Drawpixels by glfw only renderer quarter screen. buffer use screen width * height - c++

Question

I don't know how to resolve this problem, I want to use this function to make a soft-renderer engine to study 3D pipeline.
This is code:
#define GLFW_INCLUDE_GLU
#include <GLFW/glfw3.h>
int main(int argc, const char * argv[]) {
if(!glfwInit()){ //init error
return -1;
}
int width = 200; //screen width
int height = 200; //screen height
GLFWwindow* window = glfwCreateWindow(width, height, "Hello OpenGL", NULL, NULL); //create window
if(!window){ //create window fail
glfwTerminate();
return -1;
}
u_char* pixels = new unsigned char[width * height * 4]; //buffer
uint index; //temp
//set pixel
for (int count_a = 0; count_a < width; count_a++) {
for (int count_b = 0; count_b < height; count_b++) {
index = count_b * width + count_a;
pixels[index * 4 + 0] = 255; //red pixel
pixels[index * 4 + 1] = 0; //green
pixels[index * 4 + 2] = 0; //blue
pixels[index * 4 + 3] = 255; //alpha
}
}
glfwMakeContextCurrent(window);
while (!glfwWindowShouldClose(window)) { //close window
glClearColor(1.0, 1.0, 1.0, 1.0); //clear screen by white pixel
glClear(GL_COLOR_BUFFER_BIT);
glRasterPos2f(-1, -1); //set origin to screen bottom left
//glPixelZoom(2, 2); //if i use this function. renderer is right.
glDrawPixels(width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels); //draw pixel
glfwSwapBuffers(window); //swap buffer
}
glfwTerminate();
return 0;
}

Answer 1

I was having this issue when using GLUT, so I came to this before and while reimplementing my code using GLFW. This issue is caused by the Retina display (as a lot of other sources have figured out), and the following ended up fixing it for me:
int width = 1360*2; //screen width
int height = 768*2; //screen height
GLFWwindow* window = glfwCreateWindow(width/2, height/2, "Hello OpenGL", NULL, NULL); //create window
// ...