8 files changed, 617 insertions, 47 deletions

diff --git a/src/buffer.c b/src/buffer.c
index a408b799ff4..e1f138d6f42 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -641,6 +641,13 @@ even if it is dead.  The return value is never nil.  */)
   bset_width_table (b, Qnil);
   b->prevent_redisplay_optimizations_p = 1;
 
+#ifdef HAVE_TREE_SITTER
+  b->ts_linecol_cache.pos = 1;
+  b->ts_linecol_cache.byte_pos = 1;
+  b->ts_linecol_cache.line = 1;
+  b->ts_linecol_cache.col = 0;
+#endif
+
   /* An ordinary buffer normally doesn't need markers
      to handle BEGV and ZV.  */
   bset_pt_marker (b, Qnil);
@@ -867,6 +874,13 @@ Interactively, CLONE and INHIBIT-BUFFER-HOOKS are nil.  */)
   b->bidi_paragraph_cache = 0;
   bset_width_table (b, Qnil);
 
+#ifdef HAVE_TREE_SITTER
+  b->ts_linecol_cache.pos = 1;
+  b->ts_linecol_cache.byte_pos = 1;
+  b->ts_linecol_cache.line = 1;
+  b->ts_linecol_cache.col = 0;
+#endif
+
   name = Fcopy_sequence (name);
   set_string_intervals (name, NULL);
   bset_name (b, name);
@@ -2618,6 +2632,11 @@ results, see Info node `(elisp)Swapping Text'.  */)
   bset_point_before_scroll (current_buffer, Qnil);
   bset_point_before_scroll (other_buffer, Qnil);
 
+#ifdef HAVE_TREE_SITTER
+  swapfield_ (ts_parser_list, Lisp_Object);
+  swapfield (ts_linecol_cache, struct ts_linecol);
+#endif
+
   modiff_incr (&current_buffer->text->modiff, 1);
   modiff_incr (&other_buffer->text->modiff, 1);
   modiff_incr (&current_buffer->text->chars_modiff, 1);
@@ -5019,8 +5038,6 @@ DEFUN ("overlay-tree", Foverlay_tree, Soverlay_tree, 0, 1, 0,
 }
 #endif
 
-
-
 /* Initialize the buffer routines.  */
 void
 syms_of_buffer (void)
diff --git a/src/buffer.h b/src/buffer.h
index 5c0a6ab3118..9479b141424 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -220,6 +220,23 @@ extern ptrdiff_t advance_to_char_boundary (ptrdiff_t byte_pos);
 
 /* Define the actual buffer data structures.  */
 
+/* This data structure stores the cache of a position and its line and
+   column number.  The column number is counted in bytes.  The line
+   number and column number don't consider narrowing.  */
+struct ts_linecol
+{
+  /* A position in the buffer.  */
+  ptrdiff_t pos;
+  /* The byte position of POS.  */
+  ptrdiff_t byte_pos;
+  /* The line number of this position.  */
+  ptrdiff_t line;
+  /* The column number (in bytes) of this position.  Unlike Emacs'
+     convention, this is 0-based (because tree-sitter column is
+     0-based).  Simply the byte offset from BOL (or BOB).  */
+  ptrdiff_t col;
+};
+
 /* This data structure describes the actual text contents of a buffer.
    It is shared between indirect buffers and their base buffer.  */
 
@@ -700,6 +717,19 @@ struct buffer
   /* The interval tree containing this buffer's overlays. */
   struct itree_tree *overlays;
 
