_control = GLFW_TRUE;
      }
  
      if (extensionSupportedGLX("GLX_SGI_swap_control"))
      {
          _glfw.glx.SwapIntervalSGI = (PFNGLXSWAPINTERVALSGIPROC)
              getProcAddressGLX("glXSwapIntervalSGI");
  
          if (_glfw.glx.SwapIntervalSGI)
              _glfw.glx.SGI_swap_control = GLFW_TRUE;
      }
  
      if (extensionSupportedGLX("GLX_MESA_swap_control"))
      {
          _glfw.glx.SwapIntervalMESA = (PFNGLXSWAPINTERVALMESAPROC)
              getProcAddressGLX("glXSwapIntervalMESA");
  
          if (_glfw.glx.SwapIntervalMESA)
              _glfw.glx.MESA_swap_control = GLFW_TRUE;
      }
  
      if (extensionSupportedGLX("GLX_ARB_multisample"))
          _glfw.glx.ARB_multisample = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_ARB_framebuffer_sRGB"))
          _glfw.glx.ARB_framebuffer_sRGB = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_EXT_framebuffer_sRGB"))
          _glfw.glx.EXT_framebuffer_sRGB = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_ARB_create_context"))
      {
          _glfw.glx.CreateContextAttribsARB = (PFNGLXCREATECONTEXTATTRIBSARBPROC)
              getProcAddressGLX("glXCreateContextAttribsARB");
  
          if (_glfw.glx.CreateContextAttribsARB)
              _glfw.glx.ARB_create_context = GLFW_TRUE;
      }
  
      if (extensionSupportedGLX("GLX_ARB_create_context_robustness"))
          _glfw.glx.ARB_create_context_robustness = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_ARB_create_context_profile"))
          _glfw.glx.ARB_create_context_profile = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_EXT_create_context_es2_profile"))
          _glfw.glx.EXT_create_context_es2_profile = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_ARB_create_context_no_error"))
          _glfw.glx.ARB_create_context_no_error = GLFW_TRUE;
  
      if (extensionSupportedGLX("GLX_ARB_context_flush_control"))
          _glfw.glx.ARB_context_flush_control = GLFW_TRUE;
  
      return GLFW_TRUE;
  }
  
  // Terminate GLX
  //
  void _glfwTerminateGLX(void)
  {
      // NOTE: This function must not call any X11 functions, as it is called
      //       after XCloseDisplay (see _glfwTerminateX11 for details)
  
      if (_glfw.glx.handle)
      {
          _glfwPlatformFreeModule(_glfw.glx.handle);
          _glfw.glx.handle = NULL;
      }
  }
  
  #define setAttrib(a, v) \
  { \
      assert(((size_t) index + 1) < sizeof(attribs) / sizeof(attribs[0])); \
      attribs[index++] = a; \
      attribs[index++] = v; \
  }
  
  // Create the OpenGL or OpenGL ES context
  //
  GLFWbool _glfwCreateContextGLX(_GLFWwindow* window,
                                 const _GLFWctxconfig* ctxconfig,
                                 const _GLFWfbconfig* fbconfig)
  {
      int attribs[40];
      GLXFBConfig native = NULL;
      GLXContext share = NULL;
  
      if (ctxconfig->share)
          share = ctxconfig->share->context.glx.handle;
  
      if (!chooseGLXFBConfig(fbconfig, &native))
      {
          _glfwInputError(GLFW_FORMAT_UNAVAILABLE,
                          "GLX: Failed to find a suitable GLXFBConfig");
          return GLFW_FALSE;
      }
  
      if (ctxconfig->client == GLFW_OPENGL_ES_API)
      {
          if (!_glfw.glx.ARB_create_context ||
              !_glfw.glx.ARB_create_context_profile ||
              !_glfw.glx.EXT_create_context_es2_profile)
          {
              _glfwInputError(GLFW_API_UNAVAILABLE,
                              "GLX: OpenGL ES requested but GLX_EXT_create_context_es2_profile is unavailable");
              return GLFW_FALSE;
          }
      }
  
