gltest.c

#include <assert.h>
#include <stdio.h>

#include <GL/gl.h>
#include <GL/glext.h>
#include "GLFW/glfw3.h"

PFNGLGENFRAMEBUFFERSEXTPROC glGenFramebuffersEXT;
PFNGLBINDFRAMEBUFFEREXTPROC glBindFramebufferEXT;
PFNGLFRAMEBUFFERTEXTURE2DEXTPROC glFramebufferTexture2DEXT;
PFNGLGENRENDERBUFFERSEXTPROC glGenRenderbuffersEXT;
PFNGLBINDRENDERBUFFEREXTPROC glBindRenderbufferEXT;
PFNGLRENDERBUFFERSTORAGEEXTPROC glRenderbufferStorageEXT;
PFNGLFRAMEBUFFERRENDERBUFFEREXTPROC glFramebufferRenderbufferEXT;
PFNGLCHECKFRAMEBUFFERSTATUSEXTPROC glCheckFramebufferStatusEXT;

int main() {
  if (!glfwInit()) {
    assert(0);
  }
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);

  GLFWwindow* window = glfwCreateWindow(100, 100, "Foo", NULL, NULL);
  glfwMakeContextCurrent(window);

  int t;
  glGenTextures(1, &t);
  glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
  glBindTexture(GL_TEXTURE_2D, t);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 100, 100, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

  glGenFramebuffersEXT = (PFNGLGENFRAMEBUFFERSEXTPROC)wglGetProcAddress("glGenFramebuffersEXT");
  glBindFramebufferEXT = (PFNGLBINDFRAMEBUFFEREXTPROC)wglGetProcAddress("glBindFramebufferEXT");
  glFramebufferTexture2DEXT = (PFNGLFRAMEBUFFERTEXTURE2DEXTPROC)wglGetProcAddress("glFramebufferTexture2DEXT");
  glGenRenderbuffersEXT = (PFNGLGENRENDERBUFFERSEXTPROC)wglGetProcAddress("glGenRenderbuffersEXT");
  glBindRenderbufferEXT = (PFNGLBINDRENDERBUFFEREXTPROC)wglGetProcAddress("glBindRenderbufferEXT");
  glRenderbufferStorageEXT = (PFNGLRENDERBUFFERSTORAGEEXTPROC)wglGetProcAddress("glRenderbufferStorageEXT");
  glFramebufferRenderbufferEXT = (PFNGLFRAMEBUFFERRENDERBUFFEREXTPROC)wglGetProcAddress("glFramebufferRenderbufferEXT");
  glCheckFramebufferStatusEXT = (PFNGLCHECKFRAMEBUFFERSTATUSEXTPROC)wglGetProcAddress("glCheckFramebufferStatusEXT");

  int f;
  glGenFramebuffersEXT(1, &f);
  glBindFramebufferEXT(GL_FRAMEBUFFER, f);
  glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, t, 0);
  if (glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
    assert(0);
  }
  {
    int err = glGetError();
    if (err != GL_NO_ERROR) {
      char msg[1024];
      sprintf(msg, "before resizing: %d\n", err);
      MessageBox(NULL, msg, "test", 0);
      assert(0);
    }
  }
  glBindFramebufferEXT(GL_FRAMEBUFFER, 0);
  glfwSetWindowSize(window, 120, 120);
  {
    int err = glGetError();
    if (err != GL_NO_ERROR) {
      char msg[1024];
      sprintf(msg, "after resizing: %d\n", err);
      MessageBox(NULL, msg, "test", 0);
      assert(0);
    }
  }

  while (!glfwWindowShouldClose(window)) {
    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  glfwTerminate();
}