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，它将连续绘制一个多边形，直到用户单击鼠标右键。只有当且仅当用户在菜单中进行选择时，用户才能绘制，如果用户未在菜单中进行选择，程序将不会绘制。到现在为止，我的程序已经用鼠标成功绘制了一个多边形，但是问题是当我右击完成时，程序弹出菜单，而不是完成多边形。现在我如何右键单击才能完成多边形，这是我的程序：

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

从 glutCreateMenu() 捕获 return 值，这是新菜单的句柄。
通过 glutDetachMenu() 在菜单回调中分离菜单并设置一个 bool 指示您处于“添加点”模式。
如果您处于“添加点”模式并检测到右键单击，请通过 glutSetMenu() 将当前菜单设置为 #1 中的菜单句柄，然后使用 [=14 重新附加菜单=].将“加分”布尔值重置为 false.

总计：

#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();
}

通过右键单击完成绘制多边形，但显示菜单

Finish drawing a polygon by right-clicking, but displaying a menu instead

c++

opengl

glut