      if (ctxconfig->forward)
      {
          if (!_glfw.glx.ARB_create_context)
          {
              _glfwInputError(GLFW_VERSION_UNAVAILABLE,
                              "GLX: Forward compatibility requested but GLX_ARB_create_context_profile is unavailable");
              return GLFW_FALSE;
          }
      }
  
      if (ctxconfig->profile)
      {
          if (!_glfw.glx.ARB_create_context ||
              !_glfw.glx.ARB_create_context_profile)
          {
              _glfwInputError(GLFW_VERSION_UNAVAILABLE,
                              "GLX: An OpenGL profile requested but GLX_ARB_create_context_profile is unavailable");
              return GLFW_FALSE;
          }
      }
  
      _glfwGrabErrorHandlerX11();
  
      if (_glfw.glx.ARB_create_context)
      {
          int index = 0, mask = 0, flags = 0;
  
          if (ctxconfig->client == GLFW_OPENGL_API)
          {
              if (ctxconfig->forward)
                  flags |= GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB;
  
              if (ctxconfig->profile == GLFW_OPENGL_CORE_PROFILE)
                  mask |= GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
              else if (ctxconfig->profile == GLFW_OPENGL_COMPAT_PROFILE)
                  mask |= GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;
          }
          else
              mask |= GLX_CONTEXT_ES2_PROFILE_BIT_EXT;
  
          if (ctxconfig->debug)
              flags |= GLX_CONTEXT_DEBUG_BIT_ARB;
  
          if (ctxconfig->robustness)
          {
              if (_glfw.glx.ARB_create_context_robustness)
              {
                  if (ctxconfig->robustness == GLFW_NO_RESET_NOTIFICATION)
                  {
                      setAttrib(GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB,
                                GLX_NO_RESET_NOTIFICATION_ARB);
                  }
                  else if (ctxconfig->robustness == GLFW_LOSE_CONTEXT_ON_RESET)
                  {
                      setAttrib(GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB,
                                GLX_LOSE_CONTEXT_ON_RESET_ARB);
                  }
  
                  flags |= GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB;
              }
          }
  
          if (ctxconfig->release)
          {
              if (_glfw.glx.ARB_context_flush_control)
              {
                  if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_NONE)
                  {
                      setAttrib(GLX_CONTEXT_RELEASE_BEHAVIOR_ARB,
                                GLX_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB);
                  }
                  else if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_FLUSH)
                  {
                      setAttrib(GLX_CONTEXT_RELEASE_BEHAVIOR_ARB,
                                GLX_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB);
                  }
              }
          }
  
          if (ctxconfig->noerror)
          {
              if (_glfw.glx.ARB_create_context_no_error)
                  setAttrib(GLX_CONTEXT_OPENGL_NO_ERROR_ARB, GLFW_TRUE);
          }
  
          // NOTE: Only request an explicitly versioned context when necessary, as
          //       explicitly requesting version 1.0 does not always return the
          //       highest version supported by the driver
          if (ctxconfig->major != 1 || ctxconfig->minor != 0)
          {
              setAttrib(GLX_CONTEXT_MAJOR_VERSION_ARB, ctxconfig->major);
              setAttrib(GLX_CONTEXT_MINOR_VERSION_ARB, ctxconfig->minor);
          }
  
          if (mask)
              setAttrib(GLX_CONTEXT_PROFILE_MASK_ARB, mask);
  
          if (flags)
              setAttrib(GLX_CONTEXT_FLAGS_ARB, flags);
  
          setAttrib(None, None);
  
          window->context.glx.handle =
              _glfw.glx.CreateContextAttribsARB(_glfw.x11.display,
                                                native,
                                                share,
                                                True,
                                                attribs);
  
