screenhack/textclient.c

/* xscreensaver, Copyright (c) 2012-2020 Jamie Zawinski <jwz@jwz.org>
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation.  No representations are made about the suitability of this
 * software for any purpose.  It is provided "as is" without express or
 * implied warranty.
 *
 * Running programs under a pipe or pty and returning bytes from them.
 * Uses these X resources:
 *
 * program:             What to run.  Usually "xscreensaver-text".
 * relaunchDelay: secs  How long after the command dies before restarting.
 * usePty: bool         Whether to run the command interactively.
 * metaSendsESC: bool   Whether to send Alt-x as ESC x in pty-mode.
 * swapBSDEL: bool      Swap Backspace and Delete in pty-mode.
 *
 * On iOS and Android, textclient-mobile.c is used instead.
 */

#include "utils.h"

#if !defined(HAVE_IPHONE) && !defined(HAVE_ANDROID)  /* whole file */

#include "textclient.h"
#include "resources.h"

#ifndef HAVE_COCOA
# define XK_MISCELLANY
# include <X11/keysymdef.h>
# include <X11/Xatom.h>
# include <X11/Intrinsic.h>
#endif

#include <stdio.h>

#include <signal.h>
#include <sys/wait.h>

#ifdef HAVE_UNISTD_H
# include <unistd.h>
# include <fcntl.h>  /* for O_RDWR */
#endif

#ifdef HAVE_FORKPTY
# include <sys/ioctl.h>
# ifdef HAVE_PTY_H
#  include <pty.h>
# endif
# ifdef HAVE_UTIL_H
#  include <util.h>
# endif
# ifdef HAVE_SYS_TERMIOS_H
#  include <sys/termios.h>
# endif
#endif /* HAVE_FORKPTY */

#undef DEBUG

extern const char *progname;

struct text_data {
  Display *dpy;
  char *program;
  int pix_w, pix_h, char_w, char_h;
  int max_lines;

  Bool pty_p;
  XtIntervalId pipe_timer;
  FILE *pipe;
  pid_t pid;
  XtInputId pipe_id;
  Bool input_available_p;
  Time subproc_relaunch_delay;
  XComposeStatus compose;

  Bool meta_sends_esc_p;
  Bool swap_bs_del_p;
  Bool meta_done_once;
  unsigned int meta_mask;

  const char *out_buffer;
  int out_column;
};


static void
subproc_cb (XtPointer closure, int *source, XtInputId *id)
{
  text_data *d = (text_data *) closure;
# ifdef DEBUG
  if (! d->input_available_p)
    fprintf (stderr, "%s: textclient: input available\n", progname);
# endif
  d->input_available_p = True;
}


# define BACKSLASH(c) \
  (! ((c >= 'a' && c <= 'z') || \
      (c >= 'A' && c <= 'Z') || \
      (c >= '0' && c <= '9') || \
      c == '.' || c == '_' || c == '-' || c == '+' || c == '/'))

#ifdef HAVE_COCOA
static char *
escape_str (char *s, const char *src)
{
  while (*src) {
    char c = *src++;
    if (BACKSLASH(c)) *s++ = '\\';
    *s++ = c;
  }
  return s;
}
#endif


/* Let's see if we're able to fork and exec at all. Thanks, macOS.
 */
static Bool
selftest (void)
{
  static Bool done = False;
  pid_t pid;
  char buf [255];
  if (done) return True;

  pid = fork ();
  switch ((int) pid)
    {
    case -1:
      sprintf (buf, "%s: textclient: selftest: couldn't fork", progname);
      perror (buf);
      return False;

    case 0:                                     /* child */
      {
        char * const av[] = { "/bin/sh", "-c", "true", 0 };
        execvp (av[0], av);
        exit (1);  /* exits child fork */
        break;
      }

    default:                                    /* parent */
      {
        int status = -1;
        int i;
        /* Busy-loops are bad mmmmkayyyy */
        struct timeval tv;
        tv.tv_sec  = 0;
        tv.tv_usec = 100000L;           /* 0.1 sec */
        for (i = 0; i < 50; i++) {      /* 5 sec max */
          pid_t pid2 = waitpid (pid, &status, 0);
          if (pid == pid2) break;
          (void) select (0, 0, 0, 0, &tv);
        }

        if (status != 0)
          {
# ifdef DEBUG
            fprintf (stderr, "%s: selftest: textclient: status %d\n",
                     progname, status);
# endif
            return False;
          }
        else
          {
# ifdef DEBUG
            fprintf (stderr, "%s: textclient: selftest ok\n", progname);
# endif
            done = True;
          }
        break;
      }
    }

  return True;
}


static void start_timer (text_data *d);

static void
launch_text_generator (text_data *d)
{
  XtAppContext app = XtDisplayToApplicationContext (d->dpy);
  char buf[255];
  const char *oprogram = d->program;
  char *s;

  size_t oprogram_size = strlen(oprogram);
  size_t len;

