From a3a5db1311aff0c8d432eca6ed70dfbe9696e33c Mon Sep 17 00:00:00 2001
From: Nipunn Koorapati <nipunn@dropbox.com>
Date: Mon, 13 Jul 2020 00:59:29 +0000
Subject: [PATCH] Add comments and limit to standard colors

---
 watch.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/watch.c b/watch.c
index cfe191be..51cc880f 100644
--- a/watch.c
+++ b/watch.c
@@ -137,23 +137,34 @@ static void init_ansi_colors(void)
 }
 
 
-static int color_escape_sequence(char** escape_sequence) {
+static int process_ansi_color_escape_sequence(char** escape_sequence) {
+    // process SGR ANSI color escape sequence
+    // Eg 8-bit
+    // 38;5;⟨n⟩  (set fg color to n)
+    // 48;5;⟨n⟩  (set bg color to n)
+    //
+    // Eg 24-bit (not yet implemented)
+    // ESC[ 38;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB foreground color
+    // ESC[ 48;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB background color
     int num;
 
     if ((*escape_sequence)[0] != ';')
         return 0; /* not understood */
 
     if ((*escape_sequence)[1] == '5') {
-        // 8 bit!
+        // 8 bit! ANSI specifies a predefined set of 256 colors here.
         if ((*escape_sequence)[2] != ';')
             return 0; /* not understood */
         num = strtol((*escape_sequence) + 3, escape_sequence, 10);
         if (num >= 0 && num <= 7) {
+            // 0-7 are standard colors  same as SGR 30-37
             return num + 1;
-        } else if (num >= 8 && num <= 15) {
-            // Bright intensity colors. Show them as normal for simplicty of impl
-            return num - 8 + 1;
         }
+
+        // Remainder aren't yet implemented
+        // 8- 15:  high intensity colors (as in ESC [ 90–97 m)
+        // 16-231:  6 × 6 × 6 cube (216 colors): 16 + 36 × r + 6 × g + b (0 ≤ r, g, b ≤ 5)
+        // 232-255:  grayscale from black to white in 24 steps
     }
 
     return 0; /* not understood */
@@ -209,7 +220,7 @@ static int set_ansi_attribute(const int attrib, char** escape_sequence)
 		attributes &= ~A_REVERSE;
 		break;
     case 38:
-        fg_col = color_escape_sequence(escape_sequence);
+        fg_col = process_ansi_color_escape_sequence(escape_sequence);
         if (fg_col == 0) {
             return 0; /* not understood */
         }
@@ -218,7 +229,7 @@ static int set_ansi_attribute(const int attrib, char** escape_sequence)
 		fg_col = 0;
 		break;
     case 48:
-        bg_col = color_escape_sequence(escape_sequence);
+        bg_col = process_ansi_color_escape_sequence(escape_sequence);
         if (bg_col == 0) {
             return 0; /* not understood */
         }