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/* SVGATextMode -- An SVGA textmode manipulation/enhancement tool
*
* Copyright (C) 1995-1998 Koen Gadeyne
*
* 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 of the License, 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.
*/
/***
*** wait_vsync.c: non-blocking V-blanking wait routine (doesn't hang when no VSYNC)
*** waits until start of V-blanking interval.
***/
#include <stdio.h>
#ifndef WIN
# include <values.h>
#endif
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include "misc.h"
#include "vga_prg.h"
#include "wait_vsync.h"
#include "messages.h"
bool vtimeout=FALSE; /* will be set TRUE if VSYNC times out */
void nop()
{
}
/* alarm fuction for when probe times out on too slow V-sync */
void badsync(int signal)
{
PWARNING(("Slow sync. Possibly no, or very slow clock (vertical refresh < 1 Hz).\n"));
vtimeout=TRUE;
}
int safe_wait_vsync()
{
/* check if vertical refresh is "reasonable" , and avoid "hangup" when something is really wrong */
vtimeout=FALSE;
PDEBUG(("Checking for Slow Sync...\n"));
signal(SIGALRM, badsync);
alarm(2);
wait_vblk;
alarm(0);
signal(SIGALRM, SIG_DFL);
return(!vtimeout);
}
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