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Speed up display of RTL text with many character compositions

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* src/bidi.c (bidi_level_start): New function.
* src/dispextern.h (bidi_level_start): Add prototype.
* src/xdisp.c (compute_stop_pos, set_iterator_to_next)
(get_visually_first_element, next_element_from_buffer): Call
'bidi_level_start' when looking for composed characters backwards,
to set limit of searching back, instead of looking all the way to
BOB.  (Bug#69385)
This commit is contained in:
Eli Zaretskii 2024-03-21 10:25:56 +02:00
parent b3f04eb684
commit fe24a8c3c0
3 changed files with 25 additions and 9 deletions
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13
src/bidi.c
View file

@ -754,6 +754,19 @@ bidi_cache_find_level_change (int level, int dir, bool before)
return -1;
}
/* Find the previous character position where LEVEL changes to a lower
one. Return -1 if not found (which really shouldn't happen if this
function is called on a backward scan). */
ptrdiff_t
bidi_level_start (int level)
{
ptrdiff_t slot = bidi_cache_find_level_change (level, -1, true);
if (slot >= 0)
return bidi_cache[slot].charpos;
return -1;
}
static void
bidi_cache_ensure_space (ptrdiff_t idx)
{

1
src/dispextern.h
View file

@ -3438,6 +3438,7 @@ extern void bidi_pop_it (struct bidi_it *);
extern void *bidi_shelve_cache (void);
extern void bidi_unshelve_cache (void *, bool);
extern ptrdiff_t bidi_find_first_overridden (struct bidi_it *);
extern ptrdiff_t bidi_level_start (int);
/* Defined in xdisp.c */

20
src/xdisp.c
View file

@ -4353,7 +4353,7 @@ compute_stop_pos (struct it *it)
an automatic composition, limit the search of composable
characters to that position. */
if (it->bidi_p && it->bidi_it.scan_dir < 0)
stoppos = -1;
stoppos = bidi_level_start (it->bidi_it.resolved_level) - 1;
else if (!STRINGP (it->string)
&& it->cmp_it.stop_pos <= IT_CHARPOS (*it)
&& cmp_limit_pos > 0)
@ -8712,9 +8712,8 @@ set_iterator_to_next (struct it *it, bool reseat_p)
ptrdiff_t stop = it->end_charpos;
if (it->bidi_it.scan_dir < 0)
/* Now we are scanning backward and don't know
where to stop. */
stop = -1;
/* Now we are scanning backward; figure out where to stop. */
stop = bidi_level_start (it->bidi_it.resolved_level) - 1;
composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
IT_BYTEPOS (*it), stop, Qnil, true);
}
@ -8745,7 +8744,7 @@ set_iterator_to_next (struct it *it, bool reseat_p)
re-compute the stop position for composition. */
ptrdiff_t stop = it->end_charpos;
if (it->bidi_it.scan_dir < 0)
stop = -1;
stop = bidi_level_start (it->bidi_it.resolved_level) - 1;
composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
IT_BYTEPOS (*it), stop, Qnil,
true);
@ -9190,7 +9189,9 @@ get_visually_first_element (struct it *it)
bytepos = IT_BYTEPOS (*it);
}
if (it->bidi_it.scan_dir < 0)
stop = -1;
stop = STRINGP (it->string)
? -1
: bidi_level_start (it->bidi_it.resolved_level) - 1;
composition_compute_stop_pos (&it->cmp_it, charpos, bytepos, stop,
it->string, true);
}
@ -9694,9 +9695,10 @@ next_element_from_buffer (struct it *it)
&& PT < it->end_charpos) ? PT : it->end_charpos;
}
else
stop = it->bidi_it.scan_dir < 0 ? -1 : it->end_charpos;
if (CHAR_COMPOSED_P (it, IT_CHARPOS (*it), IT_BYTEPOS (*it),
stop)
stop = it->bidi_it.scan_dir < 0
? bidi_level_start (it->bidi_it.resolved_level) - 1
: it->end_charpos;
if (CHAR_COMPOSED_P (it, IT_CHARPOS (*it), IT_BYTEPOS (*it), stop)
&& next_element_from_composition (it))
{
return true;