windows-libangle-glfw3-gles2.cpp

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

#define GLFW_INCLUDE_ES2
#include <GLFW/glfw3.h>

static const GLuint WIDTH = 800;
static const GLuint HEIGHT = 600;
static const GLchar* vertex_shader_source =
"#version 100\n"
"attribute vec3 position;\n"
"void main() {\n"
"   gl_Position = vec4(position, 1.0);\n"
"}\n";
static const GLchar* fragment_shader_source =
"#version 100\n"
"void main() {\n"
"   gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
"}\n";
static const GLfloat vertices[] = {
        0.0f,  0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
    -0.5f, -0.5f, 0.0f,
};

std::string ReadShaderFromFile(const char *filePath);

GLint common_get_shader_program(const char *vertex_shader_source, const char *fragment_shader_source) {
    enum Consts { INFOLOG_LEN = 512 };
    GLchar infoLog[INFOLOG_LEN];
    GLint fragment_shader;
    GLint shader_program;
    GLint success;
    GLint vertex_shader;

    /* Vertex shader */
    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    std::string vshader = ReadShaderFromFile("C:\\Users\\psundareson\\source\\repos\\zillion\\zillion\\vsimpleshader.glsl");
    const char* vshaderstr = vshader.c_str();
    glShaderSource(vertex_shader, 1, &vshaderstr, NULL);
    glCompileShader(vertex_shader);
    glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(vertex_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Fragment shader */
    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    std::string fshader = ReadShaderFromFile("C:\\Users\\psundareson\\source\\repos\\zillion\\zillion\\fsimpleshader.glsl");
    const char* fshaderstr = fshader.c_str();

    glShaderSource(fragment_shader, 1, &fshaderstr, NULL);
    glCompileShader(fragment_shader);
    glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragment_shader, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", infoLog);
    }

    /* Link shaders */
    shader_program = glCreateProgram();
    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glLinkProgram(shader_program);
    glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shader_program, INFOLOG_LEN, NULL, infoLog);
        printf("ERROR::SHADER::PROGRAM::LINKING_FAILED\n%s\n", infoLog);
    }

    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);
    return shader_program;
}

int main(void) {
    GLuint shader_program, vbo;
    GLint pos;
    GLFWwindow* window;

    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_CREATION_API, GLFW_EGL_CONTEXT_API);
    glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
    glfwMakeContextCurrent(window);

    printf("GL_VERSION  : %s\n", glGetString(GL_VERSION));
    printf("GL_RENDERER : %s\n", glGetString(GL_RENDERER));

    shader_program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
    pos = glGetAttribLocation(shader_program, "position");

    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    //glViewport(0, 0, WIDTH, HEIGHT);

    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(pos, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
    glEnableVertexAttribArray(pos);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    GLint progress_loc = glGetUniformLocation(shader_program, "progress");

    float curr_progress = 0.0;
    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();
        glClear(GL_COLOR_BUFFER_BIT);
        glUseProgram(shader_program);

        glUniform1f(progress_loc, curr_progress);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glfwSwapBuffers(window);

        curr_progress += 0.001;
        if (curr_progress > 0.9)
            curr_progress = 0.0;
    }
    glDeleteBuffers(1, &vbo);
    glfwTerminate();
    return EXIT_SUCCESS;
}

EGL initiatlisation added to the orig cdoe from - https://stackoverflow.com/questions/12045488/any-gles-examples-in-c-on-x86-linux