* do *not* check the terminal size after each line processing,

only if we got a SIGWINCH -> interactive use speed-up on the
  slower boxen (slowness courtesy of otto@obsd)
* ^L (redraw line) now (always) checks window size; use this
  instead if required while editing the prompt; changes to the
  variables will still be propagated after the line is entered

edit.c

@@ -5,7 +5,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/edit.c,v 1.76 2007/01/12 10:18:20 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/edit.c,v 1.77 2007/01/14 01:09:08 tg Exp $");
 
 /* tty driver characters we are interested in */
 typedef struct {
@@ -129,7 +129,8 @@ x_read(char *buf, size_t len)
 		i = -1;		/* internal error */
 	x_mode(false);
 #if defined(TIOCGWINSZ) && defined(SIGWINCH)
-	check_sigwinch();
+	if (got_sigwinch)
+		check_sigwinch();
 #endif
 	return i;
 }
@@ -2235,9 +2236,9 @@ x_mv_begin(int c __unused)
 static int
 x_draw_line(int c __unused)
 {
+	check_sigwinch();
 	x_redraw(-1);
 	return KSTD;
-
 }
 
 /* Redraw (part of) the line.  If limit is < 0, the everything is redrawn

mksh.1

@@ -1,7 +1,7 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.73 2007/01/06 18:48:26 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.74 2007/01/14 01:09:09 tg Exp $
 .\" $OpenBSD: ksh.1,v 1.118 2006/11/30 08:47:58 jmc Exp $
 .\"
-.Dd January 6, 2007
+.Dd January 14, 2007
 .Dt MKSH 1
 .Os MirBSD
 .Sh NAME
@@ -4553,6 +4553,7 @@ word of the previous command is inserted at the cursor.
 The following character is taken literally rather than as an editing command.
 .It redraw: ^L
 Reprints the last line of the prompt string and the current input line.
+Also checks terminal size (columns and lines) as reported by stty for changes.
 .It Xo search-character-backward:
 .Op Ar n
 .No ^[^]