+  /* Right now only tree-sitter makes use of this, so I don't want
+     non-tree-sitter build to pay for it.  If something else can make
+     use of this, we can remove the gate.  */
+#ifdef HAVE_TREE_SITTER
+  /* Cache of line and column number of a position.  The position cached
+     is usually near point.  Tree-sitter uses this cache to calculate
+     line and column of the beginning and end of buffer edits.  This
+     cache is refreshed in buffer edit functions, so it's always
+     up-to-date.  Usually, the newly calculated position and line/column
+     are saved to this field.  Initialized to position 1.  */
+  struct ts_linecol ts_linecol_cache;
+#endif
+
   /* Changes in the buffer are recorded here for undo, and t means
      don't record anything.  This information belongs to the base
      buffer of an indirect buffer.  But we can't store it in the
diff --git a/src/casefiddle.c b/src/casefiddle.c
index faeb16fb8f2..dba483460ce 100644
--- a/src/casefiddle.c
+++ b/src/casefiddle.c
@@ -543,6 +543,12 @@ casify_region (enum case_action flag, Lisp_Object b, Lisp_Object e)
 #ifdef HAVE_TREE_SITTER
   ptrdiff_t start_byte = CHAR_TO_BYTE (start);
   ptrdiff_t old_end_byte = CHAR_TO_BYTE (end);
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (start, start_byte,
+                              current_buffer->ts_linecol_cache);
+  struct ts_linecol old_end_linecol
+    = treesit_linecol_maybe (end, old_end_byte,
+                              current_buffer->ts_linecol_cache);
 #endif
 
   ptrdiff_t orig_end = end;
@@ -565,8 +571,11 @@ casify_region (enum case_action flag, Lisp_Object b, Lisp_Object e)
       update_compositions (start, end, CHECK_ALL);
     }
 #ifdef HAVE_TREE_SITTER
-      treesit_record_change (start_byte, old_end_byte,
-                             CHAR_TO_BYTE (orig_end + added));
+  ptrdiff_t new_end = orig_end + added;
+  ptrdiff_t new_end_byte = CHAR_TO_BYTE (new_end);
+
+  treesit_record_change (start_byte, old_end_byte, new_end_byte,
+                         start_linecol, old_end_linecol, new_end);
 #endif
 
   return orig_end + added;
diff --git a/src/editfns.c b/src/editfns.c
index f4e9a022fe2..5d5f4b30015 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -2234,6 +2234,19 @@ Both characters must have the same length of multi-byte form.  */)
     = !NILP (BVAR (current_buffer, enable_multibyte_characters));
   int fromc, toc;
 
+#ifdef HAVE_TREE_SITTER
+  ptrdiff_t start_char = fix_position (start);
+  ptrdiff_t old_end_char = fix_position (end);
+  ptrdiff_t start_byte = CHAR_TO_BYTE (start_char);
+  ptrdiff_t old_end_byte = CHAR_TO_BYTE (old_end_char);
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (start_char, start_byte,
+                             current_buffer->ts_linecol_cache);
+  struct ts_linecol old_end_linecol
+    = treesit_linecol_maybe (old_end_char, old_end_byte,
+                              current_buffer->ts_linecol_cache);
+#endif
+
  restart:
 
   validate_region (&start, &end);
@@ -2334,7 +2347,8 @@ Both characters must have the same length of multi-byte form.  */)
   if (changed > 0)
     {
 #ifdef HAVE_TREE_SITTER
-      treesit_record_change (changed, last_changed, last_changed);
+      treesit_record_change (start_byte, old_end_byte, old_end_byte,
+                             start_linecol, old_end_linecol, old_end_char);
 #endif
       signal_after_change (changed,
                            last_changed - changed, last_changed - changed);
@@ -2521,6 +2535,14 @@ It returns the number of characters changed.  */)
                 }
               else
                 {
+#ifdef HAVE_TREE_SITTER
+                  struct ts_linecol start_linecol
+                    = treesit_linecol_maybe (pos, pos_byte,
+                                             current_buffer->ts_linecol_cache);
+                  struct ts_linecol old_end_linecol
+                    = treesit_linecol_maybe (pos + 1, pos_byte + len,
+                                             start_linecol);
+#endif
                   record_change (pos, 1);
                   while (str_len-- > 0)
                     *p++ = *str++;
@@ -2528,12 +2550,13 @@ It returns the number of characters changed.  */)
                   update_compositions (pos, pos + 1, CHECK_BORDER);
 
 #ifdef HAVE_TREE_SITTER
-                  /* In the previous branch, replace_range() notifies
+                    /* In the previous branch, replace_range() notifies
                      changes to tree-sitter, but in this branch, we
                      modified buffer content manually, so we need to
                      notify tree-sitter manually.  */
                   treesit_record_change (pos_byte, pos_byte + len,
-                                         pos_byte + len);
+                                         pos_byte + len, start_linecol,
+                                         old_end_linecol, pos + 1);
 #endif
                 }
               characters_changed++;
@@ -4481,6 +4504,15 @@ ring.  */)
   start1_byte = CHAR_TO_BYTE (start1);
   end2_byte = CHAR_TO_BYTE (end2);
 
