From mboxrd@z Thu Jan  1 00:00:00 1970
From: lm at mcvoy.com (Larry McVoy)
Date: Thu, 26 Nov 2020 15:23:40 -0800
Subject: [TUHS] Seeking wisdom from Unix Greybeards
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Message-ID: <20201126232340.GE9609@mcvoy.com>

Did I miss a reason for the alternative?   Because if you add a caching
layer this approach has been working for me for decades.  I rewrote
dired in perl just because perl was everywhere and I could.  I've been
dragging the perl one around since at least 1990 and it worked for me
on pretty much any version of Unix.  I think MacOS isn't supported but
I'm sure it could be.

To avoid calling tput over and over again, I cached the output for each
terminal and then just evaled the cache which sets a bunch of variables
to the escapes I needed.

It performed just fine on 20mhz SPARCstations so I'm sort of wondering
why the solution for the problem isn't good enough.

# Dig out all the terminal info so we know the escape chars for this terminal.
sub terminal_init
{
	local($term) = "$ENV{'HOME'}/.term/$ENV{'TERM'}";
	local($i) = 0;

	$| = 1;
	@pids = ();
	$SIG{TERM} = sub { exit(0); };
	$SIG{PIPE} = 'IGNORE';
	# RedHat 5.0 seems to get this wrong somehow.
	#chop($tc_rows = `tput lines`);
	#chop($tc_cols = `tput cols`);
	open(STTY, "stty -a|");
	while (defined($_ = <STTY>)) {
		last if /rows = \d/ || /\d rows/ || /rows \d/;
	}
	close(STTY);
	#speed 9600 baud; rows 58; columns 80; line = 0;
	#speed 9600 baud; 47 rows; 80 columns;
	#rows = 66; columns = 80
	$tc_cols = 0;
	if (/rows (\d+); columns (\d+);/) {
		$tc_rows = $1;
		$tc_cols = $2;
	} elsif (/(\d+) rows; (\d+) columns;/) {
		$tc_rows = $1;
		$tc_cols = $2;
	} elsif (/rows = (\d+); columns = (\d+)/) {
		$tc_rows = $1;
		$tc_cols = $2;
	}
	if ($tc_cols == 0) {
		die "Can't get terminal settings.\n";
	}
	$half_of_screen = int($tc_rows / 2);

	# it's cached, go grab it.
	if (-f $term) {
		open(T, $term);
		@t = <T>;
		close(T);
		eval "@t";
		&ttyraw;
		return unless $i < $tc_rows;
	}

	print "Getting terminal info just this once and saving it...";
	mkdir("$ENV{'HOME'}/.term", 0755);
	open(T, ">$term");
	$tc_smcup = `tput smcup`;
	$tc_rmcup = `tput rmcup`;
	$tc_bold = `tput bold`;
	$tc_normal = `tput sgr0`;
	$tc_clear = `tput clear`;
	$tc_clreos = `tput ed`;
	$tc_clreol = `tput el`;

	if ($tc_cols < 60) {
		die "$0: needs 60 columns";
	}
	if (length($tc_clreos) == 0) {
		die "$0: needs clear to end of screen";
	}
	if (length($tc_clreol) == 0) {
		die "$0: needs clear to end of line";
	}

	print T "\$tc_smcup = \"$tc_smcup\";\n";
	print T "\$tc_rmcup = \"$tc_rmcup\";\n";
	print T "\$tc_bold = \"$tc_bold\";\n";
	print T "\$tc_normal = \"$tc_normal\";\n";
	print T "\$tc_clear = \"$tc_clear\";\n";
	print T "\$tc_clreol = \"$tc_clreol\";\n";
	print T "\$tc_clreos = \"$tc_clreos\";\n";

	for ($i = 0; $i < $tc_rows; ++$i) {
		$left[$i] = `tput cup $i 0`;
		print T '$left[' . "$i] = \"" . $left[$i] . "\";\n";
		if ($i < $half_of_screen) {
			$middle[$i] = `tput cup $i 44`;
			print T
			    '$middle[' . "$i] = \"" . $middle[$i] . "\";\n";
		}
	}
	print T '$i = ' . "$i;\n";
	close(T);
	print "done\n";
	&ttyraw;
}