/*  line.c    */

/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */


/* illustrates rubberband line drawing */

#include <GL/glut.h>int ww;float xm, ym, xmm, ymm;int first = 0;void init(){	glClearColor(1.0, 1.0, 0.0, 1.0);	glEnable(GL_COLOR_LOGIC_OP); 	glLogicOp(GL_COPY);}void display(){	glClear(GL_COLOR_BUFFER_BIT);	glColor3f(1.0, 0.0, 0.0);	glRectf(0.25, 0.25, 0.75, 0.75);	glLogicOp(GL_XOR);	glColor3f(1.0, 1.0, 0.0);	glFlush();}void reshape(int w, int h){	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	gluOrtho2D (0.0,  1.0, 0.0,  1.0);	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();}void mouse(int btn, int state, int x, int y){	if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) 	{		switch(first)		{		case 0: 			xm = x/500.;			ym = (500-y)/500.;			first = 1;			break;		case 1:			xmm = x/500.0;			ymm = (500-y)/500.0;			glBegin(GL_LINES);				glVertex2f(xm, ym);				glVertex2f(xmm, ymm);			glEnd();			glFlush();			first = 2;			break;		case 2:			glBegin(GL_LINES);				glVertex2f(xm, ym);				glVertex2f(xmm, ymm);			glEnd();			glFlush();
			xmm = x/500.0;			ymm = (500-y)/500.0;			glBegin(GL_LINES);				glVertex2f(xm, ym);				glVertex2f(xmm, ymm);			glEnd();			glFlush();			break;		}	}	if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN) 	{		glLogicOp(GL_COPY);		glColor3f(0.0, 0.0, 1.0);		glBegin(GL_LINES);			glVertex2f(xm, ym);			glVertex2f(xmm, ymm);		glEnd();		glFlush();		first = 0;		glLogicOp(GL_XOR);		glColor3f(0.0, 1.0, 0.0);	}}int main(int argc, char** argv){/* Initialize mode and open a window in upper left corner of screen *//* Window title is name of program (arg[0]) */	glutInit(&argc,argv); 	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);	glutInitWindowSize(500,500);	glutInitWindowPosition(0,0); 	glutCreateWindow("rubberband");	glutDisplayFunc(display);	glutReshapeFunc(reshape);	glutMouseFunc(mouse);	init();	glutMainLoop();}