tweaks: use meaningful names instead of puzzling values

Suggested-by: Brand Huntsman <alpha@qzx.com>

src/color.c

@@ -60,9 +60,9 @@ void set_colorpairs(void)
 		colortype *combo = color_combo[i];
 
 		if (combo != NULL) {
-			if (combo->fg == -1 && !using_defaults)
+			if (combo->fg == USE_THE_DEFAULT && !using_defaults)
 				combo->fg = COLOR_WHITE;
-			if (combo->bg == -1 && !using_defaults)
+			if (combo->bg == USE_THE_DEFAULT && !using_defaults)
 				combo->bg = COLOR_BLACK;
 			init_pair(i + 1, combo->fg, combo->bg);
 			interface_color_pair[i] = COLOR_PAIR(i + 1) | A_BANDAID |
@@ -125,10 +125,10 @@ void color_init(void)
 		foreground = ink->fg;
 		background = ink->bg;
 
-		if (foreground == -1 && !using_defaults)
+		if (foreground == USE_THE_DEFAULT && !using_defaults)
 			foreground = COLOR_WHITE;
 
-		if (background == -1 && !using_defaults)
+		if (background == USE_THE_DEFAULT && !using_defaults)
 			background = COLOR_BLACK;
 
 		init_pair(ink->pairnum, foreground, background);

src/nano.h

@@ -142,6 +142,11 @@
 #define REPLACING 1
 #define INREGION  2
 
+#ifdef ENABLE_COLOR
+#define USE_THE_DEFAULT -1
+#define BAD_COLOR -2
+#endif
+
 /* Enumeration types. */
 typedef enum {
 	NIX_FILE, DOS_FILE, MAC_FILE

src/rcfile.c

@@ -603,10 +603,10 @@ short color_to_short(const char *colorname, bool *bright)
 	else if (strcasecmp(colorname, "black") == 0)
 		return COLOR_BLACK;
 	else if (strcasecmp(colorname, "normal") == 0)
-		return -1;
+		return USE_THE_DEFAULT;
 
 	rcfile_error(N_("Color \"%s\" not understood"), colorname);
-	return -2;
+	return BAD_COLOR;
 }
 
 /* Parse the color name (or pair of color names) in the given string.
@@ -621,18 +621,18 @@ bool parse_color_names(char *combostr, short *fg, short *bg, bool *bright)
 			rcfile_error(N_("A background color cannot be bright"));
 			return FALSE;
 		}
-		if (*bg == -2)
+		if (*bg == BAD_COLOR)
 			return FALSE;
 		*comma = '\0';
 	} else
-		*bg = -1;
+		*bg = USE_THE_DEFAULT;
 
 	if (comma != combostr) {
 		*fg = color_to_short(combostr, bright);
-		if (*fg == -2)
+		if (*fg == BAD_COLOR)
 			return FALSE;
 	} else
-		*fg = -1;
+		*fg = USE_THE_DEFAULT;
 
 	return TRUE;
 }