用opengl编写一个简单的画图软件示例代码

//用opengl编写一个简单的画图软件示例代码（存在闪烁问题）
//本代码，抄写自一本教授opengl的书，可惜，里面的代码存在一些问题，导致不能正常显示，现在是增加了一些语句的代码
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gl/glut.h>
#include <GL/gl.h>

#define  NULL 0
#define  LINE 1
#define RECTANGLE 2
#define TRIANGLE 3
#define POINTS 4
#define  TEXT 5
void mouse(int,int,int,int);
void key(unsigned char,int,int);
void display(void);
void drawSquare(int,int);
void myReshape(GLsizei,GLsizei);
void myinit(void);
void screen_box(int,int,int);
void right_menu(int);
void middle_menu(int);
void color_menu(int);
void pixel_menu(int);
void fill_menu(int);
int pick(int,int);
/////
long time(int);
long baset;
/////
GLsizei wh=500,ww=500;
GLfloat size=3.0;
int draw_mode=0;
int rx,ry;
GLfloat r=1.0,g=1.0,b=1.0;
int fill=0;
void drawSquare(int x,int y)
{
 y=wh-y;
 glColor3ub((char)rand()%256,(char)rand()%256,(char)rand()%256);
 glBegin(GL_POLYGON);
   glVertex2f(x+size,y+size);
   glVertex2f(x-size,y+size);
   glVertex2f(x-size,y-size);
   glVertex2f(x+size,y-size);
 glEnd();
}
void myReshape(GLsizei w,GLsizei h)
{
 glMatrixMode(GL_PROJECTION);//模式
 glLoadIdentity();
 glOrtho(0.0,(GLdouble)w,0.0,(GLdouble)h,-1.0,1.0);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
 glViewport(0,0,w,h);
 glClearColor(0.8,0.8,0.8,1.0);
 glClear(GL_COLOR_BUFFER_BIT);
 display();
 glFlush();
 ww=w;
 wh=h;
}
void myinit(void)
{
    glViewport(0,0,ww,wh);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0,(GLdouble)ww,0.0,(GLdouble)wh,-1.0,1.0);
    glClearColor(0.8,0.8,0.8,1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glFlush();
}
void mouse(int btn,int state,int x,int y)
{
  static int count;
  int where;
  static int xp[2],yp[2];
  if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
  {
   glPushAttrib(GL_ALL_ATTRIB_BITS);
   where=pick(x,y);
   glColor3f(r,g,b);
   if(where!=0)
   {
    count=0;
    draw_mode=where;
   }
   else switch(draw_mode)
   {
    case (LINE):
        if(count=0)
        {
         count++;
         xp[0]=x;
         yp[0]=y;
        }
        else
        {
         glBegin(GL_LINES);
         glVertex2i(x,wh-y);
         glVertex2i(xp[0],wh-yp[0]);
         glEnd();
         draw_mode=0;
         count=0;
        }
        break;
        case(RECTANGLE):
        if(count=0)
        {
         count++;
         xp[0]=x;
         yp[0]=y;
        }
        else
        {
            if(fill)
             glBegin(GL_POLYGON);
            else
             glBegin(GL_LINE_LOOP);
             glVertex2i(x,wh-y);
             glVertex2i(xp[0],wh-yp[0]);
             glVertex2i(xp[0],wh-yp[0]);
             glVertex2i(xp[0],wh-y);
             glEnd();
         draw_mode=0;
         count=0;
        }
        break;
        case(TRIANGLE):
        switch(count)
        {
         case (0):
           count++;
           xp[0]=x;
           yp[0]=y;
           break;
         case (1):
             count++;
             xp[1]=x;
             yp[1]=y;
             break;
         case (2):
             if(fill)
             glBegin(GL_POLYGON);
            else
             glBegin(GL_LINE_LOOP);
             glVertex2i(xp[0],wh-yp[0]);
             glVertex2i(xp[1],wh-yp[1]);
             glVertex2i(x,wh-y);
             glEnd();
         draw_mode=0;
         count=0;
        }       
        break;
        case(POINTS):   
        {
         drawSquare(x,y);
         count++;
        }
        break;
        case(TEXT):
        {
         rx=x;
         ry=wh-y;
         glRasterPos2i(rx,ry);
         count=0;
        }
       
   }
   glPopAttrib();
   glFlush();
  }
}
int pick(int x,int y)
{
 y=wh-y;
 if(y<wh-ww/10)
     return 0;
 else if(x<ww/10) return LINE;
 else if(x<ww/5) return RECTANGLE;
 else if(x<3*ww/10) return TRIANGLE;
 else if(x<2*ww/5) return POINTS;
 else if(x<ww/2) return TEXT;
 else  return 0;
}
void screen_box(int x,int y,int s)
{
 glBegin(GL_QUADS);
 glVertex2i(x,y);
 glVertex2i(x+s,y);
 glVertex2i(x+s,y+s);
 glVertex2i(x,y+s);
 glEnd();
}
//////************
void idle(void)
{
char out[]="00:00:00";
long t,time(int a);
int min, sec, hr;
 glPushAttrib(GL_ALL_ATTRIB_BITS);
 
 t = 5623;
 hr=t/3600;
 min = (t - 3600*hr) /60;
 sec = (t - 3600*hr - 60*min);
 hr = hr%24;
 out[0]='0'+hr/10;
 out[1]='0'+hr%10;
 out[3]='0'+min/10;
 out[4]='0'+min%10;
 out[6]='0'+sec/10;
 out[7]='0'+sec%10;
 glRasterPos2i(ww-80, wh-15);
 glColor3f(0.9 ,1.0 ,1.0);
 glBegin(GL_QUADS);
 glVertex2i(ww-80, wh-15);
 glVertex2i(ww, wh-15);
 glVertex2i(ww, wh);
 glVertex2i(ww-80, wh);
 glEnd();
 glColor3f(1.0,1.0,1.0);
 glCallLists(strlen(out) , GL_BYTE, out);
 glutSwapBuffers();
 glPopAttrib();
}
/////*************
void right_menu(int id)
{
 if(id==1) exit(0);
 else display();
}
void middle_menu(int id)
{
 
