text: //========================================================================
  // Gamma correction test program
  // Copyright (c) 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.
  //
  //========================================================================
  //
  // This program is used to test the gamma correction functionality for
  // both full screen and windowed mode windows
  //
  //========================================================================
  
  #define GLAD_GL_IMPLEMENTATION
  #include <glad/gl.h>
  #define GLFW_INCLUDE_NONE
  #include <GLFW/glfw3.h>
  
  #define NK_IMPLEMENTATION
  #define NK_INCLUDE_FIXED_TYPES
  #define NK_INCLUDE_FONT_BAKING
  #define NK_INCLUDE_DEFAULT_FONT
  #define NK_INCLUDE_DEFAULT_ALLOCATOR
  #define NK_INCLUDE_VERTEX_BUFFER_OUTPUT
  #define NK_INCLUDE_STANDARD_VARARGS
  #define NK_BUTTON_TRIGGER_ON_RELEASE
  #include <nuklear.h>
  
  #define NK_GLFW_GL2_IMPLEMENTATION
  #include <nuklear_glfw_gl2.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  static void error_callback(int error, const char* description)
  {
      fprintf(stderr, "Error: %s\n", description);
  }
  
  static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
  {
      if (action == GLFW_PRESS && key == GLFW_KEY_ESCAPE)
          glfwSetWindowShouldClose(window, GLFW_TRUE);
  }
  
  static void chart_ramp_array(struct nk_context* nk,
                               struct nk_color color,
                               int count, unsigned short int* values)
  {
      if (nk_chart_begin_colored(nk, NK_CHART_LINES,
                                 color, nk_rgb(255, 255, 255),
                                 count, 0, 65535))
      {
          int i;
          for (i = 0;  i < count;  i++)
          {
              char buffer[1024];
              if (nk_chart_push(nk, values[i]))
              {
                  snprintf(buffer, sizeof(buffer), "#%u: %u (%0.5f) ",
                           i, values[i], values[i] / 65535.f);
                  nk_tooltip(nk, buffer);
              }
          }
  
          nk_chart_end(nk);
      }
  }
  
  int main(int argc, char** argv)
  {
      GLFWmonitor* monitor = NULL;
      GLFWwindow* window;
      GLFWgammaramp orig_ramp;
      struct nk_context* nk;
      struct nk_font_atlas* atlas;
      float gamma_value = 1.f;
  
      glfwSetErrorCallback(error_callback);
  
      if (!glfwInit())
          exit(EXIT_FAILURE);
  
      monitor = glfwGetPrimaryMonitor();
  
      glfwWindowHint(GLFW_SCALE_TO_MONITOR, GLFW_TRUE);
      glfwWindowHint(GLFW_WIN32_KEYBOARD_MENU, GLFW_TRUE);
  
      window = glfwCreateWindow(800, 400, "Gamma Test", NULL, NULL);
      if (!window)
      {
          glfwTerminate();
          exit(EXIT_FAILURE);
      }
  
      {
          const GLFWgammaramp* ramp = glfwGetGammaRamp(monitor);
          if (!ramp)
          {
              glfwTerminate();
              exit(EXIT_FAILURE);
          }
  
          const size_t array_size = ramp->size * sizeof(short);
          orig_ramp.size = ramp->size;
          orig_ramp.red = malloc(array_size);
          orig_ramp.green = malloc(array_size);
          orig_ramp.blue = malloc(array_size);
          memcpy(orig_ramp.red, ramp->red, array_size);
          memcpy(orig_ramp.green, ramp->green, array_size);
          memcpy(orig_ramp.blue, ramp->blue, array_size);
      }
  
      glfwMakeContextCurrent(window);
      gladLoadGL(glfwGetProcAddress);
      glfwSwapInterval(1);
  
      nk = nk_glfw3_init(window, NK_GLFW3_INSTALL_CALLBACKS);
      nk_glfw3_font_stash_begin(&atlas);
      nk_glfw3_font_stash_end();
  
      glfwSetKeyCallback(window, key_callback);
  
      while (!glfwWindowShouldClose(window))
      {
          int width, height;
          struct nk_rect area;
  
          glfwGetWindowSize(window, &width, &height);
          area = nk_rect(0.f, 0.f, (float) width, (float) height);
          nk_window_set_bounds(nk, "", area);
  
          glClear(GL_COLOR_BUFFER_BIT);
          nk_glfw3_new_frame();
          if (nk_begin(nk, "", area, 0))
          {
              const GLFWgammaramp* ramp;
  
              nk_layout_row_dynamic(nk, 30, 3);
              if (nk_slider_float(nk, 0.1f, &gamma_value, 5.f, 0.1f))
                  glfwSetGamma(monitor, gamma_value);
              nk_labelf(nk, NK_TEXT_LEFT, "%0.1f", gamma_value);
              if (nk_button_label(nk, "Revert"))
                  glfwSetGammaRamp(monitor, &orig_ramp);
  
              ramp = glfwGetGammaRamp(monitor);
  
              nk_layout_row_dynamic(nk, height - 60.f, 3);
              chart_ramp_array(nk, nk_rgb(255, 0, 0), ramp->size, ramp->red);
              chart_ramp_array(nk, nk_rgb(0, 255, 0), ramp->size, ramp->green);
              chart_ramp_array(nk, nk_rgb(0, 0, 255), ramp->size, ramp->blue);
          }
  
          nk_end(nk);
          nk_glfw3_render(NK_ANTI_ALIASING_ON);
  
          glfwSwapBuffers(window);
          glfwWaitEventsTimeout(1.0);
      }
  
      free(orig_ramp.red);
      free(orig_ramp.green);
      free(orig_ramp.blue);
  
      nk_glfw3_shutdown();
      glfwTerminate();
      exit(EXIT_SUCCESS);
  }
  
  