text: //========================================================================
  // Multithreading test
  // Copyright (c) Camilla Berglund <elmindreda@elmindreda.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.
  //
  //========================================================================
  //
  // This test is intended to verify whether the OpenGL context part of
  // the GLFW API is able to be used from multiple threads
  //
  //========================================================================
  
  #include <GL/glfw3.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <math.h>
  #include <assert.h>
  
  #include "tinycthread.h"
  
  typedef struct
  {
      GLFWwindow window;
      const char* title;
      float r, g, b;
      thrd_t id;
  } Thread;
  
  static volatile GLboolean running = GL_TRUE;
  
  static int thread_main(void* data)
  {
      const Thread* thread = (const Thread*) data;
  
      glfwMakeContextCurrent(thread->window);
      assert(glfwGetCurrentContext() == thread->window);
  
      glfwSwapInterval(1);
  
      while (running)
      {
          const float v = (float) fabs(sin(glfwGetTime() * 2.f));
          glClearColor(thread->r * v, thread->g * v, thread->b * v, 0.f);
  
          glClear(GL_COLOR_BUFFER_BIT);
          glfwSwapBuffers(thread->window);
      }
  
      glfwMakeContextCurrent(NULL);
      return 0;
  }
  
  int main(void)
  {
      int i, result;
      Thread threads[] =
      {
          { NULL, "Red", 1.f, 0.f, 0.f, 0 },
          { NULL, "Green", 0.f, 1.f, 0.f, 0 },
          { NULL, "Blue", 0.f, 0.f, 1.f, 0 }
      };
      const int count = sizeof(threads) / sizeof(Thread);
  
      if (!glfwInit())
      {
          fprintf(stderr, "Failed to initialize GLFW: %s\n",
                  glfwErrorString(glfwGetError()));
          exit(EXIT_FAILURE);
      }
  
      for (i = 0;  i < count;  i++)
      {
          threads[i].window = glfwCreateWindow(200, 200,
                                               GLFW_WINDOWED,
                                               threads[i].title,
                                               NULL);
          if (!threads[i].window)
          {
              fprintf(stderr, "Failed to open GLFW window: %s\n",
                      glfwErrorString(glfwGetError()));
              exit(EXIT_FAILURE);
          }
  
          glfwSetWindowPos(threads[i].window, 200 + 250 * i, 200);
  
          if (thrd_create(&threads[i].id, thread_main, threads + i) !=
              thrd_success)
          {
              fprintf(stderr, "Failed to create secondary thread\n");
              exit(EXIT_FAILURE);
          }
      }
  
      while (running)
      {
          assert(glfwGetCurrentContext() == NULL);
  
          glfwWaitEvents();
  
          for (i = 0;  i < count;  i++)
          {
              if (glfwGetWindowParam(threads[i].window, GLFW_CLOSE_REQUESTED))
                  running = GL_FALSE;
          }
      }
  
      for (i = 0;  i < count;  i++)
          thrd_join(threads[i].id, &result);
  
      exit(EXIT_SUCCESS);
  }
  
  