NeHe Lesson 01: Setting up an OpenGL window

Hi, and welcome to the NeHe lesson 01 done in the D programming language.

This code snippet shows you how to set up SDL to display an OpenGL window, How to use Derelict to load shared libraries and a basic loop for reading input and then drawing the screen.

I'm trying to use documenting comments in the code as specified by Ddoc.

/**
* The first lesson in the NeHe tutorial series.
* Originally written by Jeff Molofee.
*
* Authors: Jeff Molofee
*          Olli Aalto
*/
module lesson01;

import derelict.opengl.gl;
import derelict.opengl.glu;
import derelict.sdl.sdl;

import tango.stdc.stringz;

/// The window title
const char[] WINDOW_TITLE = "NeHe's OpenGL Lesson 01 (D version)";

/// The main loop flag
bool running;

/**
* Module constructor. Here we load the GL, GLU and SDL shared libraries,
* and the initialize SDL.
*/
static this()
{
   DerelictGL.load();
   DerelictGLU.load();
   DerelictSDL.load();

   if (SDL_Init(SDL_INIT_VIDEO) < args =" the" fullscreen =" false;"> 1)
   {
       fullScreen = args[1] == "-fullscreen";
   }

   createGLWindow(WINDOW_TITLE, 640, 480, 16, fullScreen);
   initGL();

   running = true;
   while (running)
   {
       processEvents();

       drawGLScene();

       SDL_GL_SwapBuffers();
       SDL_Delay(10);
  }
}

/**
* Process all the pending events.
*/
void processEvents()
{
   SDL_Event event;
   while (SDL_PollEvent(&event))
   {
       switch (event.type)
       {
           case SDL_KEYUP:
               keyReleased(event.key.keysym.sym);
               break;
           case SDL_QUIT:
               running = false;
               break;
           default:
               break;
       }
   }
}

/**
* Process a key released event.
*/
void keyReleased(int key)
{
   switch (key)
   {
       case SDLK_ESCAPE:
           running = false;
           break;
       default:
           break;
   }
}

/**
* Resize and initialize the OpenGL window.
*/
void resizeGLScene(GLsizei width, GLsizei height)
{
   if (height == 0)
   {
       height = 1;
   }

   // Reset The Current Viewport
   glViewport(0, 0, width, height);

   // Select The Projection Matrix
   glMatrixMode(GL_PROJECTION);

   // Reset The Projection Matrix
   glLoadIdentity();

   // Calculate The Aspect Ratio Of The Window
   gluPerspective(45.0f, cast(GLfloat)width / cast(GLfloat)height,
       0.1f, 100.0f);

   // Select The Modelview Matrix
   glMatrixMode(GL_MODELVIEW);

   // Reset The Modelview Matrix
   glLoadIdentity();
}

/**
* Initialize OpenGL.
*/
void initGL()
{
   // Enables Smooth Shading
   glShadeModel(GL_SMOOTH);

   // Black Background
   glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

   // Depth Buffer Setup
   glClearDepth(1.0f);

   // Enables Depth Testing
   glEnable(GL_DEPTH_TEST);

   // The Type Of Depth Test To Do
   glDepthFunc(GL_LEQUAL);

   // Really Nice Perspective Calculations
   glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}

/**
* The drawing function. Now we only clear the color and depht buffers, so that
* the window stays black.
*/
void drawGLScene()
{
   // Clear The Screen And The Depth Buffer
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   // Reset The Current Modelview Matrix
   glLoadIdentity();
}

/**
* Initializes and opens the SDL window.
*/
void createGLWindow(char[] title, int width, int height, int bits,
   bool fullScreen)
{
   // Set the OpenGL attributes
   SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 5);
   SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 6);
   SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5);
   SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16);
   SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

   // Set the window title
   SDL_WM_SetCaption(toUtf8z(title), null);

   // Note the SDL_DOUBLEBUF flag is not required to enable double
   // buffering when setting an OpenGL video mode.
   // Double buffering is enabled or disabled using the
   // SDL_GL_DOUBLEBUFFER attribute. (See above.)
   int mode = SDL_OPENGL;
   if (fullScreen)
   {
       mode |= SDL_FULLSCREEN;
   }

   // Now open a SDL OpenGL window with the given parameters
   if (SDL_SetVideoMode(width, height, bits, mode) is null)
   {
       throw new Exception("Failed to open OpenGL window: " ~ getSDLError());
   }

   resizeGLScene(width, height);
}

/**
* Get the SDL error as a D string.
*
* Returns: A D string containing the current SDL error.
*/
char[] getSDLError()
{
   return fromUtf8z(SDL_GetError());
}

You can download the code from here.