# ifdef HAVE_COCOA
  /* /bin/sh on OS X 10.10 wipes out the PATH. */
  const char *path = getenv("PATH");
  size_t cmd_capacity = (oprogram_size + strlen(path)) * 2 + 100;
  char *cmd = s = malloc (cmd_capacity);
  strcpy (s, "export PATH=");
  s += strlen (s);
  s = escape_str (s, path);
  strcpy (s, "; ");
  s += strlen (s);
# else
  char *cmd = s = malloc ((strlen(oprogram)) * 2 + 100);
# endif

  if (!selftest())
    {
      if (!d->out_buffer || !*d->out_buffer)
        d->out_buffer = "Can't exec; Gatekeeper problem?\r\n\r\n";
      start_timer (d);
      return;
    }

  strcpy (s, "( ");
  strcat (s, oprogram);
  s += strlen (s);

  /* Kludge!  Special-case "xscreensaver-text" to tell it how wide
     the screen is.  We used to do this by just always feeding
     `program' through sprintf() and setting the default value to
     "xscreensaver-text --cols %d", but that makes things blow up
     if someone ever uses a --program that includes a % anywhere.
   */
  len = 17; /* strlen("xscreensaver-text") */
  if (oprogram_size >= len &&
    !memcmp (oprogram, "xscreensaver-text", len) &&
    (oprogram[len] == ' ' || !oprogram[len]))
    {
      /* strstr is sloppy here. Technically, we should be parsing the command
         line to identify flags and their arguments. This will blow up if one
         of those pesky end users could set .textLiteral to "--cols".
       */
      if (d->char_w && !strstr (oprogram, "--cols "))
        sprintf (s, " --cols %d", d->char_w);
      if (d->max_lines && !strstr (oprogram, "--lines "))
        sprintf (s, " --lines %d", d->max_lines);
      s += strlen(s);

# ifdef HAVE_COCOA
      /* Also special-case "xscreensaver-text" to specify the text content on
         the command line. defaults(1) on macOS doesn't know about the default
         screenhack resources that don't make it into the
         ~/Library/Preferences/ByHost/org.jwz.xscreensaver.*.plist.
       */

      char *text_mode_flag = " --date";
      char *value_res = NULL;
      char *text_mode = get_string_resource (d->dpy, "textMode", "String");

      if (text_mode)
        {
          if (!strcmp (text_mode, "1") || !strcmp (text_mode, "literal"))
            {
              text_mode_flag = " --text";
              value_res = "textLiteral";
            }
          else if (!strcmp (text_mode, "2") || !strcmp (text_mode, "file"))
            {
              text_mode_flag = " --file";
              value_res = "textFile";
            }
          else if (!strcmp (text_mode, "3") || !strcmp (text_mode, "url"))
            {
              text_mode_flag = " --url";
              value_res = "textURL";
            }
          else if (!strcmp (text_mode, "4") || !strcmp (text_mode, "program"))
            {
              text_mode_flag = " --program";
              value_res = "textProgram";
            }

          free (text_mode);
        }

      strcpy (s, text_mode_flag);
      s += strlen (s);

      if (value_res)
        {
          size_t old_s = s - cmd;
          char *value = get_string_resource (d->dpy, value_res, "");
          if (!value)
            value = strdup("");
          cmd = realloc(cmd, cmd_capacity + strlen(value) * 2);
          s = cmd + old_s;
          *s = ' ';
          ++s;
          s = escape_str(s, value);
          free(value);
        }
# endif /* HAVE_COCOA */
    }

  strcpy (s, " ) 2>&1");

# ifdef DEBUG
  fprintf (stderr, "%s: textclient: launch %s: %s\n", progname,
           (d->pty_p ? "pty" : "pipe"), cmd);
# endif

