author Martin Vogt <>
Wed, 22 Aug 2012 23:16:30 -0400
changeset 105737 e461878f0567a55a1eee4f118f8c970f618929e7
parent 95919 f4157e8c410708d76703f19e4dfb61859bfe32d8
child 105738 920d71aa1d2cac4290607eca2aa9e973a69ae387
permissions -rw-r--r--
Bug 680644 - Let glxtest use a XWindow instead of a GLXPixmap - r=bjacob This simplifies code and avoids a X server crash with certain FGLRX setups.

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=8 et :
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at */

// Explanation: See bug 639842. Safely getting GL driver info on X11 is hard, because the only way to do
// that is to create a GL context and call glGetString(), but with bad drivers,
// just creating a GL context may crash.
// This file implements the idea to do that in a separate process.
// The only non-static function here is fire_glxtest_process(). It creates a pipe, publishes its 'read' end as the
// mozilla::widget::glxtest_pipe global variable, forks, and runs that GLX probe in the child process,
// which runs the glxtest() static function. This creates a X connection, a GLX context, calls glGetString, and writes that
// to the 'write' end of the pipe.

#include <cstdio>
#include <cstdlib>
#include <unistd.h>
#include <GL/gl.h>
#include <GL/glx.h>
#include <dlfcn.h>
#include "nscore.h"

#include <fcntl.h>

#ifdef __SUNPRO_CC
#include <stdio.h>

namespace mozilla {
namespace widget {
// the read end of the pipe, which will be used by GfxInfo
extern int glxtest_pipe;
// the PID of the glxtest process, to pass to waitpid()
extern pid_t glxtest_pid;

// the write end of the pipe, which we're going to write to
static int write_end_of_the_pipe = -1;

// C++ standard collides with C standard in that it doesn't allow casting void* to function pointer types.
// So the work-around is to convert first to size_t.
template<typename func_ptr_type>
static func_ptr_type cast(void *ptr)
  return reinterpret_cast<func_ptr_type>(

static void fatal_error(const char *str)
  write(write_end_of_the_pipe, str, strlen(str));
  write(write_end_of_the_pipe, "\n", 1);

static int
x_error_handler(Display *, XErrorEvent *ev)
  enum { bufsize = 1024 };
  char buf[bufsize];
  int length = snprintf(buf, bufsize,
                        "X error occurred in GLX probe, error_code=%d, request_code=%d, minor_code=%d\n",
  write(write_end_of_the_pipe, buf, length);
  return 0;

static void glxtest()
  // we want to redirect to /dev/null stdout, stderr, and while we're at it,
  // any PR logging file descriptors. To that effect, we redirect all positive
  // file descriptors up to what open() returns here. In particular, 1 is stdout and 2 is stderr.
  int fd = open("/dev/null", O_WRONLY);
  for (int i = 1; i < fd; i++)
    dup2(fd, i);

  ///// Open libGL and load needed symbols /////
#ifdef __OpenBSD__
  #define LIBGL_FILENAME ""
  #define LIBGL_FILENAME ""
  void *libgl = dlopen(LIBGL_FILENAME, RTLD_LAZY);
  if (!libgl)
    fatal_error("Unable to load " LIBGL_FILENAME);
  typedef void* (* PFNGLXGETPROCADDRESS) (const char *);
  PFNGLXGETPROCADDRESS glXGetProcAddress = cast<PFNGLXGETPROCADDRESS>(dlsym(libgl, "glXGetProcAddress"));
  if (!glXGetProcAddress)
    fatal_error("Unable to find glXGetProcAddress in " LIBGL_FILENAME);

  typedef GLXFBConfig* (* PFNGLXQUERYEXTENSION) (Display *, int *, int *);
  PFNGLXQUERYEXTENSION glXQueryExtension = cast<PFNGLXQUERYEXTENSION>(glXGetProcAddress("glXQueryExtension"));

  typedef GLXFBConfig* (* PFNGLXQUERYVERSION) (Display *, int *, int *);
  PFNGLXQUERYVERSION glXQueryVersion = cast<PFNGLXQUERYVERSION>(dlsym(libgl, "glXQueryVersion"));

  typedef GLXFBConfig* (* PFNGLXCHOOSEFBCONFIG) (Display *, int, const int *, int *);
  PFNGLXCHOOSEFBCONFIG glXChooseFBConfig = cast<PFNGLXCHOOSEFBCONFIG>(glXGetProcAddress("glXChooseFBConfig"));

  typedef XVisualInfo* (* PFNGLXGETVISUALFROMFBCONFIG) (Display *, GLXFBConfig);

