/*
THIS WORK, INCLUDING THE SOURCE CODE, DOCUMENTATION
AND RELATED MEDIA AND DATA, IS PLACED INTO THE PUBLIC DOMAIN.

THE ORIGINAL AUTHOR IS KYLE FOLEY.

THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY
OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF
MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE,
ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE
RESULTING FROM THE USE, MODIFICATION, OR
REDISTRIBUTION OF THIS SOFTWARE.
*/

#ifndef __EMSCRIPTEN__
#define USE_GLEW 1
#endif

#if USE_GLEW
#include "GL/glew.h"
#endif

#include "SDL/SDL.h"
#if !USE_GLEW
#include "SDL/SDL_opengl.h"
#endif

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

int main(int argc, char *argv[])
{
    // testing
    GLint tempInt;
    GLboolean tempBool;
    void *tempPtr;

    SDL_Surface *screen;
    if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
        printf("Unable to initialize SDL: %s\n", SDL_GetError());
        return 1;
    }

    SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
    screen = SDL_SetVideoMode( 640, 480, 24, SDL_OPENGL );
    if ( !screen ) {
        printf("Unable to set video mode: %s\n", SDL_GetError());
        return 1;
    }
    
    glClearColor( 0, 0, 0, 0 );
    glClear( GL_COLOR_BUFFER_BIT );

    // Create a texture

    GLint boundTex = 123;
    assert(!glGetError());
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &boundTex);
    assert(!glGetError());
    assert(boundTex == 0);

    GLuint texture;
    glGenTextures( 1, &texture );
    glBindTexture( GL_TEXTURE_2D, texture );

    assert(!glGetError());
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &boundTex);
    assert(!glGetError());
    assert(boundTex == texture);

    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    GLubyte textureData[16*16*4];
    for (int x = 0; x < 16; x++) {
      for (int y = 0; y < 16; y++) {
        *((int*)&textureData[(x*16 + y) * 4]) = x*16 + ((y*16) << 8);
      }
    }
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 16, 16, 0, 
                  GL_RGBA, GL_UNSIGNED_BYTE, textureData );

    // Create a second texture

    GLuint texture2;
    glGenTextures( 1, &texture2 );
    glBindTexture( GL_TEXTURE_2D, texture2 );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    GLubyte texture2Data[] = { 0xff,    0,    0, 0xff,
                                  0, 0xff,    0, 0xaa,
                                  0,    0, 0xff, 0x55,
                               0x80, 0x90, 0x70,    0 };
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0,
                  GL_RGBA, GL_UNSIGNED_BYTE, texture2Data );
    
    // BEGIN

#if USE_GLEW
    glewInit();
#endif

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    // original: glFrustum(-0.6435469817188064, 0.6435469817188064 ,-0.48266022190470925, 0.48266022190470925 ,0.5400000214576721, 2048);
    glFrustum(-0.6435469817188064, 0.1435469817188064 ,-0.48266022190470925, 0.88266022190470925 ,0.5400000214576721, 2048);
    glRotatef(-30, 1, 1, 1);
    //GLfloat pm[] = { 1.372136116027832, 0, 0, 0, 0, 0.7910231351852417, 0, 0, -0.6352481842041016, 0.29297152161598206, -1.0005275011062622, -1, 0, 0, -1.080284833908081, 0 };
    //glLoadMatrixf(pm);

    glMatrixMode(GL_MODELVIEW);
    GLfloat matrixData[] = { -1, 0, 0, 0,
                              0, 0,-1, 0,
                              0, 1, 0, 0,
                              0, 0, 0, 1 };
    glLoadMatrixf(matrixData);
    //glTranslated(-512,-512,-527); // XXX this should be uncommented, but if it is then nothing is shown

    glEnable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST);

    glClear(GL_DEPTH_BUFFER_BIT);

    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    glActiveTexture(GL_TEXTURE0);

    glGetBooleanv(GL_VERTEX_ARRAY, &tempBool); assert(!tempBool);
    glEnableClientState(GL_VERTEX_ARRAY);
    glGetBooleanv(GL_VERTEX_ARRAY, &tempBool); assert(tempBool);

