main

#include <iostream>
#include <cstdlib>
#include <cmath>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include "shader_util.h"

void error_callback(GLint error, const GLchar* description);

GLuint createSqrt(GLuint* vbo, GLuint* ebo, GLfloat dx, GLfloat dy);
void createFigure(GLuint figures[4], GLuint* vbo, GLuint* ebo, GLint x, GLint y, GLfloat d[8]);
void change_tone(GLfloat color[4], GLint op);

int main( ) {
    glfwSetErrorCallback(error_callback);
    glfwInit( );

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    GLFWwindow* window = glfwCreateWindow(512, 512, "Tetris 1", nullptr, nullptr);
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    GLenum status = glewInit( );

    if (status != GLEW_OK) {
        std::cerr << "Error: " << glewGetErrorString(status) << std::endl;
        return 1;
    }

    GLuint shaderProgram = linkShaderProgram("vertex_shader.glsl", "fragment_shader.glsl");

    glViewport(0, 0, 512, 512);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    GLfloat scale = 0.1;

    GLfloat I[8] = { 1.0f, 0.0f,    0.0f,  0.0f,   -1.0f,  0.0f,     2.0f,  0.0f };
    GLfloat O[8] = { 0.0f, 0.0f,   -1.0f,  0.0f,   -1.0f, -1.0f,     0.0f, -1.0f };
    GLfloat Z[8] = { 0.0f, 0.0f,    1.0f,  0.0f,    1.0f, -1.0f,     2.0f, -1.0f };
    GLfloat T[8] = { 0.0f, 0.0f,    1.0f,  0.0f,    0.0f, -1.0f,    -1.0f,  0.0f };
    GLfloat L[8] = { 0.0f, 0.0f,    0.0f, -1.0f,    0.0f, -2.0f,    -1.0f, -2.0f };

    GLuint vbo, ebo;
    GLuint figures[5][4];
    createFigure(figures[0], &vbo, &ebo, -5.0f,  4.0f, I);
    createFigure(figures[1], &vbo, &ebo, -4.0f, -4.0f, O);
    createFigure(figures[2], &vbo, &ebo,  0.0f,  0.0f, Z);
    createFigure(figures[3], &vbo, &ebo,  5.0f,  4.0f, T);
    createFigure(figures[4], &vbo, &ebo,  4.0f, -4.0f, L);

    for (; !glfwWindowShouldClose(window); glfwSwapBuffers(window)) {
        glfwPollEvents( );
        glClear(GL_COLOR_BUFFER_BIT);

        GLint location = glGetUniformLocation(shaderProgram, "scale");
        glUniform1f(location, scale);
        glUseProgram(shaderProgram);

        GLfloat color[4] = { 0.0f, 0.0f, 0.0f, 1.0f };
        for (GLint i = 0; i < 5; ++i) {
            color[i % 3] = (color[i % 3] >= 0.5 ? 0.0f : 1.0f);
            for (GLint j = 0; j < 4; ++j) {
                change_tone(color, j % 2);
                GLint location_t = glGetUniformLocation(shaderProgram, "color");
                glUniform4f(location_t, color[0], color[1], color[2], color[3]);
                glBindVertexArray(figures[i][j]);
                glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, (GLvoid*)0);
                glBindVertexArray(0);
            }
        }
    }

    glDeleteBuffers(1, &vbo);
    glDeleteBuffers(1, &ebo);

    for (GLint i = 0; i < 5; ++i) {
        glDeleteVertexArrays(4, figures[i]);
    }

    glfwTerminate( );
}

void error_callback(GLint error, const GLchar* description) {
    std::cerr << "Error " << error << ": " << description << std::endl;
    std::cin.get();
    exit(1);
}

GLuint createSqrt(GLuint* vbo, GLuint* ebo, GLfloat dx, GLfloat dy) {
    GLfloat vertex[] = {
        -0.5f, -0.5f,
         0.5f, -0.5f,
        -0.5f,  0.5f,
         0.5f,  0.5f,
    };

    for (GLint i = 0; i < 4; ++i) {
        vertex[2 * i + 0] += dx;
        vertex[2 * i + 1] += dy;
    }

    GLuint elements[] = {
        0, 1, 2,
        1, 3, 2,
    };

    GLuint vao;

    glGenVertexArrays(1, &vao);
    glGenBuffers(1, vbo);
    glGenBuffers(1, ebo);

    glBindVertexArray(vao);

    glBindBuffer(GL_ARRAY_BUFFER, *vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glBindVertexArray(0);
    return vao;
}

void createFigure(GLuint figures[4], GLuint* vbo, GLuint* ebo, GLint x, GLint y, GLfloat d[8]) {
    for (GLint i = 0; i < 4; ++i) {
        figures[i] = createSqrt(vbo, ebo, d[i * 2 + 0] + x, d[i * 2 + 1] + y);
    }
}

void change_tone(GLfloat color[4], GLint op) {
    for (GLint i = 0; i < 3; ++i) {
        color[i] = (color[i] >= 0.5f ? 1.0f - (op ? 0.0f : 0.2f) : 0.0f);
    }
}