          // HACK: This is a fallback for broken versions of the Mesa
          //       implementation of GLX_ARB_create_context_profile that fail
          //       default 1.0 context creation with a GLXBadProfileARB error in
          //       violation of the extension spec
          if (!window->context.glx.handle)
          {
              if (_glfw.x11.errorCode == _glfw.glx.errorBase + GLXBadProfileARB &&
                  ctxconfig->client == GLFW_OPENGL_API &&
                  ctxconfig->profile == GLFW_OPENGL_ANY_PROFILE &&
                  ctxconfig->forward == GLFW_FALSE)
              {
                  window->context.glx.handle =
                      createLegacyContextGLX(window, native, share);
              }
          }
      }
      else
      {
          window->context.glx.handle =
              createLegacyContextGLX(window, native, share);
      }
  
      _glfwReleaseErrorHandlerX11();
  
      if (!window->context.glx.handle)
      {
          _glfwInputErrorX11(GLFW_VERSION_UNAVAILABLE, "GLX: Failed to create context");
          return GLFW_FALSE;
      }
  
      window->context.glx.window =
          glXCreateWindow(_glfw.x11.display, native, window->x11.handle, NULL);
      if (!window->context.glx.window)
      {
          _glfwInputError(GLFW_PLATFORM_ERROR, "GLX: Failed to create window");
          return GLFW_FALSE;
      }
  
      window->context.makeCurrent = makeContextCurrentGLX;
      window->context.swapBuffers = swapBuffersGLX;
      window->context.swapInterval = swapIntervalGLX;
      window->context.extensionSupported = extensionSupportedGLX;
      window->context.getProcAddress = getProcAddressGLX;
      window->context.destroy = destroyContextGLX;
  
      return GLFW_TRUE;
  }
  
  #undef setAttrib
  
  // Returns the Visual and depth of the chosen GLXFBConfig
  //
  GLFWbool _glfwChooseVisualGLX(const _GLFWwndconfig* wndconfig,
                                const _GLFWctxconfig* ctxconfig,
                                const _GLFWfbconfig* fbconfig,
                                Visual** visual, int* depth)
  {
      GLXFBConfig native;
      XVisualInfo* result;
  
      if (!chooseGLXFBConfig(fbconfig, &native))
      {
          _glfwInputError(GLFW_FORMAT_UNAVAILABLE,
                          "GLX: Failed to find a suitable GLXFBConfig");
          return GLFW_FALSE;
      }
  
      result = glXGetVisualFromFBConfig(_glfw.x11.display, native);
      if (!result)
      {
          _glfwInputError(GLFW_PLATFORM_ERROR,
                          "GLX: Failed to retrieve Visual for GLXFBConfig");
          return GLFW_FALSE;
      }
  
      *visual = result->visual;
      *depth  = result->depth;
  
      XFree(result);
      return GLFW_TRUE;
  }
  
  
  //////////////////////////////////////////////////////////////////////////
  //////                        GLFW native API                       //////
  //////////////////////////////////////////////////////////////////////////
  
  GLFWAPI GLXContext glfwGetGLXContext(GLFWwindow* handle)
  {
      _GLFWwindow* window = (_GLFWwindow*) handle;
      _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
  
      if (_glfw.platform.platformID != GLFW_PLATFORM_X11)
      {
          _glfwInputError(GLFW_PLATFORM_UNAVAILABLE, "GLX: Platform not initialized");
          return NULL;
      }
  
      if (window->context.source != GLFW_NATIVE_CONTEXT_API)
      {
          _glfwInputError(GLFW_NO_WINDOW_CONTEXT, NULL);
          return NULL;
      }
  
      return window->context.glx.handle;
  }
  
  GLFWAPI GLXWindow glfwGetGLXWindow(GLFWwindow* handle)
  {
      _GLFWwindow* window = (_GLFWwindow*) handle;
      _GLFW_REQUIRE_INIT_OR_RETURN(None);
  
      if (_glfw.platform.platformID != GLFW_PLATFORM_X11)
      {
          _glfwInputError(GLFW_PLATFORM_UNAVAILABLE, "GLX: Platform not initialized");
          return None;
      }
  
      if (window->context.source != GLFW_NATIVE_CONTEXT_API)
      {
          _glfwInputError(GLFW_NO_WINDOW_CONTEXT, NULL);
          return None;
      }
  
      return window->context.glx.window;
  }
  
  