c4droid triangle exemple opengl

// C++ Headers
#include <string>
#include <iostream>

// OpenGL / glew Headers
#define GL3_PROTOTYPES 1
//#include <GL/glew.h>

// SDL2 Headers
#include <SDL2/SDL.h>

#include <EGL/egl.h>
#include <GLES/gl.h>

#include <android/sensor.h>
#include <android/log.h>
#include <android_native_app_glue.h>
//#include "SDL/SDL_opengl.h"

//Screen attributes
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;
#include <GLES2/gl2.h>
#include <SDL2/SDL.h>

struct myData {
    SDL_Window *window;
    SDL_GLContext context;
};

const GLchar vertex[] =
       "attribute vec4 position;    \n"
    "void main()                  \n"
    "{                            \n"
    "   gl_Position = vec4(position.xyz, 1.0);  \n"
    "}                            \n";

const GLchar fragment[] =
    "precision mediump float;\n"
    "void main()                                  \n"
    "{                                            \n"
    "  gl_FragColor = vec4 (0.0, 1.0, 1.0, 1.0 );\n"
    "}                                            \n";



GLuint loadShader(GLuint program, GLenum type, const GLchar *shaderSrc) {
    GLuint shader;
    shader = glCreateShader(type);
    glShaderSource(shader, 1, &shaderSrc, NULL);
    glCompileShader(shader);
    glAttachShader(program, shader);
    return 0;
}

int sdlInit(myData *data) {
    SDL_Init(SDL_INIT_VIDEO);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    data->window = SDL_CreateWindow("Demo", 0, 0, 512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
    data->context = SDL_GL_CreateContext(data->window);

    return 0;
}

int glInit(myData *data) {
    GLuint programObject;
        GLuint vbo;
    glGenBuffers(1, &vbo);

    GLfloat vertices[] = {0.0f, 0.9f, 0.9f, -0.9f, -0.9f, -0.9f};


    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    programObject = glCreateProgram();
    loadShader(programObject, GL_VERTEX_SHADER, vertex);
    loadShader(programObject, GL_FRAGMENT_SHADER, fragment);
    glLinkProgram(programObject);
    glUseProgram(programObject);
    GLint posAttrib = glGetAttribLocation(  programObject , "position");
    glEnableVertexAttribArray(posAttrib);
    glVertexAttribPointer(posAttrib,2, GL_FLOAT, GL_FALSE, 0, 0);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glViewport(0, 0, 512, 512);

    return 0;
}

int loopFunc(myData *data) {
    SDL_Event event;
    while (SDL_PollEvent(&event)) {
        if (event.type == SDL_QUIT) {
            return 1;
        }
    }

      // Clear the screen to black
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // Draw a triangle from the 3 vertices
        glDrawArrays(GL_TRIANGLES, 0, 3);
    SDL_GL_SwapWindow(data->window);

    return 0;
}

void sdlQuit(myData *data) {
    SDL_GL_DeleteContext(data->context);
    SDL_DestroyWindow(data->window);
    SDL_Quit();
    return;
}

int main() {
    myData data;

    sdlInit(&data);

    glInit(&data);

    while (!loopFunc(&data));

    sdlQuit(&data);

    return 0;
}