c++ - XGrabKeyboard 仅在程序运行时阻止键盘

Question

我正在编写代码来获取按下的键并阻止键盘输入。示例:如果按下 Super_L 或 Super_R 键，阻止它们打开应用程序菜单。该代码在程序打开时有效，但当程序关闭时， key 将发送到系统。示例:如果用户在程序运行时按下 Super_L 键，则不会发生任何事情，但当程序关闭时，会自动打开 Ubuntu 应用程序菜单。我该如何解决这个问题？

void hook()
{
    Display *dpy = XOpenDisplay(0);
    XEvent ev;

    if(!dpy)
    {
        qDebug() << "Error";
        return;
    }

    XGrabKeyboard(dpy, DefaultRootWindow(dpy), false, GrabModeAsync, GrabModeAsync, CurrentTime);

    forever
    {
        XNextEvent(dpy, &ev);
        switch (ev.type)
        {
        case KeyPress:
            qDebug() << "KeyPress" << XKeysymToString(XKeycodeToKeysym(dpy, ev.xkey.keycode, 0));
            break;
        case KeyRelease:
            qDebug() << "KeyRelease" << XKeysymToString(XKeycodeToKeysym(dpy, ev.xkey.keycode, 0));
            break;
        }
    }
}

Answer 1

引用the manual :

When the X server's connection to a client is closed either by an explicit call to XCloseDisplay() or by a process that exits, the X server performs the following automatic operations:

• It disowns all selections owned by the client (see XSetSelectionOwner()).
• It performs an XUngrabPointer() and XUngrabKeyboard() if the client has actively grabbed the pointer or the keyboard.
• It performs an XUngrabServer() if the client has grabbed the server.
• It releases all passive grabs made by the client.

抓取是由客户请求并授予客户的。在抓取期间，所有相关事件都会传递给抓取客户端。没有客户，就没有抢夺。

我不知道这里有什么需要修复的。如果您希望某项功能正常工作，请确保实现该功能的应用程序正在运行。