#ifdef HAVE_FORKPTY
  if (d->pty_p)
    {
      int fd;
      struct winsize ws;

      ws.ws_col = d->char_w;
      ws.ws_row = d->char_h;
      ws.ws_xpixel = d->pix_w;
      ws.ws_ypixel = d->pix_h;

      d->pipe = 0;

# ifdef HAVE_COCOA
      if (getenv ("MallocScribble"))
        /* This is here to stop me from wasting my time trying to answer
           this question the next time I forget about it. */
        fprintf (stderr, "%s: WARNING: forkpty hates 'Enable Guard Malloc'\n",
                 progname);
# endif

      if ((d->pid = forkpty(&fd, NULL, NULL, &ws)) < 0)
        {
          /* Unable to fork */
          sprintf (buf, "%.100s: forkpty", progname);
          perror (buf);
        }
      else if (!d->pid)
        {
          /* This is the child fork. */
          char *av[10];
          int i = 0;
          if (putenv ("TERM=vt100"))
            abort();
          av[i++] = "/bin/sh";
          av[i++] = "-c";
          av[i++] = cmd;
          av[i] = 0;
# ifdef DEBUG
          {
            int j;
            fprintf (stderr, "%s: textclient: execvp:", progname);
            for (j = 0; j < i; j++)
              fprintf (stderr, " %s", av[j]);
            fprintf (stderr, "\n");
          }
# endif
          execvp (av[0], av);
          sprintf (buf, "%.100s: %.100s", progname, oprogram);
          perror (buf);
          exit (1);
        }
      else
        {
          /* This is the parent fork. */
          if (d->pipe) abort();
          d->pipe = fdopen (fd, "r+");
          if (d->pipe_id) abort();
          d->pipe_id =
            XtAppAddInput (app, fileno (d->pipe),
                           (XtPointer) (XtInputReadMask | XtInputExceptMask),
                           subproc_cb, (XtPointer) d);
# ifdef DEBUG
          fprintf (stderr, "%s: textclient: pid = %d\n", progname, d->pid);
# endif
        }
    }
  else
#endif /* HAVE_FORKPTY */
    {
      /* don't mess up controlling terminal on "-pipe -program tcsh". */
      static int protected_stdin_p = 0;
      if (! protected_stdin_p) {
        fclose (stdin);
        open ("/dev/null", O_RDWR); /* re-allocate fd 0 */
        protected_stdin_p = 1;
      }

      if (d->pipe) abort();
      if ((d->pipe = popen (cmd, "r")))
        {
          if (d->pipe_id) abort();
          d->pipe_id =
            XtAppAddInput (app, fileno (d->pipe),
                           (XtPointer) (XtInputReadMask | XtInputExceptMask),
                           subproc_cb, (XtPointer) d);
# ifdef DEBUG
          fprintf (stderr, "%s: textclient: popen\n", progname);
# endif
        }
      else
        {
          sprintf (buf, "%.100s: %.100s", progname, cmd);
          perror (buf);
        }
    }

  free (cmd);
}


static void
relaunch_generator_timer (XtPointer closure, XtIntervalId *id)
{
  text_data *d = (text_data *) closure;
  /* if (!d->pipe_timer) abort(); */
  d->pipe_timer = 0;
# ifdef DEBUG
  fprintf (stderr, "%s: textclient: launch timer fired\n", progname);
# endif
  launch_text_generator (d);
}


static void
start_timer (text_data *d)
{
  XtAppContext app = XtDisplayToApplicationContext (d->dpy);

# ifdef DEBUG
  fprintf (stderr, "%s: textclient: relaunching in %d\n", progname,
           (int) d->subproc_relaunch_delay);
# endif
  if (d->pipe_timer)
    XtRemoveTimeOut (d->pipe_timer);
  d->pipe_timer =
    XtAppAddTimeOut (app, d->subproc_relaunch_delay,
                     relaunch_generator_timer,
                     (XtPointer) d);
}


static void
close_pipe (text_data *d)
{
  if (d->pid)
    {
# ifdef DEBUG
      fprintf (stderr, "%s: textclient: kill %d\n", progname, d->pid);
# endif
      kill (d->pid, SIGTERM);
    }
  d->pid = 0;

  if (d->pipe_id)
    XtRemoveInput (d->pipe_id);
  d->pipe_id = 0;

  if (d->pipe)
    {
# ifdef DEBUG
      fprintf (stderr, "%s: textclient: pclose\n", progname);
# endif
      pclose (d->pipe);
    }
  d->pipe = 0;