    GLuint arrayBuffer, elementBuffer;
    glGenBuffers(1, &arrayBuffer);
    glGenBuffers(1, &elementBuffer);

    GLubyte arrayData[] = {
/*
[0, 0,   0, 67] ==>  128 float
[0, 0, 128, 67] ==>  256 float
[0, 0,   0, 68] ==>  512 float
[0, 0, 128, 68] ==> 1024 float

[vertex x        ] [vertex y         ] [vertex z         ] [nr]                [texture u        ] [texture v        ] [lm u   ] [lm v   ] [color r,g,b,a    ] */
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128, //  0
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128, //  1
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  2
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  3
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128, //  4
  0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  67,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128, //  5
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  6
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  7
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  8
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, //  9
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0, 128,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 10
  0,   0,   0,   0,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 11
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 12
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  67,   0,   0,   0,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 13
  0,   0, 128,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  67,   0,   0, 128,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 14
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  67,   0,   0, 128,  67,   0,   0,   0,   0, 128, 128, 128, 128, // 15

  0,   0,   0,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,   0,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,   0,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0,   0,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0, 128,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128,
  0,   0, 128,  68,   0,   0, 128,  68,   0,   0,   0,  68,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, 128, 128, 128, 128
    };
    assert(sizeof(arrayData) == 1408);
    glBindBuffer(GL_ARRAY_BUFFER, arrayBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(arrayData), arrayData, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    GLushort elementData[] = { 1, 2, 0, 2, 3, 0, 5, 6, 4, 6, 7, 4, 9, 10, 8, 10, 11, 8, 13, 14, 12, 14, 15, 12 };
    assert(sizeof(elementData) == 48);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elementData), elementData, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

    glBindBuffer(GL_ARRAY_BUFFER, arrayBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBuffer);

    // sauer vertex data is apparently 0-12: V3F, 12: N1B, 16-24: T2F, 24-28: T2S, 28-32: C4B
    glVertexPointer(3, GL_FLOAT, 32, (void*)0); // all these apply to the ARRAY_BUFFER that is bound
    glTexCoordPointer(2, GL_FLOAT, 32, (void*)16);

    glClientActiveTexture(GL_TEXTURE1); // XXX seems to be ignored in native build
    glTexCoordPointer(2, GL_SHORT, 32, (void*)24);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_SIZE, &tempInt); assert(tempInt == 2);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_TYPE, &tempInt); assert(tempInt == GL_SHORT);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_STRIDE, &tempInt); assert(tempInt == 32);
    glGetPointerv(GL_TEXTURE_COORD_ARRAY_POINTER, &tempPtr); assert(tempPtr == (void *)24);

    glClientActiveTexture(GL_TEXTURE0); // likely not needed, it is a cleanup
    glNormalPointer(GL_BYTE, 32, (void*)12);
    glColorPointer(4, GL_UNSIGNED_BYTE, 32, (void*)28);

    glGetPointerv(GL_VERTEX_ARRAY_POINTER, &tempPtr); assert(tempPtr == (void *)0);
    glGetPointerv(GL_COLOR_ARRAY_POINTER, &tempPtr); assert(tempPtr == (void *)28);
    glGetPointerv(GL_TEXTURE_COORD_ARRAY_POINTER, &tempPtr); assert(tempPtr == (void *)16);
    glGetIntegerv(GL_VERTEX_ARRAY_SIZE, &tempInt); assert(tempInt == 3);
    glGetIntegerv(GL_VERTEX_ARRAY_TYPE, &tempInt); assert(tempInt == GL_FLOAT);
    glGetIntegerv(GL_VERTEX_ARRAY_STRIDE, &tempInt); assert(tempInt == 32);
    glGetIntegerv(GL_COLOR_ARRAY_SIZE, &tempInt); assert(tempInt == 4);
    glGetIntegerv(GL_COLOR_ARRAY_TYPE, &tempInt); assert(tempInt == GL_UNSIGNED_BYTE);
    glGetIntegerv(GL_COLOR_ARRAY_STRIDE, &tempInt); assert(tempInt == 32);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_SIZE, &tempInt); assert(tempInt == 2);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_TYPE, &tempInt); assert(tempInt == GL_FLOAT);
    glGetIntegerv(GL_TEXTURE_COORD_ARRAY_STRIDE, &tempInt); assert(tempInt == 32);
    glGetBooleanv(GL_VERTEX_ARRAY, &tempBool); assert(tempBool);

    glBindTexture(GL_TEXTURE_2D, texture); // diffuse?
    glActiveTexture(GL_TEXTURE0);
    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, texture2); // lightmap?
    glActiveTexture(GL_TEXTURE0);

