glfw_triangle_no_vbo.c

/*
This is the most minimal possile example.

Seems deprecated:
https://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_02#Using_Vertex_Buffer_Objects_.28VBO.29_for_efficiency
Known as "client-side arrays".

Passes the array directly to the last argument of glVertexAttribPointer.
*/

#include "common.h"

static const GLuint WIDTH = 512;
static const GLuint HEIGHT = 512;
static const GLchar* vertex_shader_source =
    "#version 120\n"
    "attribute vec2 coord2d;\n"
    "void main(void) {\n"
    "    gl_Position = vec4(coord2d, 0.0, 1.0);\n"
    "}\n";
static const GLchar* fragment_shader_source =
    "#version 120\n"
    "void main(void) {\n"
    "    gl_FragColor.rgb = vec3(0.0, 0.0, 1.0);\n"
    "}\n";
static const GLfloat vertices[] = {
     0.0,  0.8,
    -0.8, -0.8,
     0.8, -0.8,
};

int main(void) {
    GLFWwindow *window;
    GLint attribute_coord2d, program;
    const char *attribute_name = "coord2d";

    /* Window system. */
    glfwInit();
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
    window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
    glfwMakeContextCurrent(window);
    glewInit();

    /* Shaders. */
    program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
    attribute_coord2d = glGetAttribLocation(program, attribute_name);

    /* Initial settings. */
    glUseProgram(program);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    glViewport(0, 0, WIDTH, HEIGHT);

    /* Main loop. */
    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();
        glClear(GL_COLOR_BUFFER_BIT);
        glEnableVertexAttribArray(attribute_coord2d);
        glVertexAttribPointer(
            attribute_coord2d,
            2,
            GL_FLOAT,
            GL_FALSE,
            0,
            vertices
        );
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glDisableVertexAttribArray(attribute_coord2d);
        glfwSwapBuffers(window);
    }

    /* Cleanup. */
    glDeleteProgram(program);
    glfwTerminate();
    return EXIT_SUCCESS;
}