+#ifdef HAVE_TREE_SITTER
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (start1, start1_byte,
+                             current_buffer->ts_linecol_cache);
+  struct ts_linecol old_end_linecol
+    = treesit_linecol_maybe (end2, end2_byte,
+                              current_buffer->ts_linecol_cache);
+#endif
+
   /* Make sure the gap won't interfere, by moving it out of the text
      we will operate on.  */
   if (start1 < gap && gap < end2)
@@ -4620,10 +4652,8 @@ ring.  */)
     }
 
 #ifdef HAVE_TREE_SITTER
-  /* I don't think it's common to transpose two far-apart regions, so
-     amalgamating the edit into one should be fine.  This is what the
-     signal_after_change below does, too.  */
-  treesit_record_change (start1_byte, end2_byte, end2_byte);
+  treesit_record_change (start1_byte, end2_byte, end2_byte,
+                         start_linecol, old_end_linecol, end2);
 #endif
 
   signal_after_change (start1, end2 - start1, end2 - start1);
diff --git a/src/insdel.c b/src/insdel.c
index 9b770725971..dd5be1d9ca7 100644
--- a/src/insdel.c
+++ b/src/insdel.c
@@ -891,6 +891,11 @@ insert_1_both (const char *string,
   if (NILP (BVAR (current_buffer, enable_multibyte_characters)))
     nchars = nbytes;
 
+#ifdef HAVE_TREE_SITTER
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (PT, PT_BYTE, current_buffer->ts_linecol_cache);
+#endif
+
   if (prepare)
     /* Do this before moving and increasing the gap,
        because the before-change hooks might move the gap
@@ -945,7 +950,9 @@ insert_1_both (const char *string,
 #ifdef HAVE_TREE_SITTER
   eassert (nbytes >= 0);
   eassert (PT_BYTE >= 0);
-  treesit_record_change (PT_BYTE, PT_BYTE, PT_BYTE + nbytes);
+
+  treesit_record_change (PT_BYTE, PT_BYTE, PT_BYTE + nbytes,
+                         start_linecol, start_linecol, PT + nchars);
 #endif
 
   adjust_point (nchars, nbytes);
@@ -1017,6 +1024,11 @@ insert_from_string_1 (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
       = count_size_as_multibyte (SDATA (string) + pos_byte,
                                  nbytes);
 
+#ifdef HAVE_TREE_SITTER
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (PT, PT_BYTE, current_buffer->ts_linecol_cache);
+#endif
+
   /* Do this before moving and increasing the gap,
      because the before-change hooks might move the gap
      or make it smaller.  */
@@ -1081,7 +1093,9 @@ insert_from_string_1 (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
 #ifdef HAVE_TREE_SITTER
   eassert (nbytes >= 0);
   eassert (PT_BYTE >= 0);
-  treesit_record_change (PT_BYTE, PT_BYTE, PT_BYTE + nbytes);
+
+  treesit_record_change (PT_BYTE, PT_BYTE, PT_BYTE + nbytes,
+                         start_linecol, start_linecol, PT + nchars);
 #endif
 
   adjust_point (nchars, outgoing_nbytes);
@@ -1094,7 +1108,8 @@ insert_from_string_1 (Lisp_Object string, ptrdiff_t pos, ptrdiff_t pos_byte,
    GPT_ADDR (if not text_at_gap_tail).
    Contrary to insert_from_gap, this does not invalidate any cache,
    nor update any markers, nor record any buffer modification information
-   of any sort, with the single exception of notifying tree-sitter.  */
+   of any sort, with the single exception of notifying tree-sitter and
+   updating tree-sitter linecol cache.  */
 void
 insert_from_gap_1 (ptrdiff_t nchars, ptrdiff_t nbytes, bool text_at_gap_tail)
 {
@@ -1103,6 +1118,8 @@ insert_from_gap_1 (ptrdiff_t nchars, ptrdiff_t nbytes, bool text_at_gap_tail)
 
 #ifdef HAVE_TREE_SITTER
   ptrdiff_t ins_bytepos = GPT_BYTE;
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (GPT, GPT_BYTE, current_buffer->ts_linecol_cache);
 #endif
 
