#include<stdio.h>
#include<conio.h>
#include<graphics.h>
#include<iostream.h>
#include<stdlib.h>
#include<math.h>

#definefalse 0
#definetrue  1

FILE *fin = fopen("cosuth.in","r");
float u1,u2,dx,dy;
float t1,t2,t3,t4,t5,t6;

class point
{
     int x,y;
     int code[4];
public:
    void getxy()
    {
        fscanf(fin,"%d %d",&x,&y);
    }
    void putxy(int x1,int y1)
    {
        x = x1;
        y = y1;
    }
    void friend clipline(point p1,point p2);
    int friend cliptest(float p,float q,float *u1,float *u2);
    void friend drawline(point p1,point p2);

}p1,p2,pt[20],winmin,winmax;

void clipline(point p1,point p2)
{
    rectangle(80,420,426,160);

    u1 = 0.0;
    u2 = 1.0;

    dx = p2.x - p1.x;
    t1 = p1.x - winmin.x;
    t2 = winmax.x - p1.x;
    t3 = p1.y - winmin.y;
    t4 = winmax.y - p1.y;
    t5 = -1 * dx;


    if (cliptest(t5,t1,&u1,&u2) == 1)
    {
        if (cliptest(dx,t2,&u1,&u2) == 1)
        {
            dy = float(p2.y - p1.y);
            t6 = -1 * dy;
            if (cliptest(t6,t3,&u1,&u2) == 1)
            {
                if (cliptest(dy,t4,&u1,&u2) == 1)
                {
                    if (u1 > 0.0)
                    {
                        (int)p1.x = p1.x + (u1 * dx);
                        (int)p1.y = p1.y + (u1 * dy);
                    }
                    if (u2 < 1.0)
                    {
                        (int)p2.x = p1.x + (u2 * dx);
                        (int)p2.y = p1.y + (u2 * dy);
                    }
                }
            }
        }
    }
    drawline(p1,p2);
    getch();
}

int cliptest(float p,float q,float *u1,float *u2)
{
    float r;
    int flag;

    flag = 1;

    if (p < 0.0)
    {
        r = (float) q / p;
        if (r > *u2)
        {
            flag = 0;
        }
        else
        {
            if (r > *u1)
            {
                *u1 = r;
            }
        }
    }
    else
    {
        if (p > 0.0)
        {
            r = (float) q / p;
            if (r < *u1)
            {
                flag = 0;
            }
            else
            {
                if (r < *u2)
                {
                    *u2 = r;
                }
            }
        }
        else
        {
            if (q < 0.0)
            {
                flag = 0;
            }
        }
    }
    return(flag);
}

void drawline(point p1,point p2)
{
     line(p1.x,p1.y,p2.x,p2.y);
}


void main()
{
    int drv=DETECT,mode,totalpoint,i;

    clrscr();

    printf("\nHow many line will be on the screen : ");
    fscanf(fin,"%d",&totalpoint);

    for(i = 0;i < totalpoint ; i++)
    {
        printf("\nEnter their x and y coordinates of %d point:\n",i+1);
        pt[i].getxy();
    }

    initgraph(&drv,&mode,"c:\\Borlandc\\bgi");
    winmin.putxy(80,160);
    winmax.putxy(420,426);
    rectangle(80,420,426,160);

    i = 0;

    do
    {
        drawline(pt[i],pt[i+1]);
        i++;
    }
    while(i < totalpoint-1);

    getch();
    clearviewport();

    i = 0;
    do
    {
        clipline(pt[i],pt[i+1]);
        i++;
    }
    while(i < totalpoint-1);
    getch();
}