Support xterm 256 color

README.md

@@ -60,7 +60,7 @@ It runs smoothly on the Pi, [Termux](https://www.youtube.com/watch?v=AbaauM7gUJw
 
 - Frugal
   - Typically needs less than 3.5MB resident memory
-  - Works with 8-bit colors
+  - Works with 8 colors (and xterm 256 colors)
   - Disk-IO sensitive (few disk reads and writes)
   - No FPU usage (all integer maths, even for file size)
   - Minimizes screen refresh with fast line redraws

nnn.1

@@ -408,9 +408,18 @@ separated by \fI;\fR:
 .Pp
 \fBNNN_COLORS:\fR string of color codes for each context, e.g.:
 .Bd -literal
+    # 8 color codes
+    # codes: 0-black, 1-red, 2-green, 3-yellow, 4-blue (default), 5-magenta, 6-cyan, 7-white
     export NNN_COLORS='1234'
 
-    codes: 0-black, 1-red, 2-green, 3-yellow, 4-blue (default), 5-magenta, 6-cyan, 7-white
+    # xterm 256 color codes (in hex)
+    # codes: https://upload.wikimedia.org/wikipedia/commons/1/15/Xterm_256color_chart.svg
+    export NNN_COLORS='#0a1b2c3d'
+
+    # both (256 followed by 8 as fallback, separated by ';')
+    export NNN_COLORS='#0a1b2c3d;1234'
+
+    NOTE: If only 256 colors are specified and the terminal doesn't support, default (4-blue) is used.
 .Ed
 .Pp
 \fBNNN_ARCHIVE:\fR archive types to be handled silently (default: bzip2, (g)zip, tar).

src/nnn.c

@@ -757,6 +757,21 @@ static char *xitoa(uint val)
 	return &ascbuf[++i];
 }
 
+/* Return the integer value of a char representing HEX */
+static uchar xchartohex(uchar c)
+{
+	if (xisdigit(c))
+		return c - '0';
+
+	if (c >= 'a' && c <= 'f')
+		return c - 'a' + 10;
+
+	if (c >= 'A' && c <= 'F')
+		return c - 'A' + 10;
+
+	return c;
+}
+
 /*
  * Source: https://elixir.bootlin.com/linux/latest/source/arch/alpha/include/asm/bitops.h
  */
@@ -1571,18 +1586,51 @@ static bool initcurses(void *oldmask)
 	char *colors = getenv(env_cfg[NNN_COLORS]);
 
 	if (colors || !getenv("NO_COLOR")) {
+		uint *pcode;
+		char ch;
+		bool ext = FALSE;
+
 		start_color();
 		use_default_colors();
 
+		if (colors && *colors == '#') {
+			if (COLORS >= 256) {
+				++colors;
+				ext = TRUE;
+
+				/*
+				 * If fallback colors are specified, set the separator
+				 * to NULL so we don't interpret separator and fallback
+				 * if fewer than CTX_MAX xterm 256 colors are specified.
+				 */
+				char *sep = strchr(colors, ';');
+				if (sep)
+					*sep = '\0';
+			} else
+				/* Check if 8 colors fallback is appended */
+				colors = strchr(colors, ';') + 1;
+		}
+
 		/* Get and set the context colors */
 		for (uchar i = 0; i <  CTX_MAX; ++i) {
-			if (colors && *colors) {
-				g_ctx[i].color = (*colors < '0' || *colors > '7') ? 4 : *colors - '0';
-				++colors;
-			} else
-				g_ctx[i].color = 4;
+			pcode = &g_ctx[i].color;
 
-			init_pair(i + 1, g_ctx[i].color, -1);
+			if (colors && *colors) {
+				if (ext) {
+					ch = *colors;
+					if (*++colors) {
+						*pcode = (16 * xchartohex(ch)) + xchartohex(*colors);
+						++colors;
+					} else
+						*pcode = xchartohex(ch);
+				} else {
+					*pcode = (*colors < '0' || *colors > '7') ? 4 : *colors - '0';
+					++colors;
+				}
+			} else
+				*pcode = 4;
+
+			init_pair(i + 1, *pcode, -1);
 		}
 	}
 
@@ -2217,21 +2265,6 @@ static int xstrverscasecmp(const char * const s1, const char * const s2)
 
 static int (*namecmpfn)(const char * const s1, const char * const s2) = &xstricmp;
 
-/* Return the integer value of a char representing HEX */
-static char xchartohex(char c)
-{
-	if (xisdigit(c))
-		return c - '0';
-
-	if (c >= 'a' && c <= 'f')
-		return c - 'a' + 10;
-
-	if (c >= 'A' && c <= 'F')
-		return c - 'A' + 10;
-
-	return c;
-}
-
 static char * (*fnstrstr)(const char *haystack, const char *needle) = &strcasestr;
 #ifdef PCRE
 static const unsigned char *tables;