skin_engine: Allow negative numbers for the start offset in %ss

i.e %ss(-1, -, %ia) will get the last letter in the %ia tag

Change-Id: I6b2764d30c072b549e7424fc6e847ec48850b46a

1 files changed, 4 insertions, 1 deletions

diff --git a/apps/gui/skin_engine/skin_tokens.c b/apps/gui/skin_engine/skin_tokens.c
index 29ddad4c5b..1bb5b8e555 100644
--- a/apps/gui/skin_engine/skin_tokens.c
+++ b/apps/gui/skin_engine/skin_tokens.c
@@ -927,7 +927,10 @@ const char *get_token_value(struct gui_wps *gwps,
                 if (utf8_len < ss->start)
                     return NULL;
 
-                start_byte = utf8seek(token_val, ss->start);
+                if (ss->start < 0)
+                    start_byte = utf8seek(token_val, ss->start + utf8_len);
+                else
+                    start_byte = utf8seek(token_val, ss->start);
 
                 if (ss->length < 0 || (ss->start + ss->length) > utf8_len)
                     end_byte = strlen(token_val);