Support plotting with mutibyte characters

The options -c, -e and -E only support ASCII characters. Make them
support multibyte characters too, as box drawing and block elements can
make nice plotting glyphs.

This requires wide character support from the "ncursesw" version of the
ncurses library. Only characters supported by the user's locale can be
used, which includes the full Unicode repertoire on UTF-8 locales.

As the wide character API of ncurses does not support ACS characters,
the default plotting character on locales lacking mutibyte support is
now "|" (U+007C vertical line).

Makefile

@@ -2,7 +2,7 @@ DESTDIR   ?=
 PREFIX    ?= /usr/local
 MANPREFIX ?= $(PREFIX)/man
 CFLAGS += -Wall -Wextra
-LDLIBS += `pkg-config --libs ncurses 2>/dev/null || echo '-lcurses -ltinfo'`
+LDLIBS += `pkg-config --libs ncursesw 2>/dev/null || echo '-lcursesw -ltinfo'`
 torture: LDLIBS = -lm
 
 all: ttyplot

ttyplot.c

@@ -5,12 +5,14 @@
 // Apache License 2.0
 //
 
+#define _XOPEN_SOURCE 500  // Get ncurses wchar_t support from SUSv2 (UNIX 98)
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <float.h>
 #include <time.h>
+#include <locale.h>
 #include <ncurses.h>
 #include <signal.h>
 #include <errno.h>
@@ -45,7 +47,7 @@
 #endif
 
 sigset_t sigmsk;
-chtype plotchar, max_errchar, min_errchar;
+cchar_t plotchar, max_errchar, min_errchar;
 time_t t1,t2,td;
 struct tm *lt;
 double max=FLT_MIN;
@@ -121,19 +123,26 @@ void draw_axes(int h, int ph, int pw, double max, double min, char *unit) {
     mvaddch(h-3, 2, T_LLCR);
 }
 
-void draw_line(int x, int ph, int l1, int l2, chtype c1, chtype c2, chtype hce, chtype lce) {
+void draw_line(int x, int ph, int l1, int l2, cchar_t *c1, cchar_t *c2, cchar_t *hce, cchar_t *lce) {
+    static cchar_t space = {
+        .attr = A_REVERSE,
+        .chars = {' ', '\0'}
+    };
+    cchar_t c1r = *c1, c2r = *c2;
+    c1r.attr |= A_REVERSE;
+    c2r.attr |= A_REVERSE;
     if(l1 > l2) {
-        mvvline(ph+1-l1, x, c1, l1-l2 );
-        mvvline(ph+1-l2, x, c2|A_REVERSE, l2 );
+        mvvline_set(ph+1-l1, x, c1, l1-l2 );
+        mvvline_set(ph+1-l2, x, &c2r, l2 );
     } else if(l1 < l2) {
-        mvvline(ph+1-l2, x, (c2==hce || c2==lce) ? c2|A_REVERSE : ' '|A_REVERSE,  l2-l1 );
-        mvvline(ph+1-l1, x, c1|A_REVERSE, l1 );
+        mvvline_set(ph+1-l2, x, (c2==hce || c2==lce) ? &c2r : &space,  l2-l1 );
+        mvvline_set(ph+1-l1, x, &c2r, l1 );
     } else {
-        mvvline(ph+1-l2, x, c2|A_REVERSE, l2 );
+        mvvline_set(ph+1-l2, x, &c2r, l2 );
     }
 }
 
-void plot_values(int ph, int pw, double *v1, double *v2, double max, double min, int n, chtype pc, chtype hce, chtype lce, double hm) {
+void plot_values(int ph, int pw, double *v1, double *v2, double max, double min, int n, cchar_t *pc, cchar_t *hce, cchar_t *lce, double hm) {
     int i;
     int x=3;
     max-=min;
@@ -206,7 +215,7 @@ void paint_plot(void) {
     asctime_r(lt, ls);
     mvaddstr(height-2, width-strlen(ls), ls);
 
-    mvvline(height-2, 5, plotchar|A_NORMAL, 1);
+    mvvline_set(height-2, 5, &plotchar, 1);
     mvprintw(height-2, 7, "last=%.1f min=%.1f max=%.1f avg=%.1f %s ",  values1[n], min1, max1, avg1, unit);
     if(rate)
         printw(" interval=%llds", (long long int)td);
@@ -216,7 +225,7 @@ void paint_plot(void) {
         mvprintw(height-1, 7, "last=%.1f min=%.1f max=%.1f avg=%.1f %s   ",  values2[n], min2, max2, avg2, unit);
     }
 
-    plot_values(plotheight, plotwidth, values1, values2, max, hardmin, n, plotchar, max_errchar, min_errchar, hardmax);
+    plot_values(plotheight, plotwidth, values1, values2, max, hardmin, n, &plotchar, &max_errchar, &min_errchar, hardmax);
 
     draw_axes(height, plotheight, plotwidth, max, hardmin, unit);
 
@@ -258,9 +267,13 @@ int main(int argc, char *argv[]) {
     int show_ver;
     int show_usage;
 
-    plotchar=T_VLINE;
-    max_errchar='e';
-    min_errchar='v';
+    setlocale(LC_ALL, "");
+    if (MB_CUR_MAX > 1)            // if non-ASCII characters are supprted:
+        plotchar.chars[0]=0x2502;  // U+2502 box drawings light vertical
+    else
+        plotchar.chars[0]='|';     // U+007C vertical line
+    max_errchar.chars[0]='e';
+    min_errchar.chars[0]='v';
 
     cached_opterr = opterr;
     opterr=0;
@@ -310,16 +323,16 @@ int main(int argc, char *argv[]) {
                 break;
             case '2':
                 two=1;
-                plotchar='|';
+                plotchar.chars[0]='|';
                 break;
             case 'c':
-                plotchar=optarg[0];
+                mbtowc(&plotchar.chars[0], optarg, MB_CUR_MAX);
                 break;
             case 'e':
-                max_errchar=optarg[0];
+                mbtowc(&max_errchar.chars[0], optarg, MB_CUR_MAX);
                 break;
             case 'E':
-                min_errchar=optarg[0];
+                mbtowc(&min_errchar.chars[0], optarg, MB_CUR_MAX);
                 break;
             case 's':
                 softmax=atof(optarg);