我编写了一个简单的程序，它从串行端口（/dev/ttyS1）读取外部设备（条形码扫描仪）的字符并将其提供给当前活动的窗口（使用 XSendEvent）。
程序在速度较快的计算机上运行良好，但在速度较慢的计算机上，情况会发生（经常），字符的接收顺序与发送的顺序不同。例如，scanner 发送 1234567 到串口，我的程序发送 char 事件 1234567，但是活动程序（例如 xterm）收到 3127456。我尝试在各个地方调用 XSync 并添加usleep调用，但没有帮助。
有谁知道如何强制角色的“顺序”？
还是有其他方法可以将字符串发送到活动窗口（如果需要，我什至不介意使用外部程序）？
这是代码，也许我只是做错了什么：
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h> // serial port stuff
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <X11/Xlib.h>
/*
BarCode KeyboardFeeder: BCKF
Copyright (c) Milan Babuskov
Licence: GNU General Public Licence
Compile with: g++ bckf.cpp -lX11 -L /usr/X11R6/lib/ -o bckf
Keycodes: /usr/X11R6/include/X11/keysymdef.h
*/
//-----------------------------------------------------------------------------
void SendEvent(XKeyEvent *event, bool press)
{
if (press)
XSendEvent(event->display, event->window, True, KeyPressMask, (XEvent *)event);
else
XSendEvent(event->display, event->window, True, KeyReleaseMask, (XEvent *)event);
XSync(event->display, False);
}
//-----------------------------------------------------------------------------
bool sendChar(int c)
{
if (c >= 0x08 && c <= 0x1b) // send CR twice
{
sendChar(0xff0d);
c = 0xff0d;
}
printf("Sending char : 0x%02x\n", c);
char disp[] = ":0";
char *dp = getenv("DISPLAY");
if (!dp)
dp = disp;
else
printf("Using env.variable $DISPLAY = %s.\n", dp);
Display *dpy = XOpenDisplay(dp);
if (dpy == NULL)
{
printf("ERROR! Couldn't connect to display %s.\n", dp);
return false;
}
else
{
Window cur_focus; // focused window
int revert_to; // focus state
XGetInputFocus(dpy, &cur_focus, &revert_to); // get window with focus
if (cur_focus == None)
{
printf("WARNING! No window is focused\n");
return true;
}
else
{
XKeyEvent event;
event.display = dpy;
event.window = cur_focus;
event.root = RootWindow(event.display, DefaultScreen(event.display));
event.subwindow = None;
event.time = CurrentTime;
event.x = 1;
event.y = 1;
event.x_root = 1;
event.y_root = 1;
event.same_screen = True;
event.type = KeyPress;
event.state = 0;
event.keycode = XKeysymToKeycode(dpy, c);
SendEvent(&event, true);
event.type = KeyRelease;
SendEvent(&event, false);
}
XCloseDisplay(dpy);
}
usleep(20);
return true;
}
//-----------------------------------------------------------------------------
// Forward declaration
int InitComPort(const char *port);
//-----------------------------------------------------------------------------
int main(int argc, char **argv)
{
if (argc != 2)
{
printf("Usage: bckf serial_port\n");
return 1;
}
int port = InitComPort(argv[1]);
if (port == -1)
return 1;
while (true)
{
char buf[30];
ssize_t res = read(port, buf, 30);
if (res > 0)
{
for (ssize_t i=0; i<res; ++i)
{
int c = buf[i];
printf("Received char: 0x%02x\n", c);
if (c >= '0' && c <= '9' || c >= 0x08 && c <= 0x1b)
if (!sendChar(c)) // called from console?
break;
}
}
}
return 0;
}
//-----------------------------------------------------------------------------
int InitComPort(const char *port)
{
int c, res;
struct termios newtio;
struct termios oldtio;
// Open modem device for reading and writing and not as controlling tty
// because we don't want to get killed if linenoise sends CTRL-C.
int fdSerial = open(port, O_RDWR | O_NOCTTY );
if (fdSerial < 0)
{
printf(0, "Error opening port: %s\n%s", port, strerror(errno));
return -1;
}
tcgetattr(fdSerial,&oldtio); // save current port settings
memset(&newtio, 0, sizeof(newtio));
newtio.c_cflag = B9600 | CS8 | CLOCAL | CREAD; // CREAD : enable receiving characters
// CS8 : character size 8
// CLOCAL : Ignore modem control lines
newtio.c_iflag = IGNPAR; // IGNPAR : ignore bytes with parity errors
newtio.c_oflag = 0; // 0 : raw output (no echo, non-canonical)
//newtio.c_cc[VTIME] = timeout; // 10=1sec : inter-character timer (deciseconds)
newtio.c_cc[VMIN] = 1; // 50 : blocking read until 50 chars received
tcflush(fdSerial, TCIOFLUSH); // clear the line and...
tcsetattr(fdSerial,TCSANOW,&newtio); // ...activate new settings for the port
return fdSerial;
}
//-----------------------------------------------------------------------------