在 X11 中侦听键盘事件而不使用它们 - 键盘挂钩

快速而肮脏的例子

#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);
                }
        }
    }
}

不可靠，但大多数时候它都有效。（它显示我现在正在此框中键入的键）。您可以调查为什么它有时会失败;)它原则上也不能显示热键。热键是抓取的密钥，只有一个客户端可以获取抓取的密钥。除了加载为此目的设计的特殊 X11 扩展（例如 XEvIE）之外，这里绝对无能为力。

感谢 n.m. 的回答和 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;
        }
    }
}

将这些添加到Qt Creator的项目.pro文件中：

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

任何改进建议将不胜感激。

为了存档，我还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。按一个类型a任何语言布局的无级

作为侦听 X 事件的替代方法，也可以直接侦听 Linux 输入事件： https://stackoverflow.com/a/27693340/21501

这样做的好处是可以修改正在进行的事件流，并阻止、编辑或生成输入事件。

收听所有事件的正确方法是使用 X 记录扩展库，这是 libXtst 的一部分，显然几乎安装在每个 X 系统上。此处记录了它，但由于文档不完整，因此您需要浏览以前的实现。这是一个不错的工作演示，这是一个更强大和完整的实现。

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