   GAP_SIZE -= nbytes;
@@ -1123,7 +1140,9 @@ insert_from_gap_1 (ptrdiff_t nchars, ptrdiff_t nbytes, bool text_at_gap_tail)
 #ifdef HAVE_TREE_SITTER
   eassert (nbytes >= 0);
   eassert (ins_bytepos >= 0);
-  treesit_record_change (ins_bytepos, ins_bytepos, ins_bytepos + nbytes);
+
+  treesit_record_change (ins_bytepos, ins_bytepos, ins_bytepos + nbytes,
+                         start_linecol, start_linecol, ins_bytepos + nbytes);
 #endif
 }
 
@@ -1186,6 +1205,8 @@ insert_from_buffer (struct buffer *buf,
 
 #ifdef HAVE_TREE_SITTER
   ptrdiff_t obyte = PT_BYTE;
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (opoint, obyte, current_buffer->ts_linecol_cache);
 #endif
 
   insert_from_buffer_1 (buf, charpos, nchars, inherit);
@@ -1196,7 +1217,9 @@ insert_from_buffer (struct buffer *buf,
   eassert (PT_BYTE >= BEG_BYTE);
   eassert (obyte >= BEG_BYTE);
   eassert (PT_BYTE >= obyte);
-  treesit_record_change (obyte, obyte, PT_BYTE);
+
+  treesit_record_change (obyte, obyte, PT_BYTE,
+                         start_linecol, start_linecol, PT);
 #endif
 }
 
@@ -1481,6 +1504,14 @@ replace_range (ptrdiff_t from, ptrdiff_t to, Lisp_Object new,
   if (nbytes_del <= 0 && inschars == 0)
     return;
 
+#ifdef HAVE_TREE_SITTER
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (from, from_byte, current_buffer->ts_linecol_cache);
+  struct ts_linecol old_end_linecol
+    = treesit_linecol_maybe (to, to_byte, current_buffer->ts_linecol_cache);
+#endif
+
+
   ptrdiff_t insbeg_bytes, insend_bytes;
   ptrdiff_t insbytes;
   unsigned char *insbeg_ptr;
@@ -1623,7 +1654,9 @@ replace_range (ptrdiff_t from, ptrdiff_t to, Lisp_Object new,
   eassert (to_byte >= from_byte);
   eassert (outgoing_insbytes >= 0);
   eassert (from_byte >= 0);
-  treesit_record_change (from_byte, to_byte, from_byte + outgoing_insbytes);
+
+  treesit_record_change (from_byte, to_byte, from_byte + outgoing_insbytes,
+                         start_linecol, old_end_linecol, from + inschars);
 #endif
 
   /* Relocate point as if it were a marker.  */
@@ -1948,6 +1981,13 @@ del_range_2 (ptrdiff_t from, ptrdiff_t from_byte,
   nchars_del = to - from;
   nbytes_del = to_byte - from_byte;
 
+#ifdef HAVE_TREE_SITTER
+  struct ts_linecol start_linecol
+    = treesit_linecol_maybe (from, from_byte, current_buffer->ts_linecol_cache);
+  struct ts_linecol old_end_linecol
+    = treesit_linecol_maybe (to, to_byte, current_buffer->ts_linecol_cache);
+#endif
+
   /* Make sure the gap is somewhere in or next to what we are deleting.  */
   if (from > GPT)
     gap_right (from, from_byte);
@@ -2007,7 +2047,8 @@ del_range_2 (ptrdiff_t from, ptrdiff_t from_byte,
 #ifdef HAVE_TREE_SITTER
   eassert (from_byte <= to_byte);
   eassert (from_byte >= 0);
-  treesit_record_change (from_byte, to_byte, from_byte);
+  treesit_record_change (from_byte, to_byte, from_byte,
+                         start_linecol, old_end_linecol, from);
 #endif
 
   return deletion;
diff --git a/src/treesit.c b/src/treesit.c
index b0979397d35..583a01b7f38 100644
--- a/src/treesit.c
+++ b/src/treesit.c
@@ -864,6 +864,176 @@ loaded or the file name couldn't be determined, return nil.  */)
 }
 
