OpenGL doesn't draw a point - c++

Question

OpenGL draws only the background, the yellow point does not appear. I want to draw it with glBegin and glEnd. The coordinates are variables, because I want to move that point later. Most of the code is just GLFW initialization the function that worries me is the
draw_player function since there the draw call is contained. The Fix I stumbled upon, to use GL_POINTS instead of GL_POINT (in glBegin as argument), does not help (I continue to use it though).
#include <GLFW/glfw3.h>
//#include <stdio.h>
//coordinates
int px, py;
//My not working function
void draw_player()
{
glColor3f(1.0f, 1.0f, 0);
glPointSize(64.0f);
glBegin(GL_POINTS);
glVertex2i(px, py);
glEnd();
}
int main(int argc, char* argv[])
{
GLFWwindow* window;
if (!glfwInit())
return -1;
window = glfwCreateWindow(910, 512, "Raycast", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glClearColor(0.1f, 0.1f, 0.5f, 1.0f);
//setting the coordinates
px = 100;
py = 10;
while (!glfwWindowShouldClose(window))
{
/* Render here */
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
draw_player();
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
}

Answer 1

The coordinate (100, 10) is not in the window. You have not specified a projection matrix. Therefore, you must specify the coordinates of the point in the normalized device space (in the range [-1.0, 1.0]).
If you want to specify the coordinates in pixel units, you must define a suitable orthographic projection with glOrtho:
int main(int argc, char* argv[])
{
GLFWwindow* window;
if (!glfwInit())
return -1;
window = glfwCreateWindow(910, 512, "Raycast", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glMatrixMode(GL_PROJECTION);
glOrtho(0, 910.0, 512.0, 0.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
// [...]
}