我正在尝试用OpenGL来画线。当我点击鼠标左键时，它会得到第一个坐标。然后当我移动鼠标时，第二个坐标同时也是我的鼠标坐标。第二个坐标要等到我点击右键后才能确定。
但我的代码有两个问题：
1.似乎当我甚至没有点击我的左按钮，有线在屏幕上。
1.我无法通过单击右键确定第二个坐标。
下面是我的代码：

# include<GLUT/GLUT.h>

# include<stdlib.h>

# include<stdio.h>

# include<math.h>

# include<time.h>

int m0,n0,m1,n1,ww,hh;
int flag=0;

void DrawPoint(int x,int y){
    glBegin(GL_POINTS);
        glVertex2f(x,y);
    glEnd();
}
void BresenhamLine(int x1,int y1,int x2,int y2){
    int x,y,delta1,delta2,e;
    delta1=x2-x1;
    delta2=y2-y1;
    int flag=0;
    x=x1;
    y=y1;
    if (abs(delta2)>abs(delta1)){
        flag=1;
    }

    int t1=(x2>x1?1:(delta1=-delta1,-1));
    int t2=(y2>y1?1:(delta2=-delta2,-1));
    glBegin(GL_POINTS);
    glColor3f(0.0,1.0,0.0);
    glVertex2f(x,y);
    if(flag==0){
        e=-delta1;
        while(x!=x2){
            x+=t1;
            e+=2*delta2;
            if(e>=0)
            {
                y+=t2;
                e-=2*delta1;
            }
            glVertex2f(x,y);
        }
    }
    else{
        e=-delta2;
        while(y!=y2)
        {
            y+=t2;
            e+=2*delta1;
            if(e>=0)
            {
                x+=t1;
                e-=2*delta2;
            }
            glVertex2f(x,y);
        }
    }
    glEnd();
    glFlush();
}
void DrawLine(){
    //bresenhamline
    BresenhamLine(m0,n0,m1,n1);
    glFlush();
}
void myreshape(GLint w,GLint h)
{
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0,(GLfloat)w,0,(GLfloat)h);
    glMatrixMode(GL_MODELVIEW);
    ww=w;
    hh=h;
}

void mymouse(int button,int state,int x,int y){

    if(state==GLUT_DOWN && button == GLUT_LEFT_BUTTON){
        m0=x;
        n0=hh-y;

    }

    if(state == GLUT_DOWN && button == GLUT_RIGHT_BUTTON){
        m1=x;
        n1=hh-y;
        glutPostRedisplay();
    }
}

void mymotion(int x,int y){
    m1=x;
    n1=hh-y;
    glutPostRedisplay();
}

void init(){
    glClearColor(1,1,1,1);
    glPointSize(3.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, 500,500, 0);
}

void mydisplay(){
    glClear(GL_COLOR_BUFFER_BIT);
    DrawLine();
    glFlush();
}
int main(int argc,char**argv){
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(0,0);
    glutCreateWindow("simple");
    glutDisplayFunc(mydisplay);
    glutMouseFunc(mymouse);
    glutReshapeFunc(myreshape);
    glutPassiveMotionFunc(mymotion);
    glutMainLoop();
}