draw a line with open gl mouse function using dda/bresenham algorithm

Question

So i have to draw a line using mouse function. When the mouse clicks two points, the program needs to draw a line connecting them.

I need to make an imaginary 10x10 array and map the points on it and then connect the dots. window size doesn't matter.

I have no clue about what to do about the imaginary array and how to save the mouse coordinates so i can us them. Help

#include <glut.h>
#include<stdio.h>

void RenderScene(void) //점
{
    glClear(GL_COLOR_BUFFER_BIT);
    // Flush drawing commands
    glFlush();
}


void SetupRC(void) //바탕
{
    // setup clear color
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
}


void ChangeSize(GLsizei w, GLsizei h) {
        GLfloat  aspectRatio;
        // Prevent a divide by zero
        if (h == 0)
            h = 1;
        // Set Viewport to window dimensions
        glViewport(0, 0, w, h);
        // Reset coordinate system
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        // Establish clipping volume (left, right, bottom, top, near, far)
        aspectRatio = (GLfloat)w / (GLfloat)h;
        glOrtho(0, w, h, 0, 1.0, -1.0); 
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
}


void myRectf(GLfloat    x1, GLfloat     y1, GLfloat     x2, GLfloat     y2){
    glPointSize(10);

    ////ddaLine

    int dx, dy;
    int m = (y2 - y1) / (x2 - x1);
    for (int i = x1; i <= x2; i++)
    {
        if (m <= 1)
        {
            dx = 1;
            dy = m * dx;
        }
        else
        {
            dy = 1;
            dx = dy / m;
        }
        x1 += dx;
        y1 += dy;

        glBegin(GL_POINTS);
        glVertex3f(x1, y1, 0.f);
        glEnd();
    }

    /////breline
    while (x1 < x2)
    {
        int dx = x2 - x1;
        int dy = y2 - y1;
        int di = 2 * dy - dx;
        int ds = 2 * dy;
        int dt = 2 * (dy - dx);

        x1++;
        if (di < 0)
            di += ds;
        else
        {
            y1++;
            di += dt;
        }
        glBegin(GL_POINTS);
        glVertex3f(x1, y1, 0.f);
        glEnd();
    }
}

GLfloat g_x = -1000.f, g_y = -1000.f;

void MouseHandler(int button, int state, int x, int y){
    if (button == GLUT_LEFT_BUTTON
        && state == GLUT_DOWN){
        g_x = x; g_y = y;
        printf("%d,%d \n", x, y);
    }
    glutPostRedisplay();
}


void main(int argc, char* argv[]){
    int array[10][10];

    glutInit(&argc, argv); // initialize GL context
    // single or double buffering | RGBA color mode
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
    glutCreateWindow("Lec01");
    // callback function
    glutDisplayFunc(RenderScene);
    glutReshapeFunc(ChangeSize);

    SetupRC();          // initialize render context(RC)
    glutMouseFunc(MouseHandler);

    glutMainLoop();     // run GLUT framework
}

And I'm not allowed to use GL_LINES