OpenGL编程 基础篇（四）与鼠标的交互

当用户按下或释放鼠标按钮、按下按钮时移动鼠标或按下和松开键盘按键时，就会产生一个相关事件。程序员可以用每类事件注册一个回调函数，例如使用如下函数：

• glutMouseFunc(myMouse):利用按下或释放鼠标按钮时发生的事件来注册myMouse
• glutMotionFunc(myMovedMouse):利用按下按钮同时移动鼠标的事件来注册myMovedMouse
• glutKeyboardFunc(myKeyboard):利用按下和松开键盘按键的事件来注册myKeyboard

1.用鼠标交互

回调函数的名字可以随便起，但是一定要带4个参数，其原型如下：

void myMouse(int button,int state,int x,int y); 当鼠标事件发生时，系统会调用注册的函数，并向其提供这些参数值。

button的值可能是下面明显含义中的一个：GLUT_LEFT_BUTTON、GLUT_MIDDLE_BUTTON、GLUT_RIGHT_BUTTON

state 的值可能是：GLUT_UP、GLUT_DOWN

x和y的值指明事件发生时鼠标的位置（注意：x是距离窗口左边的像素数、y是距离窗口顶端的像素数）

时间处理器本身并不引起屏幕的重新绘制事件。因此，为了看到鼠标的效果，鼠标处理器应该调用glutPostRedisplay()

#include "stdafx.h"
#include <cstdlib>
#include <gl\glut.h>
const int screenWidth = 600;
const int screenHeight = 480;
class GLintPoint
{
public:
    GLint x;
    GLint y;
    GLintPoint(){
        x = 0; y = 0;
    }
    GLintPoint(GLint a, GLint b){
        x = a;
        y = b;
    }
};
void myInit(){
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glColor3f(0.0f, 0.0f, 0.0f);
    glPointSize(2.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble)screenWidth, 0.0, (GLdouble)screenHeight);
}

void drawDot(GLint x, GLint y){
    glBegin(GL_POINTS);
    glVertex2i(x, y);
    glEnd();
}
void myDisplay(GLintPoint corner[3]){　　//绘制Sierrapinski垫片的函数，参数为三个坐标点
    glClear(GL_COLOR_BUFFER_BIT);
    int index = rand() % 3;
    GLintPoint point = corner[index];
    drawDot(point.x, point.y);
    for (int i = 0; i < 55000; i++){
        index = rand() % 3;
        point.x = (point.x + corner[index].x) / 2;
        point.y = (point.y + corner[index].y) / 2;
        //printf("%d %d\n", point.x, point.y);
        drawDot(point.x, point.y);
    }
    glFlush();
}
//Simple One 用鼠标放置点，用户每次按下左键时，就会在屏幕窗口鼠标所在位置绘制出一个点；如果用户按下右键，就改变窗口背景颜色
void myMouse(int button, int state, int x, int y){
    if (state == GLUT_DOWN){
        if (button == GLUT_LEFT_BUTTON){
            drawDot(x, screenHeight - y);
            glFlush();
        }
        else if (button == GLUT_RIGHT_BUTTON){
            glClearColor(1.0f,0.0f,0.0f,0.0f);
            glClear(GL_COLOR_BUFFER_BIT);
            glFlush();
        }
    }
    return;
}
//Sierpinski 用鼠标控制Sierpinski垫片
void myMouseForSierpinski(int button, int state, int x, int y)
{

    static GLintPoint corner[3];
    static int numCorners = 0;
    if (state == GLUT_DOWN){
        if (button == GLUT_LEFT_BUTTON){
            corner[numCorners].x = x;
            corner[numCorners].y = screenHeight - y;
            if (++numCorners == 3){
                myDisplay(corner);
                numCorners = 0;
            }
        }
    }
    else if (button == GLUT_RIGHT_BUTTON){
        glClear(GL_COLOR_BUFFER_BIT);
        glFlush();
    }
}
void myDis(){}
int main(int argc, char **argv){

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(screenWidth, screenHeight);
    glutCreateWindow("Mouse Sierpinski");

    glutMouseFunc(myMouseForSierpinski);
    //glutMouseFunc(myMouse);
    glutDisplayFunc(myDis);
    myInit();
    glutMainLoop();
    return 0;
}