Always set explicit HarfBuzz buffer direction

If no direction was given by the caller, I assume the text will be drawn
left to right, if this is not the case then callers must provide
sensible direction. Letting HarfBuzz guess the direction is not
appropriate since shaping and drawing must use the same direction.

Also move hb_buffer_guess_segment_properties() call to the end, so it
only guessing unset properties, until we completely get rid of it.

diff --git a/src/ftfont.c b/src/ftfont.c
index 5a8adfdb24ccb9de974a1f376f9e32e6456308f3..c2662875f8bde4838c73be48ba68e7cb139c6c41 100644 (file)
--- a/src/ftfont.c
+++ b/src/ftfont.c
@@ -2836,23 +2836,20 @@ ftfont_shape_by_hb (Lisp_Object lgstring, FT_Face ft_face, hb_font_t *hb_font,
   hb_buffer_set_content_type (hb_buffer, HB_BUFFER_CONTENT_TYPE_UNICODE);
   hb_buffer_set_cluster_level (hb_buffer, HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS);
 
-  /* Set the default properties for when they cannot be determined
-     below.  */
-  hb_buffer_guess_segment_properties (hb_buffer);
-  hb_direction_t dir = HB_DIRECTION_INVALID;
+  /* If the caller didn't provide a meaningful DIRECTION, default to L2R. */
+  hb_direction_t dir = HB_DIRECTION_LTR;
   if (EQ (direction, QL2R))
     dir = HB_DIRECTION_LTR;
   else if (EQ (direction, QR2L))
     dir = HB_DIRECTION_RTL;
-  /* If the caller didn't provide a meaningful DIRECTION, let HarfBuzz
-     guess it.  */
-  if (dir != HB_DIRECTION_INVALID)
-    hb_buffer_set_direction (hb_buffer, dir);
+  hb_buffer_set_direction (hb_buffer, dir);
+
   /* Leave the script determination to HarfBuzz, until Emacs has a
      better idea of the script of LGSTRING.  FIXME. */
 #if 0
   hb_buffer_set_script (hb_buffer, XXX);
 #endif
+
   /* FIXME: This can only handle the single global language, which
      normally comes from the locale.  In addition, if
      current-iso639-language is a list, we arbitrarily use the first
@@ -2869,6 +2866,10 @@ ftfont_shape_by_hb (Lisp_Object lgstring, FT_Face ft_face, hb_font_t *hb_font,
                                                       SBYTES (lang_str)));
     }
 
+  /* Guess the default properties for when they cannot be determined
+     above. FIXME: drop once script handling is fixed above. */
+  hb_buffer_guess_segment_properties (hb_buffer);
+
   if (!hb_shape_full (hb_font, hb_buffer, NULL, 0, NULL))
     return Qnil;