Improve the speedup of bidi display introduced in 2011-10-18T16:56:09Z!eliz@gnu.org for bug#9771.

 src/dispextern.h (struct bidi_it): New member next_en_type.
 src/bidi.c (bidi_line_init): Initialize the next_en_type member.
 (bidi_resolve_explicit_1): When next_en_pos is valid for the
 current character, check also for next_en_type being WEAK_EN.
 (bidi_resolve_weak): Don't enter the expensive loop if the current
 position is before next_en_pos.  Record the bidi type of the first
 non-ET, non-BN character we find, in addition to its position.
 (bidi_level_of_next_char): Invalidate next_en_type when
 next_en_pos is over-stepped.

3 files changed, 43 insertions, 15 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 36b205a120d..3f9b5beeab6 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,16 @@
+2011-10-20  Eli Zaretskii  <eliz@gnu.org>
+
+        * dispextern.h (struct bidi_it): New member next_en_type.
+
+        * bidi.c (bidi_line_init): Initialize the next_en_type member.
+        (bidi_resolve_explicit_1): When next_en_pos is valid for the
+        current character, check also for next_en_type being WEAK_EN.
+        (bidi_resolve_weak): Don't enter the expensive loop if the current
+        position is before next_en_pos.  Record the bidi type of the first
+        non-ET, non-BN character we find, in addition to its position.
+        (bidi_level_of_next_char): Invalidate next_en_type when
+        next_en_pos is over-stepped.
+
 2011-10-20  Paul Eggert  <eggert@cs.ucla.edu>
 
         Time zone name fixes for non-ASCII locales (Bug#641, Bug#9794)
diff --git a/src/bidi.c b/src/bidi.c
index 29e3c817318..d13baed63ed 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -849,6 +849,7 @@ bidi_line_init (struct bidi_it *bidi_it)
   /* Setting this to zero will force its recomputation the first time
      we need it for W5.  */
   bidi_it->next_en_pos = 0;
+  bidi_it->next_en_type = UNKNOWN_BT;
   bidi_it->next_for_ws.type = UNKNOWN_BT;
   bidi_set_sor_type (bidi_it,
                      (bidi_it->paragraph_dir == R2L ? 1 : 0),
@@ -1437,7 +1438,8 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
               }
           }
         else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
-                 || bidi_it->next_en_pos > bidi_it->charpos)
+                 || (bidi_it->next_en_pos > bidi_it->charpos
+                     && bidi_it->next_en_type == WEAK_EN))
           type = WEAK_EN;
         break;
       case LRE: /* X3 */
@@ -1473,7 +1475,8 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
               }
           }
         else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
-                 || bidi_it->next_en_pos > bidi_it->charpos)
+                 || (bidi_it->next_en_pos > bidi_it->charpos
+                     && bidi_it->next_en_type == WEAK_EN))
           type = WEAK_EN;
         break;
       case PDF: /* X7 */
@@ -1499,7 +1502,8 @@ bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
               }
           }
         else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
-                 || bidi_it->next_en_pos > bidi_it->charpos)
+                 || (bidi_it->next_en_pos > bidi_it->charpos
+                     && bidi_it->next_en_type == WEAK_EN))
           type = WEAK_EN;
         break;
       default:
@@ -1731,10 +1735,15 @@ bidi_resolve_weak (struct bidi_it *bidi_it)
       else if (type == WEAK_ET  /* W5: ET with EN before or after it */
                || type == WEAK_BN)      /* W5/Retaining */
         {
-          if (bidi_it->prev.type_after_w1 == WEAK_EN /* ET/BN w/EN before it */
-              || bidi_it->next_en_pos > bidi_it->charpos)
+          if (bidi_it->prev.type_after_w1 == WEAK_EN) /* ET/BN w/EN before it */
             type = WEAK_EN;
-          else if (bidi_it->next_en_pos >=0) /* W5: ET/BN with EN after it.  */
+          else if (bidi_it->next_en_pos > bidi_it->charpos
+                   && bidi_it->next_en_type != WEAK_BN)
+            {
+              if (bidi_it->next_en_type == WEAK_EN) /* ET/BN with EN after it */
+                type = WEAK_EN;
+            }
+          else if (bidi_it->next_en_pos >=0)
             {
               EMACS_INT en_pos = bidi_it->charpos + bidi_it->nchars;
               const unsigned char *s = (STRINGP (bidi_it->string.lstring)
@@ -1763,25 +1772,27 @@ bidi_resolve_weak (struct bidi_it *bidi_it)
                   en_pos = bidi_it->charpos;
                   bidi_copy_it (bidi_it, &saved_it);
                 }
+              /* Remember this position, to speed up processing of the
+                 next ETs.  */
+              bidi_it->next_en_pos = en_pos;
               if (type_of_next == WEAK_EN)
                 {
                   /* If the last strong character is AL, the EN we've
                      found will become AN when we get to it (W2). */
-                  if (bidi_it->last_strong.type_after_w1 != STRONG_AL)
-                    {
-                      type = WEAK_EN;
-                      /* Remember this EN position, to speed up processing
-                         of the next ETs.  */
-                      bidi_it->next_en_pos = en_pos;
-                    }
+                  if (bidi_it->last_strong.type_after_w1 == STRONG_AL)
+                    type_of_next = WEAK_AN;
                   else if (type == WEAK_BN)
                     type = NEUTRAL_ON; /* W6/Retaining */
+                  else
+                    type = WEAK_EN;
                 }
               else if (type_of_next == NEUTRAL_B)
                 /* Record the fact that there are no more ENs from
                    here to the end of paragraph, to avoid entering the
                    loop above ever again in this paragraph.  */
                 bidi_it->next_en_pos = -1;
+              /* Record the type of the character where we ended our search.  */
+              bidi_it->next_en_type = type_of_next;
             }
         }
     }
@@ -2053,7 +2064,10 @@ bidi_level_of_next_char (struct bidi_it *bidi_it)
         bidi_it->next_for_neutral.type = UNKNOWN_BT;
       if (bidi_it->next_en_pos >= 0
           && bidi_it->charpos >= bidi_it->next_en_pos)
-        bidi_it->next_en_pos = 0;
+        {
+          bidi_it->next_en_pos = 0;
+          bidi_it->next_en_type = UNKNOWN_BT;
+        }
       if (bidi_it->next_for_ws.type != UNKNOWN_BT
           && bidi_it->charpos >= bidi_it->next_for_ws.charpos)
         bidi_it->next_for_ws.type = UNKNOWN_BT;
diff --git a/src/dispextern.h b/src/dispextern.h
index 3c157371ef3..dd5f67d2d10 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1856,7 +1856,8 @@ struct bidi_it {
   struct bidi_saved_info next_for_neutral; /* surrounding characters for... */
   struct bidi_saved_info prev_for_neutral; /* ...resolving neutrals */
   struct bidi_saved_info next_for_ws; /* character after sequence of ws */
-  EMACS_INT next_en_pos;        /* position of next EN char for ET */
+  EMACS_INT next_en_pos;        /* pos. of next char for determining ET type */
+  bidi_type_t next_en_type;     /* type of char at next_en_pos */
   EMACS_INT ignore_bn_limit;    /* position until which to ignore BNs */
   bidi_dir_t sor;               /* direction of start-of-run in effect */
   int scan_dir;                 /* direction of text scan, 1: forw, -1: back */