XCB + 记录 x11 扩展示例

Question

您能否提供通过 XCB 使用 record 扩展名的示例代码（任何语言）？有很多关于如何使用 Xlib (https://gist.github.com/whym/402801) 的示例，但我不明白如何将这部分 Xlib 代码转换为 XCB：

# Create a recording context; we only want key and mouse events
ctx = record_dpy.record_create_context(
    0,
    [record.AllClients],
    [{
        'core_requests': (0, 0),
        'core_replies': (0, 0),
        'ext_requests': (0, 0, 0, 0),
        'ext_replies': (0, 0, 0, 0),
        'delivered_events': (0, 0),
        'device_events': (X.KeyPress, X.KeyPress),
        'errors': (0, 0),
        'client_started': False,
        'client_died': False,
    }]
)

XCB docs for xcb_record_create_context(...) 完全是一团糟。任何工作代码都会有所帮助。

Answer 1

简短版本：您不想使用 RECORD 扩展。 Xlib 很乱，xcb 很丑。

无论如何，一些使用 Xlib 和 libXtst 的示例：https://github.com/nibrahim/showkeys/blob/master/tests/record-example.c

相同的代码（大致）转换为 xcb（请注意，这必须解析通常 libXtst 帮助的数据块本身，不知道这在实践中是否真的可能，但规范说这在理论上是可能的):

#include <stdio.h>
#include <stdlib.h>
#include <xcb/xcb.h>
#include <xcb/record.h>
#include <X11/Xlibint.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/cursorfont.h>
#include <X11/keysymdef.h>
#include <X11/keysym.h>
#include <X11/extensions/record.h>
#include <X11/extensions/XTest.h>

/* for this struct, refer to libxnee */
typedef union {
  unsigned char    type ;
  xEvent           event ;
  xResourceReq     req   ;
  xGenericReply    reply ;
  xError           error ;
  xConnSetupPrefix setup;
} XRecordDatum;

/*
 * FIXME: We need define a private struct for callback function,
 * to store cur_x, cur_y, data_disp, ctrl_disp etc.
 */
static xcb_connection_t *data_disp = NULL;
static xcb_connection_t *ctrl_disp = NULL;

/* stop flag */
int stop = 0;

size_t event_callback(xcb_record_enable_context_reply_t *reply, uint8_t *data_);

int main ()
{
  ctrl_disp = xcb_connect (NULL, NULL);
  data_disp = xcb_connect (NULL, NULL);

  if (xcb_connection_has_error(ctrl_disp) || xcb_connection_has_error(data_disp)) {
    fprintf (stderr, "Error to open local display!\n");
    exit (1);
  }

  const xcb_query_extension_reply_t *query_ext = xcb_get_extension_data(ctrl_disp, &xcb_record_id);
  if (!query_ext) {
    fprintf (stderr, "RECORD extension not supported on this X server!\n");
    exit (2);
  }

  xcb_record_query_version_reply_t *version_reply = xcb_record_query_version_reply(ctrl_disp,
      xcb_record_query_version(ctrl_disp, XCB_RECORD_MAJOR_VERSION, XCB_RECORD_MINOR_VERSION), NULL);
  if (!version_reply) {
    fprintf (stderr, "This should not happen: Can't get RECORD version\n");
    exit (2);
  }

  printf ("RECORD extension for local server is version is %d.%d\n", version_reply->major_version, version_reply->minor_version);
  free(version_reply);

  xcb_record_range_t rr;
  xcb_record_client_spec_t rcs;
  xcb_record_context_t rc = xcb_generate_id(ctrl_disp);

  memset(&rr, 0, sizeof(rr));
  rr.device_events.first = XCB_KEY_PRESS;
  rr.device_events.last = XCB_MOTION_NOTIFY;
  rcs = XCB_RECORD_CS_ALL_CLIENTS;

  xcb_void_cookie_t create_cookie = xcb_record_create_context_checked (ctrl_disp, rc, 0, 1, 1, &rcs, &rr);
  xcb_generic_error_t *error = xcb_request_check(ctrl_disp, create_cookie);
  if (error) {
    fprintf (stderr, "Could not create a record context!\n");
    free(error);
    exit (4);
  }

  /* The above xcb_request_check() makes sure the server already handled the
   * CreateContext request, thus this isn't needed anymore:
   * XSync(ctrl_disp, 0);
   */

  xcb_record_enable_context_cookie_t cookie = xcb_record_enable_context(data_disp, rc);

  while (!stop) {
    xcb_record_enable_context_reply_t *reply = xcb_record_enable_context_reply(data_disp, cookie, NULL);
    if (!reply)
      break;
    if (reply->client_swapped) {
      fprintf (stderr, "I am too lazy to implement byteswapping\n");
      exit(42);
    }

    if (reply->category == 0 /* XRecordFromServer */) {
      size_t offset = 0;
      uint8_t *data = xcb_record_enable_context_data(reply);
      while (offset < reply->length<<2) {
        offset += event_callback(reply, &data[offset]);
      }
    }
    free(reply);
  }

  xcb_record_disable_context (ctrl_disp, rc);
  xcb_record_free_context (ctrl_disp, rc);
  xcb_flush (ctrl_disp);

  xcb_disconnect (data_disp);
  xcb_disconnect (ctrl_disp);
  return 0;
}

size_t event_callback(xcb_record_enable_context_reply_t *reply, uint8_t *data_)
{
  /* FIXME: we need use XQueryPointer to get the first location */
  static int cur_x = 0;
  static int cur_y = 0;

  XRecordDatum *data = (XRecordDatum*) data_;

  int event_type = data->type;

  BYTE btncode, keycode;
  btncode = keycode = data->event.u.u.detail;

  int rootx = data->event.u.keyButtonPointer.rootX;
  int rooty = data->event.u.keyButtonPointer.rootY;
  int time = reply->server_time;

  switch (event_type) {
  case KeyPress:
    /* if escape is pressed, stop the loop and clean up, then exit */
    if (keycode == 9) stop = 1;

    /* Note: you should not use data_disp to do normal X operations !!!*/
    /*printf ("KeyPress: \t%s\n", XKeysymToString(XKeycodeToKeysym(ctrl_disp, keycode, 0)));*/
    printf ("KeyPress: \t%d\n", keycode);
    break;
  case KeyRelease:
    /*printf ("KeyRelease: \t%s\n", XKeysymToString(XKeycodeToKeysym(ctrl_disp, keycode, 0)));*/
    printf ("KeyRelease: \t%d\n", keycode);
    break;
  case ButtonPress:
    /* printf ("ButtonPress: /t%d, rootX=%d, rootY=%d", btncode, cur_x, cur_y); */
    break;
  case ButtonRelease:
    /* printf ("ButtonRelease: /t%d, rootX=%d, rootY=%d", btncode, cur_x, cur_y); */
    break;
  case MotionNotify:
    /* printf ("MouseMove: /trootX=%d, rootY=%d",rootx, rooty); */
    cur_x = rootx;
    cur_y = rooty;
    break;
  case CreateNotify:
    break;
  case DestroyNotify:
    break;
  case NoExpose:
    break;
  case Expose:
    break;
  default:
    break;
  }

  printf (", time=%d\n", time);

  if (data_[0] == 0)
    /* reply */
    return ((*(uint32_t*) &data_[4]) + 8) << 2;
  /* Error or event TODO: What about XGE events? */
  return 32;
}