 
+/*** Linecol functions */
+
+#define TREE_SITTER_DEBUG_LINECOL true
+
+static void
+treesit_print_linecol (struct ts_linecol linecol)
+{
+  printf ("{ line=%ld col=%ld pos=%ld byte_pos=%ld }\n", linecol.line, linecol.col, linecol.pos, linecol.byte_pos);
+}
+
+static void
+treesit_validate_linecol (const char *name, struct ts_linecol linecol)
+{
+  eassert (linecol.pos <= Z);
+
+  if (linecol.pos > Z)
+    {
+      printf ("OUT OF RANGE\n");
+      treesit_print_linecol (linecol);
+      printf ("Z: %ld\n", Z);
+    }
+
+  ptrdiff_t true_line_count = count_lines (BEG, linecol.byte_pos) + 1;
+  eassert (true_line_count == linecol.line);
+
+  if (true_line_count != linecol.line)
+    {
+      printf ("MISMATCH\n");
+      printf ("%s: ", name);
+      treesit_print_linecol (linecol);
+      printf ("true: %ld\n", true_line_count);
+    }
+}
+
+/* Calculate and return the line and column number of BYTE_POS by
+   scanning newlines from CACHE.  CACHE must be valid.  */
+static struct ts_linecol
+treesit_linecol_of_pos (ptrdiff_t target_pos, ptrdiff_t target_byte_pos,
+                        struct ts_linecol cache)
+{
+  eassert (target_pos == target_byte_pos);
+
+  if (TREE_SITTER_DEBUG_LINECOL)
+    {
+      /* eassert (true_line_count == cache.line); */
+      treesit_validate_linecol ("cache", cache);
+    }
+
+  /* When we finished searching for newlines between CACHE and
+     TARGET_POS, BYTE_POS_2 is at TARGET_POS, and BYTE_POS_1 is at the
+     previous newline.  If TARGET_POS happends to be on a newline,
+     BYTE_POS_1 will be on that position.  BYTE_POS_1 is used for
+     calculating the column.  (If CACHE and TARGET_POS are in the same
+     line, BYTE_POS_1 is unset and we don't use it.)  */
+  ptrdiff_t byte_pos_1 = 0;
+  ptrdiff_t pos_2 = 0;
+  ptrdiff_t byte_pos_2 = 0;
+  /* Number of lines between CACHE and TARGET_POS.  */
+  ptrdiff_t line_delta = 0;
+
+  if (target_byte_pos == cache.byte_pos)
+    return cache;
+
+  /* Search forward. */
+  if (cache.byte_pos < target_byte_pos)
+    {
+      pos_2 = cache.pos;
+      byte_pos_2 = cache.byte_pos;
+      while (byte_pos_2 < target_byte_pos)
+        {
+          ptrdiff_t counted = 0;
+          pos_2 = find_newline (pos_2, byte_pos_2, target_pos, target_byte_pos,
+                                1, &counted, &byte_pos_2, false);
+
+          if (counted > 0) byte_pos_1 = byte_pos_2;
+          line_delta += counted;
+          /* printf ("byte_pos_2=%ld counted=%ld line_delta=%ld\n", byte_pos_2, counted, line_delta); */
+        }
+      eassert (byte_pos_2 == target_byte_pos);
+      /* At this point, byte_pos_2 is at target_pos, and byte_pos_1 is
+         at the previous newline if we went across any.  */
+
+      struct ts_linecol target_linecol;
+      target_linecol.pos = target_pos;
