Colors: supports @<color-index>

CHANGELOG.md

@@ -14,6 +14,9 @@ Features:
 * Improves xterm font detection by checking `xterm.vt100.faceName` (TerminalFont, Linux)
 * Supports secure boot detection (Bootmgr, macOS)
 * Supports DPI scale factor detection on Windows 7 (Display, Windows)
+* Supports xterm 256 color codes in color configuration
+    * In `display.color`: "@<color-index>" (e.g., "@34" for color index 34)
+    * In `format` strings: "#@<color-index>" (e.g., "#@34" for color index 34)
 * Improves uptime accuracy on Windows 10+ (Uptime, Windows)
 
 Bugfixes:

src/common/impl/option.c

@@ -166,6 +166,22 @@ void ffOptionParseColorNoClear(const char* value, FFstrbuf* buffer)
                 exit(479);
             }
         }
+        else if (value[0] == '@')
+        {
+            // Xterm 256 color
+            ++value;
+            char* pend = NULL;
+            uint32_t color = (uint32_t) strtoul(value, &pend, 10);
+            if (pend == value || color > 255) {
+                fprintf(stderr, "Error: invalid 256 color code found: %s\n", value);
+                exit(479);
+            }
+
+            ffStrbufAppendS(buffer, FF_COLOR_FG_256);
+            ffStrbufAppendUInt(buffer, color);
+            value = pend;
+            continue;
+        }
         else if (value[0] == '#')
         {
             // RGB color

tests/color.c

@@ -44,6 +44,11 @@ int main(void)
         VERIFY("#123456", "38;2;18;52;86");
         VERIFY("#abc", "38;2;170;187;204");
 
+        // xterm 256 color codes
+        VERIFY("@0", "38;5;0");
+        VERIFY("@1", "38;5;1");
+        VERIFY("@255", "38;5;255");
+
         VERIFY("bold_#ff00ff", "1;38;2;255;0;255");
         VERIFY("underline_#123", "4;38;2;17;34;51");