  typedef GLXContext (* PFNGLXCREATENEWCONTEXT) (Display *, GLXFBConfig, int, GLXContext, Bool);
  PFNGLXCREATENEWCONTEXT glXCreateNewContext = cast<PFNGLXCREATENEWCONTEXT>(glXGetProcAddress("glXCreateNewContext"));

  typedef Bool (* PFNGLXMAKECURRENT) (Display*, GLXDrawable, GLXContext);
  PFNGLXMAKECURRENT glXMakeCurrent = cast<PFNGLXMAKECURRENT>(glXGetProcAddress("glXMakeCurrent"));

  typedef void (* PFNGLXDESTROYCONTEXT) (Display*, GLXContext);
  PFNGLXDESTROYCONTEXT glXDestroyContext = cast<PFNGLXDESTROYCONTEXT>(glXGetProcAddress("glXDestroyContext"));

  typedef GLubyte* (* PFNGLGETSTRING) (GLenum);
  PFNGLGETSTRING glGetString = cast<PFNGLGETSTRING>(glXGetProcAddress("glGetString"));

  if (!glXQueryExtension ||
      !glXQueryVersion ||
      !glXChooseFBConfig ||
      !glXGetVisualFromFBConfig ||
      !glXCreateNewContext ||
      !glXMakeCurrent ||
      !glXDestroyContext ||
    fatal_error("glXGetProcAddress couldn't find required functions");
  ///// Open a connection to the X server /////
  Display *dpy = XOpenDisplay(NULL);
  if (!dpy)
    fatal_error("Unable to open a connection to the X server");
  ///// Check that the GLX extension is present /////
  if (!glXQueryExtension(dpy, NULL, NULL))
    fatal_error("GLX extension missing");


  ///// Get a FBConfig and a visual /////
  int numReturned;
  GLXFBConfig *fbConfigs = glXChooseFBConfig(dpy, DefaultScreen(dpy), NULL, &numReturned );
  if (!fbConfigs)
    fatal_error("No FBConfigs found");
  XVisualInfo *vInfo = glXGetVisualFromFBConfig(dpy, fbConfigs[0]);
  if (!vInfo)
    fatal_error("No visual found for first FBConfig");

  // using a X11 Window instead of a GLXPixmap does not crash
  // fglrx in indirect rendering. bug 680644
  Window win1;
  XSetWindowAttributes swa;
  swa.colormap = XCreateColormap(dpy, RootWindow(dpy, vInfo->screen),
                                 vInfo->visual, AllocNone);
  swa.border_pixel = 0;
  win1 = XCreateWindow(dpy, RootWindow(dpy, vInfo->screen),
                       10, 10, 16, 16,
                       0, vInfo->depth, InputOutput, vInfo->visual,
                       CWBorderPixel | CWColormap, &swa);

  ///// Get a GL context and make it current //////
  GLXContext context = glXCreateNewContext(dpy, fbConfigs[0], GLX_RGBA_TYPE, NULL, True);
  glXMakeCurrent(dpy, win1, context);

  ///// Look for this symbol to determine texture_from_pixmap support /////
  void* glXBindTexImageEXT = glXGetProcAddress("glXBindTexImageEXT"); 

  ///// Get GL vendor/renderer/versions strings /////
  enum { bufsize = 1024 };
  char buf[bufsize];
  const GLubyte *vendorString = glGetString(GL_VENDOR);
  const GLubyte *rendererString = glGetString(GL_RENDERER);
  const GLubyte *versionString = glGetString(GL_VERSION);
  if (!vendorString || !rendererString || !versionString)
    fatal_error("glGetString returned null");

  int length = snprintf(buf, bufsize,
                        glXBindTexImageEXT ? "TRUE" : "FALSE");
  if (length >= bufsize)
    fatal_error("GL strings length too large for buffer size");

  ///// Clean up. Indeed, the parent process might fail to kill us (e.g. if it doesn't need to check GL info)
  ///// so we might be staying alive for longer than expected, so it's important to consume as little memory as
  ///// possible. Also we want to check that we're able to do that too without generating X errors.
  glXMakeCurrent(dpy, None, NULL); // must release the GL context before destroying it
  glXDestroyContext(dpy, context);

  ///// Finally write data to the pipe
  write(write_end_of_the_pipe, buf, length);

/** \returns true in the child glxtest process, false in the parent process */
bool fire_glxtest_process()
  int pfd[2];
  if (pipe(pfd) == -1) {
      return false;
  pid_t pid = fork();
  if (pid < 0) {
      return false;
  if (pid == 0) {
      write_end_of_the_pipe = pfd[1];
      return true;

  mozilla::widget::glxtest_pipe = pfd[0];
  mozilla::widget::glxtest_pid = pid;
  return false;