#include <GL/glut.h>

GLdouble winHeight;


GLsizei winWidth =400, winheight=300;
GLint endPTCtr=0;

class scrPt{
      public:
      GLint x,y;
      };
      void init(void)
      {
           glClearColor (0.0, 0.0, 1.0,1.0);
           glMatrixMode(GL_PROJECTION);
           gluOrtho2D (0.0, 200.0, 0.0,150.0);
           }
           
           void displayFcn(void)
           {
                glClear(GL_COLOR_BUFFER_BIT);
                }
                
      void winReshapeFcn (GLint newWidth, GLint newHeight)
      {
           /*reset viewport parameters*/
           glViewport (0, 0, newWidth,newHeight);
           glMatrixMode(GL_PROJECTION);
           glLoadIdentity();
           gluOrtho2D (0.0, GLdouble (newWidth), 0.0, GLdouble (newHeight));
           
           /* reset dspaly window*/
           winWidth =  newWidth;
            winHeight = newHeight;
           }
           
      void drawLineSegment (scrPt endPt1,scrPt endPt2)
      {
           glBegin (GL_LINES);
           glVertex2i(endPt1.x, endPt1.y);
            glVertex2i(endPt2.x, endPt2.y);
          glEnd();
          }
          
          void polyline (GLint button, GLint action, GLint xMouse, GLint yMouse)
          {
               static scrPt endPt1, endPt2;
               int ptCtr;
               if(ptCtr == 0){
                if(button== GLUT_LEFT_BUTTON && action == GLUT_DOWN) {
                  endPt1.x= xMouse;
                  endPt1.y= (GLint)(winHeight - yMouse);
                  ptCtr = 1;
                  }
                  else
                     if (button == GLUT_RIGHT_BUTTON)
                         exit(0);
                    }
                    else
                      if(button == GLUT_LEFT_BUTTON && action == GLUT_DOWN){
                               endPt2.x = xMouse;
                               endPt2.x = (GLint)(winHeight- yMouse);
                               drawLineSegment (endPt1, endPt2);
                               
                               endPt1 = endPt2;
                               
                      }
                      else
                        if (button == GLUT_RIGHT_BUTTON)
                          exit(0);
                                   
                               glFlush();
                          }
                          
         int main (int argc, char** argv)
          {
               glutInit (&argc,argv);
               glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
               glutInitWindowPosition (100,100);
               glutInitWindowSize (winWidth,winHeight);
               glutCreateWindow ("draw");
               init();
               glutDisplayFunc(displayFcn);
               glutReshapeFunc(winReshapeFcn);
               glutMouseFunc(polyline);
               
          glutMainLoop();
          }