听取键盘事件，而不消耗他们在X11 - 键盘挂钩 [英] Listening to keyboard events without consuming them in X11 - Keyboard hooking

问题描述

我试图写一个程序，挂钩键盘消息，发出每个键的名称，每当它在Ubuntu（KDE）中按下;

I tried to write a program which hooks keyboard messages to pronounce the name of each key whenever it is pressed in Ubuntu (KDE); without interfering with normal action of keyboard in programs (just announcing the key name).

这是我的程序：

#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>

using namespace std;

void SendPressKeyEvent(Display *display, XKeyEvent xkey)
{
    Window current_focus_window;
    int current_focus_revert;
    XGetInputFocus(display, &current_focus_window, &current_focus_revert);
    xkey.type =  KeyPress;
    xkey.display = display;
    xkey.window = current_focus_window;
    xkey.root = DefaultRootWindow(display);
    xkey.subwindow = None;
    xkey.time = 1000 * time(0);
    xkey.x = 0;
    xkey.y = 0;
    xkey.x_root = 0;
    xkey.y_root = 0;
    xkey.same_screen = True;
    XSendEvent(display, InputFocus,  True, KeyPressMask, (XEvent *)(&xkey));
}

void SendReleaseKeyEvent(Display *display, XKeyEvent xkey)
{
    Window current_focus_window;
    int current_focus_revert;
    XGetInputFocus(display, &current_focus_window, &current_focus_revert);
    xkey.type =  KeyRelease;
    xkey.display = display;
    xkey.window = current_focus_window;
    xkey.root = DefaultRootWindow(display);
    xkey.subwindow = None;
    xkey.time = 1000 * time(0);
    xkey.x = 0;
    xkey.y = 0;
    xkey.x_root = 0;
    xkey.y_root = 0;
    xkey.same_screen = True;
    XSendEvent(display, InputFocus, True, KeyReleaseMask, (XEvent *)(&xkey));
}

void *TaskCode(void* arg)
{
    switch(*(int*)arg)
    {
    case 38:
        system("espeak -v en "  "\"a\"");
    }
    return 0;
}

int main()
{
    Display *display = XOpenDisplay(0);
    if(display == 0)
        exit(1);
    XGrabKeyboard(display, DefaultRootWindow(display), True, GrabModeAsync, GrabModeAsync, CurrentTime);
    XEvent event;
    while(true)
    {
        XNextEvent(display, &event);
        if(event.type == Expose)
        {

        }
        if(event.type == KeyPress)
        {
            SendPressKeyEvent(display,event.xkey);
            if(event.xkey.keycode == 38)
            {
                pthread_t thread;
                int thread_arg = event.xkey.keycode;
                pthread_create(&thread,0, TaskCode, (void*) &thread_arg);
            }
        }
        if(event.type == KeyRelease)
            SendReleaseKeyEvent(display,event.xkey);
    }
    XCloseDisplay(display);
}

此程式仅适用于键 a

但是当这个程序运行时，一些程序（如Chromium）不会在编辑框中显示闪光灯（光标）。所有KDE热键也将被禁用。

But when this program is running, some programs (e.g. Chromium) do not show the blinker (cursor) in their edit boxes. Also all KDE hotkeys become disabled.

如何解决这个问题？

推荐答案

这是我快速肮脏的例子

#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <stdio.h>
#include <ctype.h>


int main ()
{
    Display* d = XOpenDisplay(NULL);
    Window root = DefaultRootWindow(d);
    Window curFocus;
    char buf[17];
    KeySym ks;
    XComposeStatus comp;
    int len;
    int revert;

    XGetInputFocus (d, &curFocus, &revert);
    XSelectInput(d, curFocus, KeyPressMask|KeyReleaseMask|FocusChangeMask);

    while (1)
    {
        XEvent ev;
        XNextEvent(d, &ev);
        switch (ev.type)
        {
            case FocusOut:
                printf ("Focus changed!\n");
                printf ("Old focus is %d\n", (int)curFocus);
                if (curFocus != root)
                    XSelectInput(d, curFocus, 0);
                XGetInputFocus (d, &curFocus, &revert);
                printf ("New focus is %d\n", (int)curFocus);
                if (curFocus == PointerRoot)
                    curFocus = root;
                XSelectInput(d, curFocus, KeyPressMask|KeyReleaseMask|FocusChangeMask);
                break;

            case KeyPress:
                printf ("Got key!\n");
                len = XLookupString(&ev.xkey, buf, 16, &ks, &comp);
                if (len > 0 && isprint(buf[0]))
                {
                    buf[len]=0;
                    printf("String is: %s\n", buf);
                }
                else
                {
                    printf ("Key is: %d\n", (int)ks);
                }
        }

    }
}

这不可靠，但大多数时候它工作。 （这是显示键我现在输入到这个框）。你可以调查为什么它有时失败;）它也不能原则上显示热键。热键是抓取的键，只有一个客户端可以获取抓取的键。绝对没有什么可以在这里做，没有加载为此目的设计的特殊X11扩展（例如XEvIE）。

It's not reliable but most of the time it works. (It is showing keys I'm typing into this box right now). You may investigate why it does fail sometimes ;) Also it cannot show hotkeys in principle. Hotkeys are grabbed keys, and only one client can get a grabbed key. Absolutely nothing can be done here, short of loading a special X11 extension designed for this purpose (e.g. XEvIE).

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