通过右键单击完成绘制多边形，但显示菜单

Question

我正在编写一个程序，该程序将连续绘制多边形，直到用户右键单击为止。用户只能在当且仅当用户在菜单中做出选择时进行绘制，如果用户没有在菜单中作出选择，程序将不会绘制。到目前为止，我的程序已经成功地用鼠标绘制了一个多边形，但问题是，当我右键单击完成时，程序会弹出菜单，而不是完成多边形。现在我如何右键点击才能完成多边形，下面是我的程序：

const int MAX = 100;
float mouseX, mouseY, ListX[MAX], ListY[MAX];
int numPoints = 0, closed = 0, shape = 0;
void mouse(int button, int state, int x, int y)
{
    mouseX = x;
    mouseY = y;
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        if (closed || numPoints >= MAX - 1)
            numPoints = 0;
        closed = 0;
        ListX[numPoints] = mouseX;
        ListY[numPoints] = mouseY;
        numPoints++;
    }
    if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
        closed = 1;
}
void motion(int x, int y)
{
    mouseX = x;
    mouseY = y;
    glutPostRedisplay();
}
void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    if (shape == 1)
    {
        if (numPoints)
        {
            glBegin(GL_LINE_STRIP);
            for (int i = 0; i < numPoints; ++i)
                glVertex2f(ListX[i], ListY[i]);
            if (closed)
                glVertex2f(ListX[0], ListY[0]);
            else
                glVertex2f(mouseX, mouseY);
            glEnd();
        }
    }
    glFlush();
}
void menu(int choice)
{
    switch (choice)
    {
    case 1:
        shape = 1;
        break;
    }
}
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("");
    gluOrtho2D(0, 640, 480, 0);
    glutCreateMenu(menu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(motion);
    
    glutMainLoop();
}

编辑：感谢genpfault，我通过右键单击完成了多边形，但我不知道如何重新附加它，以便重新打开菜单。

...
void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    if (shape == 1)
    {
        glutDetachMenu(GLUT_RIGHT_BUTTON); // Add this
        ...
    }
    glFlush();
}
void menu(int choice)
{
    switch (choice)
    {
    case 1:
        shape = 1;
        break;
    }
}
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("");
    gluOrtho2D(0, 640, 480, 0);
    glutCreateMenu(menu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(mouse_move);
    glutMainLoop();
}

Answer 1

1. 捕获glutCreateMenu()的返回值，这是新菜单的句柄
2. 通过CCD_ 2分离菜单回调中的菜单，并设置一个bool；添加点"；模式
3. 如果你在"；添加点"；模式并检测到右键单击，通过glutSetMenu()将当前菜单设置为#1的菜单句柄，然后用glutAttachMenu()重新附加菜单。重置"；添加点"；bool到CCD_ 5

全部：

#include <GL/glut.h>
const int MAX = 100;
float mouseX, mouseY, ListX[MAX], ListY[MAX];
int numPoints = 0, closed = 0, shape = 0;
int hMenu = 0;
bool addingPoints = false;
void mouse(int button, int state, int x, int y)
{
    mouseX = x;
    mouseY = y;
    if( addingPoints )
    {
        if( button == GLUT_LEFT_BUTTON && state == GLUT_DOWN )
        {
            if (closed || numPoints >= MAX - 1)
                numPoints = 0;
            closed = 0;
            ListX[numPoints] = mouseX;
            ListY[numPoints] = mouseY;
            numPoints++;
        }
        if( button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN )
        {
            closed = 1;
            addingPoints = false;
            glutSetMenu(hMenu);
            glutAttachMenu(GLUT_RIGHT_BUTTON);
        }
    }
}
void motion(int x, int y)
{
    mouseX = x;
    mouseY = y;
    glutPostRedisplay();
}
void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, 640, 480, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    if (shape == 1)
    {
        if (numPoints)
        {
            glBegin(GL_LINE_STRIP);
            for (int i = 0; i < numPoints; ++i)
                glVertex2f(ListX[i], ListY[i]);
            if (closed)
                glVertex2f(ListX[0], ListY[0]);
            else
                glVertex2f(mouseX, mouseY);
            glEnd();
        }
    }
    glutSwapBuffers();
}
void menu(int choice)
{
    switch (choice)
    {
    case 1:
        numPoints = 0;
        shape = 1;
        addingPoints = true;
        glutDetachMenu(GLUT_RIGHT_BUTTON);
        break;
    }
}
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutCreateWindow("");
    hMenu = glutCreateMenu(menu);
    glutSetMenu(hMenu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(motion);
    glutMainLoop();
}