// Test case for Ubuntu bug #450901 (xserver-xorg-video-intel)
// Written by Camilla Berglund <elmindreda@elmindreda.org>
//
// Triggers the problem when using glDrawElements on (at least one) GMA965 with
// Karmic amd64 and all packages up-to-date as of Sun Nov 1 01:39:14 UTC 2009
//
// Works as expected on (at least one) GMA915 with Jaunty x86 equally up-to-date
//
// Unusual dependencies: libglfw-dev libglew-dev
// Build using: gcc -o ibo ibo.c -lGLEW `pkg-config --libs libglfw`

#include <GL/glew.h>
#include <GL/glfw.h>

#include <stdio.h>
#include <stdlib.h>

typedef struct
{
  GLfloat x;
  GLfloat y;
} Vertex;

// One 1x1 CCW quad
static Vertex vertices[] =
{
  { -0.5f, -0.5f },
  {  0.5f, -0.5f },
  {  0.5f,  0.5f },
  { -0.5f,  0.5f },
};

// Two CCW triangles
static GLuint indices[] =
{
  0, 1, 2,
  0, 2, 3,
};

static void GLFWCALL window_size_callback(int width, int height)
{
  glViewport(0, 0, width, height);
}

int main(void)
{
  GLuint vbuf, ibuf;

  if (!glfwInit())
  {
    fprintf(stderr, "Failed to initialize GLFW\n");
    exit(EXIT_FAILURE);
  }

  if (!glfwOpenWindow(640, 480, 8, 8, 8, 0, 0, 0, GLFW_WINDOW))
  {
    fprintf(stderr, "Failed to initialize GLFW\n");
    glfwTerminate();
    exit(EXIT_FAILURE);
  }

  glfwSetWindowSizeCallback(window_size_callback);
  glfwSetWindowTitle("Press Space for bug");
  glfwSwapInterval(1);

  if (glewInit() != GLEW_OK)
  {
    fprintf(stderr, "Failed to initialize GLEW\n");
    glfwTerminate();
    exit(EXIT_FAILURE);
  }

  glGenBuffersARB(1, &vbuf);
  glBindBufferARB(GL_ARRAY_BUFFER_ARB, vbuf);
  glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(vertices), vertices, GL_STATIC_DRAW_ARB);
  glEnableClientState(GL_VERTEX_ARRAY);
  glVertexPointer(2, GL_FLOAT, 0, NULL);

  glGenBuffersARB(1, &ibuf);
  glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, ibuf);
  glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB, sizeof(indices), indices, GL_STATIC_DRAW_ARB);

  glMatrixMode(GL_PROJECTION);
  glOrtho(-1.f, 1.f, -1.f, 1.f, 1.f, -1.f);
  glMatrixMode(GL_MODELVIEW);

  glColor3f(1.f, 0.f, 0.f);

  do
  {
    glClear(GL_COLOR_BUFFER_BIT);

    glLoadIdentity();
    glRotatef(glfwGetTime() * 100.f, 0.f, 0.f, 1.f);

    if (glfwGetKey(GLFW_KEY_SPACE) == GLFW_PRESS)
      glDrawElements(GL_TRIANGLES, sizeof(indices) / sizeof(GLuint), GL_UNSIGNED_INT, NULL);
    else
      glDrawArrays(GL_TRIANGLE_FAN, 0, sizeof(vertices) / sizeof(Vertex));

    glfwSwapBuffers();
  }
  while (glfwGetWindowParam(GLFW_OPENED));

  glfwTerminate();
  exit(EXIT_SUCCESS);
}