shaper: allow font encoding -1 for neutral base direction

1 files changed, 5 insertions, 2 deletions

diff --git a/libass/ass_shaper.c b/libass/ass_shaper.c
index b666ffb..89ea97a 100644
--- a/libass/ass_shaper.c
+++ b/libass/ass_shaper.c
@@ -714,15 +714,18 @@ FriBidiStrIndex *ass_shaper_reorder(ASS_Shaper *shaper, TextInfo *text_info)
 }
 
 /**
- * \brief Resolve a Windows font encoding number to a suitable
+ * \brief Resolve a Windows font charset number to a suitable
  * base direction. 177 and 178 are Hebrew and Arabic respectively, and
  * they map to RTL. Everything else maps to LTR for compatibility
- * reasons.
+ * reasons. The special value -1, which is not a legal Windows font charset
+ * number, can be used for autodetection.
  * \param enc Windows font encoding
  */
 FriBidiParType resolve_base_direction(int enc)
 {
     switch (enc) {
+        case -1:
+            return FRIBIDI_PAR_ON;
         case 177:
         case 178:
             return FRIBIDI_PAR_RTL;