+      target_linecol.byte_pos = target_byte_pos;
+      target_linecol.line = cache.line + line_delta;
+      /* If we moved across any newline, use the previous newline to
+         calculate the column; if we stayed at the same line, use the
+         cached column to calculate the new column.  */
+      target_linecol.col = line_delta > 0
+        ? target_byte_pos - byte_pos_1
+        : target_byte_pos - cache.byte_pos + cache.col;
+
+      if (TREE_SITTER_DEBUG_LINECOL)
+        {
+          /* eassert (true_line_count == target_linecol.line); */
+          treesit_validate_linecol ("target", target_linecol);
+        }
+
+      return target_linecol;
+    }
+
+  /* Search backward. */
+  printf ("BACK\n");
+  pos_2 = cache.pos + 1;
+  /* The "+1" Cancels out with the "-1" in the first iteration. */
+  byte_pos_2 = cache.byte_pos + 1;
+  while (byte_pos_2 > target_byte_pos)
+    {
+      ptrdiff_t counted = 0;
+      /* pos_2 - 1 won't underflow because of the loop condition.  */
+      pos_2 = find_newline (pos_2 - 1, byte_pos_2 - 1,
+                            target_pos, target_byte_pos,
+                            -1, &counted, &byte_pos_2, false);
+      line_delta += counted;
+    }
+  eassert (byte_pos_2 == target_byte_pos);
+  /* At this point, pos_2 is at target_pos.  */
+
+  struct ts_linecol target_linecol;
+  target_linecol.pos = target_pos;
+  target_linecol.byte_pos = target_byte_pos;
+  target_linecol.line = cache.line + line_delta;
+  eassert (cache.line + line_delta > 0);
+
+  /* Calculate the column.  */
+  if (line_delta == 0)
+    {
+      target_linecol.col = cache.col - (cache.byte_pos - target_byte_pos);
+    }
+  else
+    {
+      /* We need to find the previous newline in order to calculate the
+         column.  Use POS_2 instead of POS_2 - 1, this way, if POS_2 is
+         at BOL, we stay in the same place.  */
+      pos_2 = find_newline (pos_2, byte_pos_2, BEG, BEG_BYTE, -1,
+                            NULL, &byte_pos_2, false);
+      target_linecol.col = target_byte_pos - byte_pos_2;
+    }
+
+  if (TREE_SITTER_DEBUG_LINECOL)
+    {
+      treesit_validate_linecol ("target", target_linecol);
+    }
+
+  return target_linecol;
+}
+
+/* Return a TSPoint given POS and VISIBLE_BEG.  VISIBLE_BEG must be
+   before POS.  */
+static TSPoint
+treesit_make_ts_point (struct ts_linecol visible_beg,
+                       struct ts_linecol pos)
+{
+  TSPoint point;
+  if (visible_beg.line == pos.line)
+    {
+      point.row = 0;
+      point.column = pos.col - visible_beg.col;
+      eassert (point.column >= 0);
+    }
+  else
+    {
+      point.row = pos.line - visible_beg.line;
+      eassert (point.row > 0);
+      point.column = pos.col;
+    }
+  return point;
+}
+
 /*** Parsing functions  */
 
