sh_winsize(): minor rethink (re: f1c8ecc, 667034f, 1dd7e01)

If astwinsize cannot obtain the terminal window size, then it is`
better not to set the LINES and COLUMNS variables at all, instead
of setting default values.

However, do guarantee that the internal sh.rows and sh.columns
variables always have usable values, falling back to 24x80 if we
have no alternative.

Author: McDutchie

src/cmd/ksh93/sh/fault.c

@@ -202,18 +202,20 @@ void	sh_winsize(void)
 	int		lines, columns;
 	int32_t		i;
 	astwinsize(2,&lines,&columns);
-	if (lines <= 0 || lines > USHRT_MAX || columns <= 0 || columns > USHRT_MAX)
-		lines = 24, columns = 80;
+	if (lines < 0 || lines > USHRT_MAX)
+		lines = 0;
+	if (columns < 0 || columns > USHRT_MAX)
+		columns = 0;
 	/*
 	 * Update LINES and COLUMNS only when the values changed; this makes
 	 * LINES.set and COLUMNS.set shell discipline functions more useful.
 	 */
-	if ((lines != sh.lines || nv_isnull(LINES)) && (i = lines))
+	if (lines && (lines != sh.lines || nv_isnull(LINES)) && (i = lines))
 	{
 		nv_putval(LINES, (char*)&i, NV_INT32|NV_RDONLY);
 		sh.lines = lines;
 	}
-	if ((columns != sh.columns || nv_isnull(COLUMNS)) && (i = columns))
+	if (columns && (columns != sh.columns || nv_isnull(COLUMNS)) && (i = columns))
 	{
 		nv_putval(COLUMNS, (char*)&i, NV_INT32|NV_RDONLY);
 		sh.columns = columns;

src/cmd/ksh93/sh/io.c

@@ -2429,7 +2429,6 @@ static int subexcept(Sfio_t* sp,int mode, void *data, Sfdisc_t* handle)
 	return -1;
 }
 
-#define NROW    15      /* number of rows before going to multi-columns */
 #define LBLSIZ	3	/* size of label field and interfield spacing */
 /*
  * print a list of arguments in columns
@@ -2440,7 +2439,7 @@ void	sh_menu(Sfio_t *outfile,int argn,char *argv[])
 	char **arg;
 	int nrow, ncol=1, ndigits=1;
 	int fldsize, wsize = ed_window();
-	nrow = sh.lines ? (2 * (sh.lines / 3) + 1) : NROW;
+	nrow = 2 * (sh.lines / 3) + 1;	/* number of rows before going to multi-columns */
 	for(i=argn;i >= 10;i /= 10)
 		ndigits++;
 	if(argn < nrow)

src/cmd/ksh93/sh/main.c

@@ -316,6 +316,10 @@ int sh_main(int ac, char *av[], Shinit_f userinit)
 		fixargs(sh.st.dolv,1);
 	}
 	sh_winsize();
+	if(!sh.columns)
+		sh.columns = 80;
+	if(!sh.lines)
+		sh.lines = 24;
 	if(sh_isoption(SH_INTERACTIVE))
 	{
 		sh_onstate(SH_INTERACTIVE);