在X11-键盘挂钩中不消耗键盘事件即可收听键盘事件

fnx2tebb 于 2022-09-19 发布在 Linux

关注(0)|答案(4)|浏览(212)

我试着编写了一个程序，每当在Ubuntu(KDE)中按下每个键时，它都会挂钩键盘消息来发音每个键的名称；而不会干扰程序中键盘的正常操作(只需宣布键名称)。

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);
}

本程序只针对密钥a，可以扩展到其他密钥。

但当这个程序运行时，一些程序(如Chromium)在它们的编辑框中不会显示闪烁(光标)。此外，所有KDE热键都被禁用。

如何才能解决这个问题？

linux

来源：https://stackoverflow.com/questions/22749444/listening-to-keyboard-events-without-consuming-them-in-x11-keyboard-hooking

4条答案

按热度按时间

omjgkv6w1#

这是我的快速和肮脏的例子


# 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 %dn", (int)curFocus);
                if (curFocus != root)
                    XSelectInput(d, curFocus, 0);
                XGetInputFocus (d, &curFocus, &revert);
                printf ("New focus is %dn", (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: %sn", buf);
                }
                else
                {
                    printf ("Key is: %dn", (int)ks);
                }
        }

    }
}

这并不可靠，但大多数情况下它是有效的。(它显示的是我现在在这个框中输入的密钥)。你可能会调查为什么它有时会失败；)而且它原则上不能显示热键。热键是被抢占的密钥，只有一个客户端可以获得被抢占的密钥。这里除了加载专门为此目的而设计的X11扩展(例如XEvIE)外，什么都做不了。

赞(0）回复(0）举报 2022-09-19

zbwhf8kr2#

感谢n.m.的answer和parsa的评论，这是我的最终代码：


# include <X11/Xlib.h>

# include <stdlib.h>

# include <iostream>

using namespace std;

void* TaskCode(void* parg)
{
    int keycode = *((int*)parg);
    cout<< "nn" << keycode << "nn";
    if(keycode == XKeysymToKeycode(XOpenDisplay(0),'a'))
        system("espeak -v en " ""a"");
    delete (int*)parg;
    return 0;
}

void Action(int keycode)
{
    pthread_t thread;
    pthread_attr_t  attrs;
    pthread_attr_init(&attrs);
    pthread_attr_setdetachstate(&attrs,PTHREAD_CREATE_DETACHED);
    pthread_attr_setstacksize(&attrs, 1000);
    int* pthread_arg = new int;
    *pthread_arg = keycode;
    pthread_create(&thread,&attrs, TaskCode, (void*) pthread_arg);
}

int MyX11ErrorHandler(Display *, XErrorEvent *error_event)
{
   cout << "nn" "An X11-Functions error occured. Probably the focused window was closed.""n"
           "This error will be ignored." "n";
   cout<< "error_code: " << (unsigned)error_event -> error_code << "n";
   cout<< "minor_code: " << (unsigned)error_event -> minor_code << "n";
   cout<< "request_code: " << (unsigned)error_event -> request_code << "n";
   cout<< "resourceid: " << error_event -> resourceid << "n";
   cout<< "serial; " << error_event -> serial << "n";
   cout<< "type: " << error_event -> type << "nn";
   return 0;
}

int main()
{
    Display* display = XOpenDisplay(0);
    Window root = DefaultRootWindow(display);
    Window current_focus_window;
    int revert;

    XSetErrorHandler(MyX11ErrorHandler);

    XGetInputFocus(display, &current_focus_window, &revert);
    XSelectInput(display,current_focus_window,KeyPressMask | KeyReleaseMask | FocusChangeMask);

    while(true)
    {
        XEvent event;
        XNextEvent(display, &event);
        switch (event.type)
        {
            case FocusOut:
                if(current_focus_window != root)
                    XSelectInput(display, current_focus_window, 0);
                XGetInputFocus(display, &current_focus_window, &revert);
                if(current_focus_window == PointerRoot)
                    current_focus_window = root;
                XSelectInput(display, current_focus_window, KeyPressMask|KeyReleaseMask|FocusChangeMask);
                break;

            case KeyPress:
                Action(event.xkey.keycode);
                break;
        }
    }
}

