Question

我一直在研究XCB教程，但我坚持这个。在此示例中，当您按下ESC键时程序退出。但是在示例代码中，我无法弄清楚“case 9”如何捕获ESC密钥。我搜索并查看了整个xcb.h和xproto.h以及ASCII表。

我以为我明白了，直到我得到“案例9”。这是我完全迷失的地方。所以基本上，他们从哪里获得9？这与ESC？

的对应关系如何？

这是我正在研究的示例代码：

#include <stdlib.h>
#include <stdio.h>
#include <string.h> 
#include <xcb/xcb.h>

#define WIDTH 300
#define HEIGHT 100 

static xcb_gc_t gc_font_get (xcb_connection_t *c,
                             xcb_screen_t     *screen,
                             xcb_window_t      window,
                             const char       *font_name);

static void text_draw (xcb_connection_t *c,
                       xcb_screen_t     *screen,
                       xcb_window_t      window,
                       int16_t           x1,
                       int16_t           y1,
                       const char       *label)
{
  xcb_void_cookie_t    cookie_gc;
  xcb_void_cookie_t    cookie_text;
  xcb_generic_error_t *error;
  xcb_gcontext_t       gc;
  uint8_t              length;

  length = strlen (label);

  gc = gc_font_get(c, screen, window, "7x13");

  cookie_text = xcb_image_text_8_checked (c, length, window, gc,
                                          x1,
                                          y1, label);
  error = xcb_request_check (c, cookie_text);
  if (error) {
    fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code);
    xcb_disconnect (c);
    exit (-1);
  }

  cookie_gc = xcb_free_gc (c, gc);
  error = xcb_request_check (c, cookie_gc);
  if (error) {
    fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code);
    xcb_disconnect (c);
    exit (-1);
  }
}

static xcb_gc_t gc_font_get (xcb_connection_t *c,
                             xcb_screen_t     *screen,
                             xcb_window_t      window,
                             const char       *font_name)
{
  uint32_t             value_list[3];
  xcb_void_cookie_t    cookie_font;
  xcb_void_cookie_t    cookie_gc;
  xcb_generic_error_t *error;
  xcb_font_t           font;
  xcb_gcontext_t       gc;
  uint32_t             mask;

  font = xcb_generate_id (c);
  cookie_font = xcb_open_font_checked (c, font,
                                       strlen (font_name),
                                       font_name);

  error = xcb_request_check (c, cookie_font);
  if (error) {
    fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code);
    xcb_disconnect (c);
    return -1;
  }

  gc = xcb_generate_id (c);
  mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
  value_list[0] = screen->black_pixel;
  value_list[1] = screen->white_pixel;
  value_list[2] = font;
  cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list);
  error = xcb_request_check (c, cookie_gc);
  if (error) {
    fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code);
    xcb_disconnect (c);
    exit (-1);
  }

  cookie_font = xcb_close_font_checked (c, font);
  error = xcb_request_check (c, cookie_font);
  if (error) {
    fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code);
    xcb_disconnect (c);
    exit (-1);
  }

  return gc;
}

int main ()
{
  xcb_screen_iterator_t screen_iter;
  xcb_connection_t     *c;
  const xcb_setup_t    *setup;
  xcb_screen_t         *screen;
  xcb_generic_event_t  *e;
  xcb_generic_error_t  *error;
  xcb_void_cookie_t     cookie_window;
  xcb_void_cookie_t     cookie_map;
  xcb_window_t          window;
  uint32_t              mask;
  uint32_t              values[2];
  int                   screen_number;

  /* getting the connection */
  c = xcb_connect (NULL, &screen_number);
  if (!c) {
    fprintf (stderr, "ERROR: can't connect to an X server\n");
    return -1;
  }

  /* getting the current screen */
  setup = xcb_get_setup (c);

  screen = NULL;
  screen_iter = xcb_setup_roots_iterator (setup);
  for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter))
    if (screen_number == 0)
      {
        screen = screen_iter.data;
        break;
      }
  if (!screen) {
    fprintf (stderr, "ERROR: can't get the current screen\n");
    xcb_disconnect (c);
    return -1;
  }

  /* creating the window */
  window = xcb_generate_id (c);
  mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
  values[0] = screen->white_pixel;
  values[1] =
    XCB_EVENT_MASK_KEY_RELEASE |
    XCB_EVENT_MASK_BUTTON_PRESS |
    XCB_EVENT_MASK_EXPOSURE |
    XCB_EVENT_MASK_POINTER_MOTION;
  cookie_window = xcb_create_window_checked (c,
                                             screen->root_depth,
                                             window, screen->root,
                                             20, 200, WIDTH, HEIGHT,
                                             0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
                                             screen->root_visual,
                                             mask, values);
  cookie_map = xcb_map_window_checked (c, window);

  /* error managing */
  error = xcb_request_check (c, cookie_window);
  if (error) {
    fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code);
    xcb_disconnect (c);
    return -1;
  }
  error = xcb_request_check (c, cookie_map);
  if (error) {
    fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code);
    xcb_disconnect (c);
    return -1;
  }

  xcb_flush(c);

  while (1) {
    e = xcb_poll_for_event(c);
    if (e) {
      switch (e->response_type & ~0x80) {
      case XCB_EXPOSE: {
        char *text;

        text = "Press ESC key to exit...";
        text_draw (c, screen, window, 10, HEIGHT - 10, text);
        break;
      }
      case XCB_KEY_RELEASE: {
        xcb_key_release_event_t *ev;

        ev = (xcb_key_release_event_t *)e;

        switch (ev->detail) {
          /* ESC */
        case 9:
          free (e);
          xcb_disconnect (c);
          return 0;
        }
      }
      }
      free (e);
    }
  }

  return 0;
}

由于

Answer 1

低级X KeyCode位于8..255范围内，代表键盘的物理布局。据推测，在实践中，值9（＆＃34; 1＆＃34;相对于范围的起点，即左上角）是 Esc 键。

话虽如此，硬编码特定于设备的知识似乎是一个非常糟糕的主意，而不是查找哪个密钥与Esc KeySym相关联。

此链接似乎提供了一些有用的信息：

https://tronche.com/gui/x/xlib/input/keyboard-encoding.html

XCB的事件处理如何检测C中的ESC键？

1 个答案: