Line Clipping or Liang Bersky Algorithm source code in c++ with openGL

#include <windows.h>

#include <GL/glut.h>

#include <stdlib.h>

#include <iostream>

#include <string>

#include <string>

#include <ctype.h>

#include <math.h>

#include <stdio.h>

#include <map>

#include <vector>



double xmin=50,ymin=50,xmax=100,ymax=100;

double xvmin=150,yvmin=150,xvmax=400,yvmax=400;

double x2,y2,x3,y3;



int test(double p,double q,double *t1,double *t2)

{

    double t=q/p;

    if(p<0.0)

    {

        if(t> *t1) *t1=t;

        if(t> *t2) return(false);

    }

    else if(p>0.0)

    {

        if(t< *t2) *t2=t;

        if(t< *t1) return(false);

    }

    else if(p==0.0)

    {

        if(q<0.0) return(false);

    }

    return(true);

}



void LiangBarsky(double x0,double y0,double x1,double y1)

{

    double dx=x1-x0,dy=y1-y0,te=0.0,tl=1.0;



    if(test(-dx,x0-xmin,&te,&tl))

    if(test(dx,xmax-x0,&te,&tl))

    if(test(-dy,y0-ymin,&te,&tl))

    if(test(dy,ymax-y0,&te,&tl))

    {

        if(tl<1.0){x1=x0+tl*dx;y1=y0+tl*dy;}

        if(te>0.0){x0=x0+te*dx;y0=y0+te*dy;}



        double sx=(xvmax-xvmin)/(xmax-xmin);

        double sy=(yvmax-yvmin)/(ymax-ymin);



        double vx0=xvmin+(x0-xmin)*sx;

        double vy0=yvmin+(y0-ymin)*sy;

        double vx1=xvmin+(x1-xmin)*sx;

        double vy1=yvmin+(y1-ymin)*sy;



        glColor3f(1.0,0.0,0.0);

        glBegin(GL_LINE_LOOP);

        glVertex2f(xvmin,yvmin);

        glVertex2f(xvmax,yvmin);

        glVertex2f(xvmax,yvmax);

        glVertex2f(xvmin,yvmax);

        glEnd();

        glColor3f(0.0,0.0,1.0);

        glBegin(GL_LINES);

        glVertex2d(vx0,vy0);

        glVertex2d(vx1,vy1);

        glEnd();

     }

}



/*

 Robel Sharma

*/

void display()

{

    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(1.0,0.0,0.0);

    glBegin(GL_LINES);

    glVertex2d(x2,y2);

    glVertex2d(x3,y3);

    glEnd();

    glColor3f(0.0,0.0,1.0);

    glBegin(GL_LINE_LOOP);

    glVertex2f(xmin,ymin);

    glVertex2f(xmax,ymin);

    glVertex2f(xmax,ymax);

    glVertex2f(xmin,ymax);

    glEnd();

    LiangBarsky(x2,y2,x3,y3);

    glFlush();

}



void myinit()

{

    glClearColor(1.0,1.0,1.0,1.0);

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluOrtho2D(0.0,499.0,0.0,499.0);

}



int main(int argc, char *argv[])

{



    printf("Enter the end points of the line: ");

    scanf("%lf%lf%lf%lf", &x2,&y2,&x3,&y3);

    glutInit(&argc,argv);

    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);

    glutInitWindowSize(600,600);

    glutInitWindowPosition(0,0);

    glutCreateWindow("Line Clipping");

    glutDisplayFunc(display);

    myinit();

    glutMainLoop();

}