将这些内容添加到Qt Creator的项目.pro文件中：

LIBS += -lX11
LIBS += -lpthread
LIBS += -lXtst

如有任何改进建议，我们将不胜感激。

为了存档，我还使用Grabing添加了我的最终代码：


# include <X11/Xlib.h>

# include <X11/Xutil.h>

# include <stdio.h>

# include <stdlib.h>

# include <string.h>

# include <iostream>

using namespace std;

void* TaskCode(void* parg)
{
    int keycode = *((int*)parg);
    cout<< "nn" << keycode << "nn";
    system("espeak -v en " ""a"");
    delete (int*)parg;
    return 0;
}

void SendKeyEvent(Display *display, XEvent event)
{
    Window current_focus_window;
    XKeyEvent& xkey = event.xkey;

    int current_focus_revert;
    XGetInputFocus(display, &current_focus_window, &current_focus_revert);       
    xkey.state = Mod2Mask;

    XSendEvent(display, InputFocus,  True, xkey.type, (XEvent *)(&event));
}

int GrabKey(Display* display, Window grab_window, int keycode)
{
    unsigned int    modifiers       = Mod2Mask; // numlock on
    //Window          grab_window     = DefaultRootWindow(display);
    Bool            owner_events    = True;
    int             pointer_mode    = GrabModeAsync;
    int             keyboard_mode   = GrabModeAsync;

    XGrabKey(display, keycode, modifiers, grab_window, owner_events, pointer_mode, keyboard_mode);
    return keycode;
}

void UngrabKey(Display* display, Window grab_window, int keycode)
{
    unsigned int    modifiers       = Mod2Mask; // numlock on

   // Window grab_window = DefaultRootWindow(display);
    XUngrabKey(display,keycode,modifiers,grab_window);
}

void Action(int keycode)
{
    pthread_t thread;
    int* pthread_arg = new int;

    *pthread_arg = keycode;
    pthread_create(&thread,0, TaskCode, (void*) pthread_arg);
}

int main()
{
    Display*    display = XOpenDisplay(0);
    Window      root    = DefaultRootWindow(display);
    XEvent      event;

    int keycode = XKeysymToKeycode(display,'a');
    GrabKey(display,root,keycode);

    XSelectInput(display, root, KeyPressMask | KeyReleaseMask);
    while(true)
    {
        XNextEvent(display, &event);
        switch(event.type)
        {
            case KeyPress:
                Action(event.xkey.keycode);
            case KeyRelease:
                SendKeyEvent(display,event);
            default:
                break;
        }
    }

    XCloseDisplay(display);
}

一切都很好，除了与所讨论的代码不同，它忽略了语言布局。按下任何类型的a，无论语言布局如何！

赞(0）回复(0）举报 2022-09-19

7qhs6swi3#

作为监听X事件的替代方案，还可以直接监听Linux输入事件：https://stackoverflow.com/a/27693340/21501

这样做的好处是可以修改正在运行的事件流，并阻止、编辑或生成输入事件。

赞(0）回复(0）举报 2022-09-19

iyr7buue4#

收听所有事件的正确方法是使用X记录扩展库，它是libXtst的一部分，显然安装在几乎每个X系统上。它是here文档，但由于文档不完整，您需要浏览以前的实现。Here是一个很好的工作演示，而here是一个更有能力和更完整的实现。

下面包括第一个示例的简化版本。


# include <stdio.h>

# include <X11/XKBlib.h>

# include <X11/extensions/record.h>

void key_pressed_cb(XPointer arg, XRecordInterceptData *d);

int scan(int verbose) {
    XRecordRange* rr;
    XRecordClientSpec rcs;
    XRecordContext rc;
    Display *dpy = XOpenDisplay(NULL);
    rr = XRecordAllocRange();
    rr->device_events.first = KeyPress;
    rr->device_events.last = ButtonReleaseMask;
    rcs = XRecordAllClients;
    rc = XRecordCreateContext (dpy, 0, &rcs, 1, &rr, 1);
    XFree (rr);
    XRecordEnableContext(dpy, rc, key_pressed_cb, NULL);
}

void key_pressed_cb(XPointer arg, XRecordInterceptData *d) {
    if (d->category != XRecordFromServer)
        return;

    int key = ((unsigned char*) d->data)[1];
    int type = ((unsigned char*) d->data)[0] & 0x7F;
    int repeat = d->data[2] & 1;

    if(!repeat) {
        switch (type) {
            case KeyPress:
                printf("key press %dn", key);
                break;
            case KeyRelease:
                printf("key release %dn", key);
                break;
            case ButtonPress:
                printf("button press %dn", key);
                break;
            case ButtonRelease:
                printf("button release %dn", key);
                break;
            default:
                break;
        }
    }
    XRecordFreeData (d);
}

int main() {
    scan(True);
    return 0;
}

gcc -o x1 x1.c -lX11 -lXtst

赞(0）回复(0）举报 2022-09-19

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在X11-键盘挂钩中不消耗键盘事件即可收听键盘事件

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