Linux中的鼠标事件处理? [英] Mouse event handling in Linux?

问题描述

我有一个事件处理代码，该代码可以为触摸板读取Linux的/dev/input/并根据按下/释放的按钮来打印结果.

I have an event handling code that reads Linux's /dev/input/ for my touchpad and prints result on the basis of which button is pressed/released.

尽管.截至目前，我的代码在终端上运行时正在等待按钮按下.我的下一步是将这个事件处理线程与另一个线程(不是基于事件的线程)一起运行.如果我继续通过读取终端上的输入来处理事件，则由于main()一直在等待按钮按下，因此我将无法执行其他线程作为main()的一部分.

Although. as of now my code is waiting on a button press while running on terminal. My next step is to run this event handling thread along with another thread (not event based). If I continue handling event by reading input at terminal, I will not be able to execute other threads as a part of my main() as main() keeps on waiting for the button press:

int main(int argc, char** argv)
{
    *Mouse event handling code here*
    return 0; 
}

是否有其他方法，例如读取中断?还是我仍然可以采用这种方法并在代码中进行修改，以使其成为线程的一部分(例如，可以让我的线程将这些输入作为参数来等待)吗?

Is there a different approach like reading interrupts instead? Or can I still take this approach and make amends in my code to make this work as a part of a thread (like can I make my thread to wait on these inputs as arguments)?

推荐答案

如果将事件设备描述符设为非阻塞(通过使用O_NONBLOCK标志打开它们)，则可以非常轻松地使用

If you make the event device descriptors nonblocking (by opening them with the O_NONBLOCK flag), you can very easily use `poll() to wait until one of them has events you can read.

请考虑以下示例程序 example.c :

#define  _POSIX_C_SOURCE  200809L
#define  _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/input.h>
#include <termios.h>
#include <poll.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>

/* Maximum number of input sources, including the terminal. */
#ifndef   MAX_INPUTS
#define   MAX_INPUTS  32
#endif

/* Maximum wait for events, in milliseconds (1000 ms = 1 second). */
#ifndef   INTERVAL_MS
#define   INTERVAL_MS  100
#endif

int main(int argc, char *argv[])
{
    unsigned char       keys[16];
    struct input_event  event;
    struct termios      config, oldconfig;
    struct pollfd       src[MAX_INPUTS];
    size_t              srcs, i, done;
    ssize_t             n;
    int                 arg, nsrcs;

    if (!isatty(STDIN_FILENO)) {
        fprintf(stderr, "Standard input is not a terminal.\n");
        return EXIT_FAILURE;
    }

    /* Save old terminal configuration. */
    if (tcgetattr(STDIN_FILENO, &oldconfig) == -1 ||
        tcgetattr(STDIN_FILENO, &config) == -1) {
        fprintf(stderr, "Cannot get terminal settings: %s.\n", strerror(errno));
        return EXIT_FAILURE;
    }

    /* Set new terminal configuration. */
    config.c_iflag &= ~(IGNBRK | BRKINT | PARMRK);
    config.c_lflag &= ~(ICANON | ISIG | ECHO | IEXTEN | TOSTOP);
    config.c_cc[VMIN] = 0;
    config.c_cc[VTIME] = 0;
    config.c_cc[VSTART] = 0;
    config.c_cc[VSTOP] = 0;
    if (tcsetattr(STDIN_FILENO, TCSANOW, &config) == -1) {
        const int  saved_errno = errno;
        tcsetattr(STDIN_FILENO, TCSANOW, &oldconfig);
        fprintf(stderr, "Cannot set terminal settings: %s.\n", strerror(saved_errno));
        return EXIT_FAILURE;
    }

    /* The very first input source is the terminal. */
    src[0].fd = STDIN_FILENO;
    src[0].events = POLLIN;
    src[0].revents = 0;
    srcs = 1;

    /* Add input devices from command line. */
    for (arg = 1; arg < argc; arg++) {
        int  fd;

        fd = open(argv[arg], O_RDONLY | O_NOCTTY | O_NONBLOCK);
        if (fd == -1) {
            fprintf(stderr, "Skipping input device %s: %s.\n", argv[arg], strerror(errno));
            continue;
        }

        if (srcs >= MAX_INPUTS) {
            fprintf(stderr, "Too many event sources.\n");
            return EXIT_FAILURE;
        }

