TERMKEY_GETKEY(3)

NAME
termkey_getkey, termkey_getkey_force - retrieve the next key event

SYNOPSIS
#include <termkey.h>

TermKeyResult termkey_getkey(TermKey *tk, TermKeyKey *key);
TermKeyResult termkey_getkey_force(TermKey *tk, TermKeyKey *key);

Link with -ltermkey.

DESCRIPTION
termkey_getkey() attempts to retrieve a single keypress event from the termkey(7) instance buffer, and put it in the structure referred to by key. It returns one of the following values:

TERMKEY_RES_KEY
    a complete keypress was removed from the buffer, and has been placed in the key structure.

TERMKEY_RES_AGAIN
    a partial keypress event was found in the buffer, but it does not yet contain all the bytes required. An indication of what termkey_getkey_force() would return has been placed in the key structure.

TERMKEY_RES_NONE
    no bytes are waiting in the buffer.

TERMKEY_RES_EOF
     no bytes are ready and the input stream is now closed.

TERMKEY_RES_ERROR
    called with terminal IO stopped, due to termkey_stop(3). In this case errno will be set to EINVAL.

termkey_getkey_force() is similar to termkey_getkey() but will not return TERMKEY_RES_AGAIN if a partial match is found. Instead, it will force an interpretation of the bytes, even if this means interpreting the start of an Escape-prefixed multi-byte sequence as a literal Escape key followed by normal letters.

Neither of these functions will block or perform any IO operations on the underlying filehandle. To use the instance in an asynchronous program, see termkey_advisereadable(3). For a blocking call suitable for use in a synchronous program, use termkey_waitkey(3) instead of termkey_getkey(). For providing input without a readable filehandle, use termkey_push_bytes(3).

Before returning, this function canonicalises the key structure according to the rules given for termkey_canonicalise(3).

RETURN VALUE
termkey_getkey() returns an enumeration of one of TERMKEY_RES_KEY, TEMRKEY_RES_AGAIN, TERMKEY_RES_NONE, TERMKEY_RES_EOF or TERMKEY_RES_ERROR. termkey_getkey_force() returns one of the above, except for TERMKEY_RES_AGAIN.

EXAMPLE
The following example program prints details of every keypress until the user presses Ctrl-C. It demonstrates how to use the termkey instance in a typical poll(2)-driven asynchronous program, which may include mixed IO with other file handles.

// <poll.h> might need this for sigset_t
#define _XOPEN_SOURCE 600

#include <poll.h>
#include <stdio.h>

#include "termkey.h"

static void on_key(TermKey *tk, TermKeyKey *key)
{
  char buffer[50];
  termkey_strfkey(tk, buffer, sizeof buffer, key, TERMKEY_FORMAT_VIM);
  printf("%s\n", buffer);
}

int main(int argc, char *argv[])
{
  TERMKEY_CHECK_VERSION;

  TermKey *tk = termkey_new(0, 0);

  if(!tk) {
    fprintf(stderr, "Cannot allocate termkey instance\n");
    exit(1);
  }

  struct pollfd fd;

  fd.fd = 0; /* the file descriptor we passed to termkey_new() */
  fd.events = POLLIN;

  TermKeyResult ret;
  TermKeyKey key;

  int running = 1;
  int nextwait = -1;

  while(running) {
    if(poll(&fd, 1, nextwait) == 0) {
      // Timed out
      if(termkey_getkey_force(tk, &key) == TERMKEY_RES_KEY)
        on_key(tk, &key);
    }

    if(fd.revents & (POLLIN|POLLHUP|POLLERR))
      termkey_advisereadable(tk);

    while((ret = termkey_getkey(tk, &key)) == TERMKEY_RES_KEY) {
      on_key(tk, &key);

      if(key.type == TERMKEY_TYPE_UNICODE &&
         key.modifiers & TERMKEY_KEYMOD_CTRL &&
         (key.code.codepoint == 'C' || key.code.codepoint == 'c'))
        running = 0;
    }

    if(ret == TERMKEY_RES_AGAIN)
      nextwait = termkey_get_waittime(tk);
    else
      nextwait = -1;
  }

  termkey_destroy(tk);
}

SEE ALSO
termkey_advisereadable(3), termkey_waitkey(3), termkey_get_waittime(3), termkey(7)