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Improve accuracy of cursor motion commands in long lines

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* src/xdisp.c (get_nearby_bol_pos): New function.
(get_small_narrowing_begv): Use it.  This makes cursor motion
commands much more accurate in the first 500K characters of each
long line.
This commit is contained in:
Gregory Heytings 2023-03-28 23:06:56 +00:00
parent 7e26a5c774
commit afc2c6c13c
1 changed files with 21 additions and 2 deletions
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23
src/xdisp.c
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@ -3608,11 +3608,30 @@ get_medium_narrowing_zv (struct window *w, ptrdiff_t pos)
return min ((pos / len + 1) * len, ZV);
}
static ptrdiff_t
get_nearby_bol_pos (ptrdiff_t pos)
{
ptrdiff_t start, pos_bytepos, cur, next, found, bol = 0;
start = pos - 500000 < BEGV ? BEGV : pos - 500000;
pos_bytepos = CHAR_TO_BYTE (pos);
for (cur = start; cur < pos; cur = next)
{
next = find_newline1 (cur, CHAR_TO_BYTE (cur), pos, pos_bytepos,
1, &found, NULL, false);
if (found)
bol = next;
else
break;
}
return bol;
}
ptrdiff_t
get_small_narrowing_begv (struct window *w, ptrdiff_t pos)
{
int len = get_narrowed_width (w);
return max ((pos / len - 1) * len, BEGV);
int bol_pos = get_nearby_bol_pos (pos);
return max (bol_pos + ((pos - bol_pos) / len - 1) * len, BEGV);
}
ptrdiff_t
@ -3653,7 +3672,7 @@ unwind_narrowed_begv (Lisp_Object point_min)
#define SET_WITH_NARROWED_BEGV(IT,DST,EXPR,BV) \
do { \
if (IT->medium_narrowing_begv) \
if (IT->medium_narrowing_begv) \
{ \
specpdl_ref count = SPECPDL_INDEX (); \
record_unwind_protect (unwind_narrowed_begv, Fpoint_min ()); \