    GLint ok;

    const char *vertexShader = "uniform vec4 texgenscroll[2];\n"
                               "void main(void)\n"
                               "{\n"
                               "    gl_Position = ftransform();\n"
                               "    gl_TexCoord[0].xy = 0.01 * (0.0*gl_MultiTexCoord0.xy + dot(gl_MultiTexCoord0.xy, texgenscroll[0].xy) - dot(gl_MultiTexCoord0.zw, texgenscroll[0].zw));\n" 
                               "    gl_TexCoord[1].xy = 0.01 * dot(gl_MultiTexCoord0.xy, texgenscroll[1].yz) + texgenscroll[1].xw;\n"
                               "}\n";
    const char *fragmentShader = "uniform vec4 colorparams;\n"
                                 "uniform sampler2D diffusemap, lightmap;\n"
                                 "void main(void)\n"
                                 "{\n"
                                 "    vec4 diffuse = texture2D(diffusemap, gl_TexCoord[0].xy);\n"
                                 "    vec4 lm = texture2D(lightmap, gl_TexCoord[1].xy);\n"
                                 "    diffuse *= colorparams;\n"
                                 "    gl_FragColor = diffuse * lm;\n"
                                 "}\n";

    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vertexShader, NULL);
    glCompileShader(vs);
    glGetShaderiv(vs, GL_COMPILE_STATUS, &ok);
    assert(ok);

    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fragmentShader, NULL);
    glCompileShader(fs);
    glGetShaderiv(fs, GL_COMPILE_STATUS, &ok);
    assert(ok);

    GLuint program = glCreateProgram();

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glGetProgramiv(program, GL_LINK_STATUS, &ok);
    assert(ok);

    glUseProgram(program);

    GLint lightmapLocation = glGetUniformLocation(program, "lightmap");
    assert(lightmapLocation >= 0);
    assert(lightmapLocation == glGetUniformLocation(program, "lightmap")); // must get identical ids
    glLinkProgram(program);
    glGetProgramiv(program, GL_LINK_STATUS, &ok);
    assert(ok);
    assert(lightmapLocation != glGetUniformLocation(program, "lightmap")); // must NOT get identical ids, we re-linked!
    lightmapLocation = glGetUniformLocation(program, "lightmap");
    assert(lightmapLocation == glGetUniformLocation(program, "lightmap")); // must get identical ids

    glUniform1i(lightmapLocation, 1); // sampler2D? Is it the texture unit?

    GLint diffusemapLocation = glGetUniformLocation(program, "diffusemap");
    assert(diffusemapLocation >= 0);
    glUniform1i(diffusemapLocation, 0);

    GLint texgenscrollLocation = glGetUniformLocation(program, "texgenscroll");
    assert(texgenscrollLocation >= 0);

    GLint colorparamsLocation = glGetUniformLocation(program, "colorparams");
    assert(colorparamsLocation >= 0);

    //GLfloat texgenscrollData[] = { 0, 0, 0, 0, 0, 0, 0, 0 };
    GLfloat texgenscrollData[] = { 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 };
    GLfloat *storage = (GLfloat*)malloc(sizeof(texgenscrollData)); // copy data to the heap, test for SPLIT_MEMORY subarray on chunk > 0
    memcpy(storage, texgenscrollData, sizeof(texgenscrollData));
    glUniform4fv(texgenscrollLocation, 2, storage);

    GLfloat colorparamsData[] = { 2, 2, 2, 1 };
    glUniform4fv(colorparamsLocation, 1, colorparamsData);

    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)12);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*) 0);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)24);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (void*)36);

    // END

    SDL_GL_SwapBuffers();
  
#ifndef __EMSCRIPTEN__
    SDL_Delay(1500);
#endif

    SDL_Quit();
    
    return 0;
}
