OpenGL white window while code runs glew/glfw3

Question

So I am trying to draw two triangles, but at the end I just get the white window without any triangles. I have set up the libraries correctly but I believe there could be a mistake somewhere in the code and since I am fairly new I cannot figure it out. The code complies with no errors or warnings, but the outcome is not what I have expected the window is white and there is no drawing shown in the window.

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


#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600

int main(void)
{
    GLFWwindow* window;
    // initialize the library
    if (!glfwInit())
    {
        return -1;
    }
    // Create a window and its context
    window = glfwCreateWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "kk", NULL, NULL);

    int screenWidth, screenHeight;
    glfwGetFramebufferSize(window, &screenWidth, &screenHeight);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    // make the window's context current
    glfwMakeContextCurrent(window);

    glViewport(0, 0, screenWidth, screenHeight); //specifies part of the window OpenGL can draw on
    glMatrixMode(GL_PROJECTION); //controls the camera
    glLoadIdentity(); //put us at (0, 0, 0)
    glOrtho(0, SCREEN_WIDTH, 0, SCREEN_HEIGHT, 0, 600); //cordinate system
    glMatrixMode(GL_MODELVIEW); //defines how objects are trasformed
    glLoadIdentity(); //put us at (0, 0, 0)

    GLfloat first_triangle[] = {
        0, 0, 0,
        0,300,0,
        200,300,0,
    };

    GLfloat second_triangle[] = {
        200,300,0,
        400,300,0,
        400,600,0,
    };
    GLfloat color[] =
    {
        255,0,0,
        0,255,0,
        0,0,255
    };
    // Loop until the window is closed by the user
    while (!glfwWindowShouldClose(window))
    {
        glClear(GL_COLOR_BUFFER_BIT);
        //OpenGL rendering
        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_COLOR_ARRAY);

        glVertexPointer(3, GL_FLOAT, 0, first_triangle); // points to the vertices to be used
        glColorPointer(3, GL_FLOAT, 0, color); // color to be used
        glDrawArrays(GL_TRIANGLES, 0, 3); // draw the vetices
        glVertexPointer(3, GL_FLOAT, 0, second_triangle); // points to the vertices to be used
        glColorPointer(3, GL_FLOAT, 0, color); // color to be used
        glDrawArrays(GL_TRIANGLES, 0, 3);

        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_VERTEX_ARRAY);
    };
    
}

Answer 1

You have to call glfwSwapBuffers and glfwPollEvents at the end of the application loop:

while (!glfwWindowShouldClose(window))
{
    // [...]

    glfwSwapBuffers(window);
    glfwPollEvents();
}

glfwSwapBuffers swaps the front and back buffers and causes the window to be updated.
glfwPollEvents process the events.