/* signals.c -- Install and maintain Info signal handlers. */

/* This file is part of GNU Info, a program for reading online documentation
   stored in Info format.

   Copyright (C) 1993 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   Written by Brian Fox (bfox@ai.mit.edu). */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "info.h"
#include "signals.h"

/* **************************************************************** */
/*								    */
/*		Pretending That We Have POSIX Signals		    */
/*								    */
/* **************************************************************** */

#if !defined (_POSIX_VERSION)
/* Perform OPERATION on NEWSET, perhaps leaving information in OLDSET. */
static void
sigprocmask (operation, newset, oldset)
     int operation, *newset, *oldset;
{
  switch (operation)
    {
    case SIG_UNBLOCK:
#if defined (HAVE_SIGSETMASK)
      sigsetmask (sigblock (0) & ~(*newset));
#endif /* HAVE_SIGSETMASK */
      break;

    case SIG_BLOCK:
      *oldset = sigblock (*newset);
      break;

    case SIG_SETMASK:
#if defined (HAVE_SIGSETMASK)
      sigsetmask (*newset);
#endif /* HAVE_SIGSETMASK */
      break;

    default:
      abort ();
    }
}
#endif /* !_POSIX_VERSION */

/* **************************************************************** */
/*								    */
/*		    Signal Handling for Info			    */
/*								    */
/* **************************************************************** */

typedef void SigHandlerType;
typedef SigHandlerType SigHandler ();

static SigHandlerType info_signal_handler ();
static SigHandler *old_TSTP, *old_TTOU, *old_TTIN;
static SigHandler *old_WINCH, *old_INT;

void
initialize_info_signal_handler ()
{
#if defined (SIGTSTP)
  old_TSTP = (SigHandler *) signal (SIGTSTP, info_signal_handler);
  old_TTOU = (SigHandler *) signal (SIGTTOU, info_signal_handler);
  old_TTIN = (SigHandler *) signal (SIGTTIN, info_signal_handler);
#endif /* SIGTSTP */

#if defined (SIGWINCH)
  old_WINCH = (SigHandler *) signal (SIGWINCH, info_signal_handler);
#endif

#if defined (SIGINT)
  old_INT = (SigHandler *) signal (SIGINT, info_signal_handler);
#endif
}

void
clear_info_signal_handler ()
{
#if defined (SIGTSTP)
  signal (SIGTSTP, old_TSTP);
  signal (SIGTTOU, old_TTOU);
  signal (SIGTTIN, old_TTIN);
#endif /* SIGTSTP */

#if defined (SIGWINCH)
  signal (SIGWINCH, old_WINCH);
#endif

#if defined (SIGINT)
  signal (SIGINT, old_INT);
#endif
}

static void
redisplay_after_signal ()
{
  terminal_clear_screen ();
  display_clear_display (the_display);
  window_mark_chain (windows, W_UpdateWindow);
  display_update_display (windows);
  display_cursor_at_point (active_window);
  fflush (stdout);
}

static SigHandlerType
info_signal_handler (sig)
     int sig;
{
  SigHandler **old_signal_handler;

  switch (sig)
    {
#if defined (SIGTSTP)
    case SIGTSTP:
    case SIGTTOU:
    case SIGTTIN:
#endif
#if defined (SIGINT)
    case SIGINT:
#endif
      {
#if defined (SIGTSTP)
	if (sig == SIGTSTP)
	  old_signal_handler = &old_TSTP;
	else if (sig == SIGTTOU)
	  old_signal_handler = &old_TTOU;
	else if (sig == SIGTTIN)
	  old_signal_handler = &old_TTIN;
#endif /* SIGTSTP */
#if defined (SIGINT)
	else if (sig == SIGINT)
	  old_signal_handler = &old_INT;
#endif

	/* For stop signals, restore the terminal IO, leave the cursor
	   at the bottom of the window, and stop us. */
	terminal_goto_xy (0, screenheight - 1);
	terminal_clear_to_eol ();
	fflush (stdout);
	terminal_unprep_terminal ();
 	UNBLOCK_SIGNAL (sig);
	signal (sig, *old_signal_handler);
	kill (getpid (), sig);

	/* The program is returning now.  Restore our signal handler,
	   turn on terminal handling, redraw the screen, and place the
	   cursor where it belongs. */
	
	terminal_prep_terminal ();
	*old_signal_handler = (SigHandler *) signal (sig, info_signal_handler);
	redisplay_after_signal ();
	fflush (stdout);
      }
      break;

#if defined (SIGWINCH)
    case SIGWINCH:
      {
	/* Turn off terminal IO, tell our parent that the window has changed,
	   then reinitialize the terminal and rebuild our windows. */
	old_signal_handler = &old_WINCH;
	terminal_goto_xy (0, 0);
	fflush (stdout);
	terminal_unprep_terminal ();
	signal (sig, *old_signal_handler);
 	UNBLOCK_SIGNAL (sig);
	kill (getpid (), sig);

	/* After our old signal handler returns... */
	terminal_get_screen_size ();
	terminal_prep_terminal ();
	display_initialize_display (screenwidth, screenheight);
	window_new_screen_size (screenwidth, screenheight, (VFunction *)NULL);
	*old_signal_handler = (SigHandler *) signal (sig, info_signal_handler);
	redisplay_after_signal ();
      }
      break;
#endif /* SIGWINCH */
    }
}