Re: strange Fselect/Finstat behaviour...

[Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>]

This is how i'm interpreting the situation: The keyboard is checked
periodically for the control characters as defined by the tty
settings.  Without MiNT, ^C/^S/^Q is only checked when a program
explicitly reads a character in non-raw mode.  To maintain
compatibility with old programs which uses Crawcin when they don't
want to be killed, there is a flag in the tty settings (TS_COOKED) to
record how the terminal was last read.  If it was last read using RAW
mode, the check for control characters is effectively disabled, and it
is enabled again when reading in COOKED mode.  The problem is that you
don't know how a non-mint-aware program wants to handle ^C/^S until it
actually reads the terminal.

Now when using Fread() on a terminal that is set via ioctl() to RAW
mode, the TS_COOKED flag is cleared before any character arrives
(unless you're typing fast enough). On the other hand, when using
Finstat() or Fselect(), the control character arrives before the
terminal is read, and the state reflects the setting of the terminal
at the time the last character was read.

Try the patch below: if the terminal is configured with TIOCSETP, the
flag TS_COOKED will now be updated immediately, under the assumption
that a program that uses Fcntl() should be able to handle keyboard
signals gracefully.  This will slightly change the effect of ^C/^S
when a non-mint-aware program is started after a mint-aware program
that reads the terminal in RAW mode.

--- orig/tty.c	Fri Jun 25 22:24:58 1993
+++ tty.c	Mon Jan  3 20:01:16 1994
@@ -483,6 +483,11 @@
 	case TIOCSETP:
 		sg = (struct sgttyb *)arg;
 		tty->sg = *sg;
+		/* set the tty state for checking control characters */
+		if (sg->sg_flags & T_RAW)
+		  tty->state &= ~TS_COOKED;
+		else
+		  tty->state |= TS_COOKED;
 	/* set baud rates */
 		baud = tosbaud(sg->sg_ispeed);
 		(*f->dev->ioctl)(f, TIOCIBAUD, &baud);