        /* Optional: Grab input device, so only we receive its events. */
        ioctl(fd, EVIOCGRAB, 1);

        src[srcs].fd = fd;
        src[srcs].events = POLLIN;
        src[srcs].revents = 0;
        srcs++;
    }

    printf("Ready. Press Q to exit.\n");
    fflush(stdout);

    done = 0;
    while (!done) {

        nsrcs = poll(src, srcs, INTERVAL_MS);
        if (nsrcs == -1) {
            if (errno == EINTR)
                continue;
            fprintf(stderr, "poll(): %s.\n", strerror(errno));
            break;
        }

        /* Terminal is not an input source. */
        if (src[0].revents & POLLIN) {
            n = read(src[0].fd, keys, sizeof keys);
            if (n > 0) {
                for (i = 0; i < n; i++) {
                    if (keys[i] == 'q' || keys[i] == 'Q')
                        done = 1;
                    if (keys[i] >= 32 && keys[i] <= 126)
                        printf("Key '%c' = 0x%02x = %u pressed\n", keys[i], keys[i], keys[i]);
                    else
                    if (keys[i])
                        printf("Key '\\%03o' = 0x%02x = %u pressed\n", keys[i], keys[i], keys[i]);
                    else
                        printf("NUL key (0) pressed\n");
                }
                fflush(stdout);
            }
            src[0].revents = 0;
        }

        /* Check the other input sources. */
        for (i = 1; i < srcs; i++) {
            if (src[i].revents & POLLIN) {
                while (1) {
                    n = read(src[i].fd, &event, sizeof event);
                    if (n != sizeof event)
                        break;

                    if (event.type == EV_KEY && event.code == BTN_LEFT) {
                        if (event.value > 0)
                            printf("Left mouse button pressed\n");
                        else
                            printf("Left mouse button released\n");
                    }

                    if (event.type == EV_KEY && event.code == BTN_RIGHT) {
                        if (event.value > 0)
                            printf("Right mouse button pressed\n");
                        else
                            printf("Right mouse button released\n");
                    }
                }
                fflush(stdout);
            }
            src[i].revents = 0;             
        }
    }

    /* Close input devices. */
    for (i = 1; i < srcs; i++)
        close(src[i].fd);

    /* Restore terminal settings. */
    tcsetattr(src[0].fd, TCSAFLUSH, &oldconfig);

    printf("All done.\n");
    return EXIT_SUCCESS;
}

使用例如

gcc -Wall -O2 example.c -o example

并使用例如

sudo ./example /dev/input/event5

其中，/dev/input/event5是鼠标事件设备.请注意，您可以阅读/sys/class/input/event5/device/name来找出设备的名称(据内核所知；这些名称与evtest在以root用户身份运行时显示的名称相同).

where /dev/input/event5 is a mouse event device. Note that you can read /sys/class/input/event5/device/name to find out the name of the device (as far as the kernel knows it; these are the same names evtest shows when run as root).

如果不确定，您可以随时运行

If you are not sure, you can always run

for N in /sys/class/input/event*/device/name ; do 
    DEV="${N%%/device/name}" ; DEV="/dev/${DEV##/sys/class/}" ;
    NAME="$(cat "$N" 2>/dev/null)" ;
    printf "%s: %s\n" "$DEV" "$NAME" ;
done

在Bash或Dash或POSIX Shell中，以查看可以尝试使用的事件设备.

in a Bash or Dash or a POSIX shell, to see what event devices you can try.

上面的示例程序必须从终端或控制台运行，因为它也从终端获取输入.它将终端设置为非阻塞非规范模式，在该模式下它可以接收单独的按键.请注意，某些按键(例如光标和功能键)实际上长几个字符，以ESC(\033)开头.

The example program above must be run from a terminal or console, because it also takes input from the terminal. It sets the terminal into nonblocking non-canonical mode, where it can receive individual keypresses. Do note that some keypresses, like cursor and function keys, are actually several characters long, beginning with an ESC (\033).

将输入事件循环拆分为单独的线程也很常见.仅仅多了十几行，但是问题"变成了独立线程如何通知主(或其他)线程新的输入事件/命令已经到达.上面的非阻塞poll()方法通常更容易以非常健壮，直接的方式实现.

It is also common to split that input event loop into a separate thread. It is just a dozen or so lines more, but the "problem" then becomes how the separate thread informs the main (or other) threads that new input events/commands have arrived. The non-blocking poll() approach above is usually easier to implement in a very robust, straightforward manner.

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