鼠标拖动OpenGL/GLUT中的对象 [英] Mouse-drag object in OpenGL/GLUT

问题描述

我整天都在寻找一个简单程序的教程或示例代码-单击对象(例如2d矩形)，然后在按住并移动鼠标时，对象跟随鼠标，然后在释放鼠标时对象保留在新位置.换句话说，我想了解如何通过鼠标事件来拖放对象.

I have been searching all day for a tutorial or example code for a simple program - click on object (like a 2d rectangle for example) then as you hold and move the mouse the object follows the mouse, then on mouse release the object remains in new location. In other words, I want to understand how to drag and drop an object with the mouse events.

有人可以帮我指出与该问题有关的任何有用信息的正确方向吗?

Could anyone help to point me in the right direction of any useful sources of information relating to this problem?

推荐答案

感谢到目前为止的所有答复.

Thanks for all the responses so far.

我已经找到了解决方法，所以我将继续回答我自己的问题.

I have worked out how to do it, so I will go ahead an answer my own question.

我正在使用GLUT作为鼠标处理程序:

I am using GLUT as a mouse handler:

1. 单击鼠标并移动(glutMotionFunc)时，将调用拖动功能.

1. When the mouse is clicked and moving (glutMotionFunc) the drag function is called.

在拖动功能中，鼠标坐标(x，y)被转换为Points结构，同时被转换为窗口坐标.

In the drag function the mouse coordinates (x,y) are converted to a Points struct while being converted into window coordinates.

如果鼠标位于正方形内，则通过更改其坐标拖动正方形并重新显示.

If the mouse is within the square then drag the square by changing it's coordinates and redisplay.

我对OpenGL和C ++还是很陌生，所以我为乱码表示歉意.通过这种方式进行绘制时，我有点沮丧，因为重新绘制的正方形看上去使光标捕捉到了中心.为了学习的目的，我欢迎对此问题的替代解决方案和对我的代码的批评.

I am still very new to OpenGL and C++ so I do apologize for the messy coding. I am a bit frustrated in doing it this way as the redrawn square makes it seem the cursor snaps to the center. I welcome alternative solutions to this problem and criticism of my code, for learning purposes.

代码(包含glut并使用命名空间std):

CODE (included glut and using namespace std):

// points structure made of two coordinates; x and y
struct Points
{
    float x,y;  // initializor
    Points() { x = 0.0; y = 0.0; } // constructor

    Points(float _x, float _y) : x(_x), y(_y) {}
};

// square made of 4 points
class Square
{
public:
    Points pts[4]; // square structure
    Square(); // initialize constructor

    void draw(Square *sqr); // draw square
    Points mouse(int x, int y); // get mouse coordintaes
    Square* drag(Square *sqr, Points *mouse); // change points of sqr
};

// square constructor
Square::Square()
{
    pts[0] = Points(0.2,0.2);
    pts[1] = Points(0.4,0.2);
    pts[2] = Points(0.4,0.4);
    pts[3] = Points(0.2,0.4);
};

// draw function
void Square::draw(Square *sqr)
{
    // draw square fill
    int i;
    glColor3f(0.2, 0.2, 0.2);
    glBegin(GL_QUADS);
    for (i = 0; i < 4; ++i)
    {
        glVertex2f(sqr->pts[i].x, sqr->pts[i].y);
    }
    glEnd();
    // draw square points
    i = 0;

    glColor3f(1.0, 1.0, 1.0);
    glBegin(GL_POINTS);
    for (i = 0; i < 4; ++i)
    {
        glVertex2f(sqr->pts[i].x, sqr->pts[i].y);
    }
    glEnd();
}

// mouse function
Points Square::mouse(int x, int y)
{
    int windowWidth = 400, windowHeight = 400;
    return Points(float(x)/windowWidth, 1.0 - float(y)/windowHeight);
}

// drag function
Square* Square::drag(Square *sqr, Points *mouse)
{
    sqr->pts[0].x = mouse->x - 0.1;
    sqr->pts[0].y = mouse->y - 0.1;
    sqr->pts[1].x = mouse->x + 0.1;
    sqr->pts[1].y = mouse->y - 0.1;

    sqr->pts[3].x = mouse->x - 0.1;
    sqr->pts[3].y = mouse->y + 0.1;

    sqr->pts[2].x = mouse->x + 0.1;
    sqr->pts[2].y = mouse->y + 0.1;

    return sqr;
}

// GLOBAL

// create square object
Square* sqr = new Square;


// display at start
void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    sqr->draw(sqr);
    glFlush();
}

// drag function
void drag (int x, int y)
{
    // int x and y of mouse converts to screen coordinates
    // returns the point as mousePt
    Points mousePt = sqr->mouse(x,y);
    //create pointer to window point coordinates
    Points* mouse = &mousePt;

    // if the mouse is within the square
    if (mouse->x > sqr->pts[0].x && mouse->y > sqr->pts[0].y)
    {       
        if (mouse->x < sqr->pts[2].x && mouse->y < sqr->pts[2].y)
        {
            // then drag by chaning square coordinates relative to mouse
            sqr->drag(sqr,mouse);
            glutPostRedisplay();
        }
    }
}


void Initialize() {
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

int main(int iArgc, char** cppArgv) {

    glutInit(&iArgc, cppArgv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(400, 400);
    glutInitWindowPosition(200, 200);
    glutCreateWindow("Move Box");


    glutMotionFunc(drag);

    Initialize();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

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