}


void
textclient_reshape (text_data *d,
                    int pix_w, int pix_h,
                    int char_w, int char_h,
                    int max_lines)
{
# if defined(HAVE_FORKPTY) && defined(TIOCSWINSZ)

  d->pix_w  = pix_w;
  d->pix_h  = pix_h;
  d->char_w = char_w;
  d->char_h = char_h;
  d->max_lines = max_lines;

# ifdef DEBUG
  fprintf (stderr, "%s: textclient: reshape: %dx%d, %dx%d\n", progname,
           pix_w, pix_h, char_w, char_h);
# endif

  if (d->pid && d->pipe)
    {
      /* Tell the sub-process that the screen size has changed. */
      struct winsize ws;
      ws.ws_col = char_w;
      ws.ws_row = char_h;
      ws.ws_xpixel = pix_w;
      ws.ws_ypixel = pix_h;
      ioctl (fileno (d->pipe), TIOCSWINSZ, &ws);
      kill (d->pid, SIGWINCH);
#  ifdef DEBUG
      fprintf (stderr, "%s: textclient: SIGWINCH\n", progname);
#  endif
    }
# endif /* HAVE_FORKPTY && TIOCSWINSZ */


  /* If we're running xscreensaver-text, then kill and restart it any
     time the window is resized so that it gets an updated --cols arg
     right away.  But if we're running something else, leave it alone.
   */
  if (!strcmp (d->program, "xscreensaver-text"))
    {
# ifdef DEBUG
      fprintf (stderr, "%s: textclient: reshape relaunch\n", progname);
# endif
      close_pipe (d);
      d->input_available_p = False;
      start_timer (d);
    }
}


text_data *
textclient_open (Display *dpy)
{
  text_data *d = (text_data *) calloc (1, sizeof (*d));

# ifdef DEBUG
  fprintf (stderr, "%s: textclient: init\n", progname);
# endif

  d->dpy = dpy;

  if (get_boolean_resource (dpy, "usePty", "UsePty"))
    {
# ifdef HAVE_FORKPTY
      d->pty_p = True;
# else
      fprintf (stderr,
               "%s: no pty support on this system; using a pipe instead.\n",
               progname);
# endif
    }

  d->subproc_relaunch_delay =
    get_integer_resource (dpy, "relaunchDelay", "Time");
  if (d->subproc_relaunch_delay < 1)
    d->subproc_relaunch_delay = 1;
  d->subproc_relaunch_delay *= 1000;


  d->meta_sends_esc_p = get_boolean_resource (dpy, "metaSendsESC", "Boolean");
  d->swap_bs_del_p    = get_boolean_resource (dpy, "swapBSDEL",    "Boolean");

  d->program = get_string_resource (dpy, "program", "Program");


# ifdef HAVE_FORKPTY
  /* Kludge for MacOS standalone mode: see OSX/SaverRunner.m. */
  {
    const char *s = getenv ("XSCREENSAVER_STANDALONE");
    if (s && *s && strcmp(s, "0"))
      {
        d->pty_p = 1;
        d->program = strdup (getenv ("SHELL"));
#  ifdef DEBUG
        fprintf (stderr, "%s: textclient: standalone: %s\n",
                 progname, d->program);
#  endif
      }
  }
# endif

  start_timer (d);

  return d;
}


void
textclient_close (text_data *d)
{
# ifdef DEBUG
  fprintf (stderr, "%s: textclient: free\n", progname);
# endif

  close_pipe (d);
  if (d->program)
    free (d->program);
  if (d->pipe_timer)
    XtRemoveTimeOut (d->pipe_timer);
  d->pipe_timer = 0;
  memset (d, 0, sizeof (*d));
  free (d);
}

int
textclient_getc (text_data *d)
{
  XtAppContext app = XtDisplayToApplicationContext (d->dpy);
  int ret = -1;

  if (XtAppPending (app) & (XtIMTimer|XtIMAlternateInput))
    XtAppProcessEvent (app, XtIMTimer|XtIMAlternateInput);

