Fix find_first_strong_char and implement Unicode 8.0 isolate corrections.

find_first_strong_char accepts 1 additional argument, which says to stop
at the PDI that matches the FSI where we started; callers changed.
Implemented suggested Unicode 8.0 corrections for type of RLI/LRI/PDI.

1 files changed, 57 insertions, 12 deletions

diff --git a/src/bidi.c b/src/bidi.c
index ca5b950d6d3..e01b77d0e96 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -1398,18 +1398,38 @@ bidi_find_paragraph_start (ptrdiff_t pos, ptrdiff_t pos_byte)
    bidi_paragraph_init to less than 10 ms even on slow machines.  */
 #define MAX_STRONG_CHAR_SEARCH 100000
 
+/* Starting from POS, find the first strong (L, R, or AL) character,
+   while skipping over any characters between an isolate initiator and
+   its matching PDI.  STOP_AT_PDI non-zero means stop at the PDI that
+   matches the isolate initiator at POS.  Return the bidi type of the
+   character where the search stopped.  Give up if after examining
+   MAX_STRONG_CHAR_SEARCH buffer or string positions no strong
+   character was found.  */
 static bidi_type_t
 find_first_strong_char (ptrdiff_t pos, ptrdiff_t bytepos, ptrdiff_t end,
                         ptrdiff_t *disp_pos, int *disp_prop,
                         struct bidi_string_data *string, struct window *w,
                         bool string_p, bool frame_window_p,
-                        ptrdiff_t *ch_len, ptrdiff_t *nchars)
+                        ptrdiff_t *ch_len, ptrdiff_t *nchars, bool stop_at_pdi)
 {
   ptrdiff_t pos1;
   bidi_type_t type;
   const unsigned char *s;
   int ch;
 
+  if (stop_at_pdi)
+    {
+      /* If STOP_AT_PDI is non-zero, we must have been called with FSI
+         at POS.  Get past it.  */
+#ifdef ENABLE_CHECKING
+      ch = bidi_fetch_char (pos, bytepos, disp_pos, disp_prop, string, w,
+                            frame_window_p, ch_len, nchars);
+      type = bidi_get_type (ch, NEUTRAL_DIR);
+      eassert (type == FSI /* || type == LRI || type == RLI */);
+#endif
+      pos += *nchars;
+      bytepos += *ch_len;
+    }
   ch = bidi_fetch_char_skip_isolates (pos, bytepos, disp_pos, disp_prop, string,
                                       w, frame_window_p, ch_len, nchars);
   type = bidi_get_type (ch, NEUTRAL_DIR);
@@ -1417,6 +1437,8 @@ find_first_strong_char (ptrdiff_t pos, ptrdiff_t bytepos, ptrdiff_t end,
   pos1 = pos;
   for (pos += *nchars, bytepos += *ch_len;
        bidi_get_category (type) != STRONG
+         /* If requested to stop at first PDI, stop there.  */
+         && !(stop_at_pdi && type == PDI)
          /* Stop when searched too far into an abnormally large
             paragraph full of weak or neutral characters.  */
          && pos - pos1 < MAX_STRONG_CHAR_SEARCH;
@@ -1440,6 +1462,7 @@ find_first_strong_char (ptrdiff_t pos, ptrdiff_t bytepos, ptrdiff_t end,
       pos += *nchars;
       bytepos += *ch_len;
     }
+  return type;
 }
 
 /* Determine the base direction, a.k.a. base embedding level, of the
@@ -1545,7 +1568,7 @@ bidi_paragraph_init (bidi_dir_t dir, struct bidi_it *bidi_it, bool no_default_p)
         type = find_first_strong_char (pos, bytepos, end, &disp_pos, &disp_prop,
                                        &bidi_it->string, bidi_it->w,
                                        string_p, bidi_it->frame_window_p,
-                                       &ch_len, &nchars);
+                                       &ch_len, &nchars, false);
         if (type == STRONG_R || type == STRONG_AL) /* P3 */
           bidi_it->paragraph_dir = R2L;
         else if (type == STRONG_L)
@@ -1619,7 +1642,7 @@ static int
 bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
 {
   int curchar;
-  bidi_type_t type;
+  bidi_type_t type, typ1;
   int current_level;
   int new_level;
   bidi_dir_t override;
@@ -1775,19 +1798,28 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
           type = WEAK_EN;
         break;
       case FSI: /* X5c */
-        bidi_it->type_after_w1 = type;
         end = string_p ? bidi_it->string.schars : ZV;
         disp_pos = bidi_it->disp_pos;
         disp_prop = bidi_it->disp_prop;
-        type = find_first_strong_char (bidi_it->charpos, bidi_it->bytepos, end,
+        nchars = bidi_it->nchars;
+        ch_len = bidi_it->ch_len;
+        typ1 = find_first_strong_char (bidi_it->charpos, bidi_it->bytepos, end,
                                        &disp_pos, &disp_prop, &bidi_it->string,
                                        bidi_it->w, string_p, bidi_it->frame_window_p,
-                                       &ch_len, &nchars);
-        if (type != STRONG_R && type != STRONG_AL)
-          goto fsi_as_lri;
+                                       &ch_len, &nchars, true);
+        if (typ1 != STRONG_R && typ1 != STRONG_AL)
+          {
+            type = LRI;
+            goto fsi_as_lri;
+          }
+        else
+          type == RLI;
         /* FALLTHROUGH */
       case RLI: /* X5a */
-        bidi_it->type_after_w1 = type;
+        if (override == NEUTRAL_DIR)
+          bidi_it->type_after_w1 = type;
+        else    /* Unicode 8.0 correction.  */
+          bidi_it->type_after_w1 = (override == L2R ? STRONG_L : STRONG_R);
         bidi_check_type (bidi_it->type_after_w1);
         if (current_level < BIDI_MAXDEPTH
             && bidi_it->invalid_levels == 0
@@ -1802,7 +1834,10 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
         break;
       case LRI: /* X5b */
     fsi_as_lri:
-        bidi_it->type_after_w1 = type;
+        if (override == NEUTRAL_DIR)
+          bidi_it->type_after_w1 = type;
+        else    /* Unicode 8.0 correction.  */
+          bidi_it->type_after_w1 = (override == L2R ? STRONG_L : STRONG_R);
         bidi_check_type (bidi_it->type_after_w1);
         if (current_level < BIDI_MAXDEPTH - 1
             && bidi_it->invalid_levels == 0
@@ -1817,7 +1852,10 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
         break;
       case PDI: /* X6a */
         if (bidi_it->invalid_isolates)
-          bidi_it->invalid_isolates--;
+          {
+            bidi_it->invalid_isolates--;
+            new_level = current_level;
+          }
         else if (bidi_it->isolate_level > 0)
           {
             bidi_it->invalid_levels = 0;
@@ -1825,9 +1863,16 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
               bidi_pop_embedding_level (bidi_it);
             eassert (bidi_it->stack_idx > 0);
             new_level = bidi_pop_embedding_level (bidi_it);
-            bidi_it->resolved_level = new_level;
             bidi_it->isolate_level--;
           }
+        bidi_it->resolved_level = new_level;
+        /* Unicode 8.0 correction.  */
+        if (bidi_it->level_stack[bidi_it->stack_idx].override == L2R)
+          bidi_it->type_after_w1 = STRONG_L;
+        else if (bidi_it->level_stack[bidi_it->stack_idx].override == R2L)
+          bidi_it->type_after_w1 = STRONG_R;
+        else
+          bidi_it->type_after_w1 = type;
         break;
       case PDF: /* X7 */
         bidi_it->type_after_w1 = type;