New tag %ss() which lets you get a substring of another tag.

%ss(start, length, tag) - i.e %ss(0,1,%TL) will get the first letter of the current lines text.
use - for the length to get the rest of the tag (e.g %ss(1,-,%TL) will get everything after the first letter).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30500 a1c6a512-1295-4272-9138-f99709370657

lib/skin_parser/tag_table.c

@@ -236,7 +236,8 @@ static const struct tag_info legal_tags[] =
     { SKIN_TOKEN_VAR_SET,               "vs",   "SSI|I", SKIN_REFRESH_STATIC },
     { SKIN_TOKEN_VAR_GETVAL,            "vg",   "S", SKIN_REFRESH_DYNAMIC },
     { SKIN_TOKEN_VAR_TIMEOUT,           "vl",   "S|D", SKIN_REFRESH_DYNAMIC },
-    
+
+    { SKIN_TOKEN_SUBSTRING,             "ss",   "IiT", SKIN_REFRESH_DYNAMIC },
     { SKIN_TOKEN_UNKNOWN,                ""   , "", 0 }
     /* Keep this here to mark the end of the table */
 };

lib/skin_parser/tag_table.h

@@ -279,6 +279,8 @@ enum skin_token_type {
     SKIN_TOKEN_VAR_SET,
     SKIN_TOKEN_VAR_GETVAL,
     SKIN_TOKEN_VAR_TIMEOUT,
+
+    SKIN_TOKEN_SUBSTRING,
 };
 
 /*