如何从C代码配置libinput设备？

Question

在wayland上没有libinput的配置文件。这通常不是一个问题，因为桌面环境(如Gnome)通常提供一种配置设备的方法。但是，没有办法为单击垫设备启用中间单击仿真。默认情况下(使用按钮区域，以便我可以用触摸屏的右下角右键单击)，也会创建一个中间按钮区域。这通常导致我点击中间按钮时，我试图左键和中点代替(导致某些东西被粘贴)。如果启用了中间仿真，则可以禁用这个中间单击区域，但是，由于Gnome没有提供配置该区域的方法，所以我决定尝试构建自己的程序。

我查看了libinput的API文档和示例(不幸的是，我似乎找不到设备配置的任何示例)。下面的代码是我放在一起的代码(用注释中的命令编译)。

/**
 * Simple program to setup libinput touchpad to use middle click emulation in wayland.
 *
 * To build install libinput-devel and libudev-devel
 * gcc -o middleemulation main.c `pkg-config --cflags --libs libinput libudev`
 * 
 * Copyright 2019 Marcus Behel
 *
 *Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <libudev.h>
#include <libinput.h>

static int open_restricted(const char *path, int flags, void *user_data){
  int fd = open(path, flags);
  return fd < 0 ? -errno : fd;
}

static void close_restricted(int fd, void *user_data){
  close(fd);
}

const static struct libinput_interface interface = {
        .open_restricted = open_restricted,
        .close_restricted = close_restricted,
};

int main(void){

  struct libinput *li;
  struct libinput_event *ev;
  struct udev *udev = udev_new();
  int dev_count = 0, tp_count = 0;

  li = libinput_udev_create_context(&interface, NULL, udev);
  libinput_udev_assign_seat(li, "seat0");
  libinput_dispatch(li);

  while ((ev = libinput_get_event(li))) {
    if (libinput_event_get_type(ev) == LIBINPUT_EVENT_DEVICE_ADDED){
      dev_count++;

      double w = 0, h = 0;
      struct libinput_device *dev = libinput_event_get_device(ev);
      const char *name = libinput_device_get_name(dev);
      if(libinput_device_has_capability(dev, LIBINPUT_DEVICE_CAP_POINTER) &&
     libinput_device_get_size(dev, &w, &h) == 0){
    // Pointer with a size is a touchpad
    tp_count++;

    // This is a touchpad. Enable middle click emulation
    printf("Found touchpad: '%s'.\n", name);

    printf("Is middle click enabled: %s.\n", libinput_device_config_middle_emulation_get_enabled(dev) ? "true" : "false");

    if(libinput_device_config_middle_emulation_is_available(dev)){
      printf("Enabling middle emulation for device...");
      enum libinput_config_status err = libinput_device_config_middle_emulation_set_enabled(dev, LIBINPUT_CONFIG_MIDDLE_EMULATION_ENABLED);

      if(err == LIBINPUT_CONFIG_STATUS_SUCCESS){
        printf("Succeeded.\n");
      }else{
        printf("Failed.\n");
      }

      printf("Is middle click enabled: %s.\n\n", libinput_device_config_middle_emulation_get_enabled(dev) ? "true" : "false");

    }else{
      printf("Device does not support middle emulation.\n\n");
    }
      }
    }

    libinput_event_destroy(ev);
    libinput_dispatch(li);
  }

  libinput_unref(li);

  if(dev_count == 0){
    fprintf(stderr, "No libinput devices were found. Run this as root and make sure libinput driver is enabled.\n");
    return 1;
  }

  if(tp_count == 0){
    printf("No touchpads found on this system.");
  }

  return 0;
}

我已经测试了Ubuntu18.04(戴尔Inspiron 5000)和Fedora 30 (惠普展馆15)。在这两种情况下，程序都表示成功，但是当运行libinput列表设备时，它仍然显示中间模拟是禁用的，并且行为没有改变。

节目输出(惠普馆)

Found touchpad: 'SynPS/2 Synaptics TouchPad'.
Is middle click enabled: false.
Enabling middle emulation for device...Succeeded.
Is middle click enabled: true.

程序运行后来自libinput列表设备的输出

Device:           SynPS/2 Synaptics TouchPad
Kernel:           /dev/input/event4
Group:            9
Seat:             seat0, default
Size:             106x61mm
Capabilities:     pointer gesture
Tap-to-click:     disabled
Tap-and-drag:     enabled
Tap drag lock:    disabled
Left-handed:      disabled
Nat.scrolling:    disabled
Middle emulation: disabled
Calibration:      n/a
Scroll methods:   *two-finger edge 
Click methods:    *button-areas clickfinger 
Disable-w-typing: enabled
Accel profiles:   none
Rotation:         n/a

Answer 1

看起来，这需要一个预加载库才能按预期工作。这里的解决方案是：https://github.com/gaul/libinput-force-middle-click-emulation为我工作。