}
void color_menu(int id)
{
    if(id==1) {r=1;g=0;b=0;}
    else if(id==2) {r=0;g=1;b=0;}
    else if(id==3) {r=0;g=0;b=1;}
    else if(id==4) {r=0;g=1;b=1;}
    else if(id==5) {r=1;g=0;b=1;}
    else if(id==6) {r=1;g=1;b=0;}
    else if(id==7) {r=1;g=1;b=1;}
    else if(id==8) {r=0;g=0;b=0;}
}
void pixel_menu(int id)
{
 if(id==1) size=2*size;
 else if(size>1)
     size=size/2;
}
void fill_menu(int id)
{
     if(id==1) fill=1;
     else
     fill=0;
}
void key(unsigned char k,int xx,int yy)
{
 if(draw_mode!=TEXT)
     return;
 glColor3f(0.0,0.0,0.0);
 glRasterPos2i(rx,ry);
 glutBitmapCharacter(GLUT_BITMAP_9_BY_15,k);
 rx+=glutBitmapWidth(GLUT_BITMAP_9_BY_15,k);
}
void display(void)
{
 int shift=0;
 glPushAttrib(GL_ALL_ATTRIB_BITS);
 glClearColor(0.8,0.8,0.8,1.0);
 glClear(GL_COLOR_BUFFER_BIT);
 glColor3f(1.0,1.0,1.0);
 screen_box(0,wh-ww/10,ww/10);
 glColor3f(1.0,0,0);
 screen_box(ww/10,wh-ww/10,ww/10);
 glColor3f(1.0,0,0);
 screen_box(ww/5,wh-ww/10,ww/10);
 glColor3f(1.0,0,0);
 screen_box(3*ww/10,wh-ww/10,ww/10);
 glColor3f(1.0,1.0,0);
 screen_box(2*ww/5,wh-ww/10,ww/10);
 glColor3f(0,0,0);
 screen_box(ww/10+ww/40,wh-ww/10+ww/40,ww/20);
 glBegin(GL_LINES);
     glVertex2i(wh/40,wh-ww/20);
     glVertex2i(wh/40+ww/20,wh-ww/20);
 glEnd();
 glBegin(GL_TRIANGLES);
     glVertex2i(wh/5+ww/40,wh-ww/10+ww/40);
     glVertex2i(ww/5+ww/20,wh-ww/40);
     glVertex2i(ww/5+3*ww/40,wh-ww/20);
 glEnd();
 glPointSize(3.0);
 glBegin(GL_POINTS);
     glVertex2i(3*ww/10+ww/20,wh-ww/20);   
 glEnd();
 glRasterPos2i(2*ww/5,wh-ww/20);
 glutBitmapCharacter(GLUT_BITMAP_9_BY_15,'A');
 shift=glutBitmapWidth(GLUT_BITMAP_9_BY_15,'A');
 glRasterPos2i(2*ww/5+shift,wh-ww/20);
 glutBitmapCharacter(GLUT_BITMAP_9_BY_15,'B');
 shift+=glutBitmapWidth(GLUT_BITMAP_9_BY_15,'B');
 glRasterPos2i(2*ww/5+shift,wh-ww/20);
 glutBitmapCharacter(GLUT_BITMAP_9_BY_15,'C');
 glFlush();
 ///////****
 glutIdleFunc(idle);
 glutSwapBuffers();
 //////******
 glPopAttrib();
}

int main(int argc,char** argv)
{
 int c_menu,p_menu,f_menu;
 glutInit(&argc,argv);//初始化
 glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);//缓存模式
 glutInitWindowSize(500,500);//显示框大小
 //glutInitWindowPosition(50,50);
 glutCreateWindow("simpleCAD");
 glutDisplayFunc(display);
 c_menu=glutCreateMenu(color_menu);
 glutAddMenuEntry("Red",1);
 glutAddMenuEntry("Green",2);
 glutAddMenuEntry("Blue",3);
 glutAddMenuEntry("Cyan",4);
 glutAddMenuEntry("Magenta",5);
 glutAddMenuEntry("Yellow",6);
 glutAddMenuEntry("White",7);
 glutAddMenuEntry("Black",8);
 p_menu=glutCreateMenu(pixel_menu);
 glutAddMenuEntry("increase pixel size",1);
 glutAddMenuEntry("decrease pixel size",2);
 f_menu=glutCreateMenu(fill_menu);
 glutAddMenuEntry("fill on",1);
 glutAddMenuEntry("fill off",2);
 glutCreateMenu(right_menu);
 glutAddMenuEntry("quit",1);
 glutAddMenuEntry("clear",2);
 glutAttachMenu(GLUT_RIGHT_BUTTON);
 glutCreateMenu(middle_menu);
 glutAddSubMenu("Colors",c_menu);
 glutAddSubMenu("Pixel Size",p_menu);
 glutAddSubMenu("fill",f_menu);
 glutAttachMenu(GLUT_MIDDLE_BUTTON);
 myinit();
 glutReshapeFunc(myReshape);
 glutKeyboardFunc(key);
 glutMouseFunc(mouse);
 glutMainLoop();//进入glut事件处理循环
 return (0);
}