  if (d->out_buffer && *d->out_buffer)
    {
      ret = *d->out_buffer;
      d->out_buffer++;
    }
  else if (d->input_available_p && d->pipe)
    {
      unsigned char s[2];
      int n = read (fileno (d->pipe), (void *) s, 1);
      if (n > 0)
        ret = s[0];
      else              /* EOF */
        {
          if (d->pid)
            {
# ifdef DEBUG
              fprintf (stderr, "%s: textclient: waitpid %d\n",
                       progname, d->pid);
# endif
              waitpid (d->pid, NULL, 0);
              d->pid = 0;
            }

          close_pipe (d);

          if (d->out_column > 0)
            {
# ifdef DEBUG
              fprintf (stderr, "%s: textclient: adding blank line at EOF\n",
                       progname);
# endif
              d->out_buffer = "\r\n\r\n";
            }

          start_timer (d);
        }
      d->input_available_p = False;
    }

  if (ret == '\r' || ret == '\n')
    d->out_column = 0;
  else if (ret > 0)
    d->out_column++;

# ifdef DEBUG
  if (ret <= 0)
    fprintf (stderr, "%s: textclient: getc: %d\n", progname, ret);
  else if (ret < ' ')
    fprintf (stderr, "%s: textclient: getc: %03o\n", progname, ret);
  else
    fprintf (stderr, "%s: textclient: getc: '%c'\n", progname, (char) ret);
# endif

  return ret;
}


/* The interpretation of the ModN modifiers is dependent on what keys
   are bound to them: Mod1 does not necessarily mean "meta".  It only
   means "meta" if Meta_L or Meta_R are bound to it.  If Meta_L is on
   Mod5, then Mod5 is the one that means Meta.  Oh, and Meta and Alt
   aren't necessarily the same thing.  Icepicks in my forehead!
 */
static unsigned int
do_icccm_meta_key_stupidity (Display *dpy)
{
  unsigned int modbits = 0;
# ifndef HAVE_COCOA
  int i, j, k;
  XModifierKeymap *modmap = XGetModifierMapping (dpy);
  for (i = 3; i < 8; i++)
    for (j = 0; j < modmap->max_keypermod; j++)
      {
        int code = modmap->modifiermap[i * modmap->max_keypermod + j];
        KeySym *syms;
        int nsyms = 0;
        if (code == 0) continue;
        syms = XGetKeyboardMapping (dpy, code, 1, &nsyms);
        for (k = 0; k < nsyms; k++)
          if (syms[k] == XK_Meta_L || syms[k] == XK_Meta_R ||
              syms[k] == XK_Alt_L  || syms[k] == XK_Alt_R)
            modbits |= (1 << i);
        XFree (syms);
      }
  XFreeModifiermap (modmap);
# endif /* HAVE_COCOA */
  return modbits;
}


/* Returns a mask of the bit or bits of a KeyPress event that mean "meta".
 */
static unsigned int
meta_modifier (text_data *d)
{
  if (!d->meta_done_once)
    {
      /* Really, we are supposed to recompute this if a KeymapNotify
         event comes in, but fuck it. */
      d->meta_done_once = True;
      d->meta_mask = do_icccm_meta_key_stupidity (d->dpy);
# ifdef DEBUG
      fprintf (stderr, "%s: textclient: ICCCM Meta is 0x%08X\n",
               progname, d->meta_mask);
# endif
    }
  return d->meta_mask;
}


Bool
textclient_putc (text_data *d, XKeyEvent *k)
{
  KeySym keysym;
  unsigned char c = 0;
  XLookupString (k, (char *) &c, 1, &keysym, &d->compose);
  if (c != 0 && d->pipe)
    {
      if (!d->swap_bs_del_p) ;
      else if (c == 127) c = 8;
      else if (c == 8)   c = 127;

      /* If meta was held down, send ESC, or turn on the high bit. */
      if (k->state & meta_modifier (d))
        {
          if (d->meta_sends_esc_p)
            fputc ('\033', d->pipe);
          else
            c |= 0x80;
        }

      fputc (c, d->pipe);
      fflush (d->pipe);
      k->type = 0;  /* don't interpret this event defaultly. */

# ifdef DEBUG
      fprintf (stderr, "%s: textclient: putc '%c'\n", progname, (char) c);
# endif

      return True;
    }
  return False;
}

#endif /* !HAVE_IPHONE -- whole file */