 static void
@@ -879,28 +1049,34 @@ treesit_check_parser (Lisp_Object obj)
    larger than UINT32_MAX.  */
 static inline void
 treesit_tree_edit_1 (TSTree *tree, ptrdiff_t start_byte,
-                     ptrdiff_t old_end_byte, ptrdiff_t new_end_byte)
+                     ptrdiff_t old_end_byte, ptrdiff_t new_end_byte,
+                     TSPoint start_point, TSPoint old_end_point,
+                     TSPoint new_end_point)
 {
   eassert (start_byte >= 0);
   eassert (start_byte <= old_end_byte);
   eassert (start_byte <= new_end_byte);
-  TSPoint dummy_point = {0, 0};
   eassert (start_byte <= UINT32_MAX);
   eassert (old_end_byte <= UINT32_MAX);
   eassert (new_end_byte <= UINT32_MAX);
   TSInputEdit edit = {(uint32_t) start_byte,
                       (uint32_t) old_end_byte,
                       (uint32_t) new_end_byte,
-                      dummy_point, dummy_point, dummy_point};
+                      start_point, old_end_point, new_end_point};
   ts_tree_edit (tree, &edit);
 }
 
-/* Update each parser's tree after the user made an edit.  This
-   function does not parse the buffer and only updates the tree, so it
-   should be very fast.  */
-void
-treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
-                       ptrdiff_t new_end_byte)
+/* Update each parser's tree after the user made an edit.  This function
+   does not parse the buffer and only updates the tree, so it should be
+   very fast.  If the caller knows there's no parser in the current
+   buffer, they can pass empty linecol for
+   START/OLD_END/NEW_END_linecol.  */
+static void
+treesit_record_change_1 (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
+                         ptrdiff_t new_end_byte,
+                         struct ts_linecol start_linecol,
+                         struct ts_linecol old_end_linecol,
+                         struct ts_linecol new_end_linecol)
 {
   struct buffer *base_buffer = current_buffer;
   if (current_buffer->base_buffer)
@@ -920,12 +1096,15 @@ treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
         {
           eassert (start_byte <= old_end_byte);
           eassert (start_byte <= new_end_byte);
-          /* Think the recorded change as a delete followed by an
-             insert, and think of them as moving unchanged text back
-             and forth.  After all, the whole point of updating the
-             tree is to update the position of unchanged text.  */
-          ptrdiff_t visible_beg = XTS_PARSER (lisp_parser)->visible_beg;
-          ptrdiff_t visible_end = XTS_PARSER (lisp_parser)->visible_end;
+          /* Before sending the edit to tree-sitter, we need to first
+             clip the beg/end to visible_beg and visible_end of the
+             parser.  A tip for understanding the code below: think the
+             recorded change as a delete followed by an insert, and
+             think of them as moving unchanged text back and forth.
+             After all, the whole point of updating the tree is to
+             update the position of unchanged text.  */
+          const ptrdiff_t visible_beg = XTS_PARSER (lisp_parser)->visible_beg;
+          const ptrdiff_t visible_end = XTS_PARSER (lisp_parser)->visible_end;
           eassert (visible_beg >= 0);
           eassert (visible_beg <= visible_end);
 
@@ -949,9 +1128,9 @@ treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
           eassert (start_offset <= old_end_offset);
           eassert (start_offset <= new_end_offset);
 
-          treesit_tree_edit_1 (tree, start_offset, old_end_offset,
-                               new_end_offset);
-          XTS_PARSER (lisp_parser)->need_reparse = true;
+          /* We have the correct offset for start/end now, but don't
+             update the tree yet, because we still need to calculate the
+             TSPoint, which needs the updated visible_beg linecol.  */
 
           /* VISIBLE_BEG/END records tree-sitter's range of view in
              the buffer.  We need to adjust them when tree-sitter's
@@ -966,19 +1145,99 @@ treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
             visi_beg_delta = (old_end_byte < visible_beg
                               ? new_end_byte - old_end_byte : 0);
 
-          XTS_PARSER (lisp_parser)->visible_beg = visible_beg + visi_beg_delta;
-          XTS_PARSER (lisp_parser)->visible_end = (visible_end
-                                                   + visi_beg_delta
-                                                   + (new_end_offset
-                                                      - old_end_offset));
+          ptrdiff_t old_visi_beg = visible_beg;
+          struct ts_linecol old_visi_beg_linecol
+            = XTS_PARSER (lisp_parser)->visi_beg_linecol;
+          /* struct ts_linecol old_visi_end_linecol */
+          /*   = XTS_PARSER (lisp_parser)->visi_end_linecol; */
+
+          const ptrdiff_t new_visible_beg = visible_beg + visi_beg_delta;
+          const ptrdiff_t new_visible_end
+            = (visible_end + visi_beg_delta
+               + (new_end_offset - old_end_offset));
+
+          XTS_PARSER (lisp_parser)->visible_beg = new_visible_beg;
+          XTS_PARSER (lisp_parser)->visible_end = new_visible_end;
+          XTS_PARSER (lisp_parser)->visi_beg_linecol
+            = treesit_linecol_of_pos (BYTE_TO_CHAR (new_visible_beg),
+                                      new_visible_beg,
+                                      old_visi_beg <= start_byte
+                                        ? old_visi_beg_linecol
+                                        : start_linecol);
+          /* FIXME: computing visi_end_linecol from new_end_linecol
+             could be expensive, we need a more efficient way to compute
+             it.  */
+          XTS_PARSER (lisp_parser)->visi_end_linecol
+            = treesit_linecol_of_pos (BYTE_TO_CHAR (new_visible_end),
+                                      new_visible_end,
+                                      new_end_linecol);
 
           eassert (XTS_PARSER (lisp_parser)->visible_beg >= 0);
           eassert (XTS_PARSER (lisp_parser)->visible_beg
-                   <= XTS_PARSER (lisp_parser)->visible_end);
+                   <= XTS_PARSER (lisp_parser)->visible_end);
+
+          /* Now, calculate TSPoints and finally update the tree.  */
+          struct ts_linecol new_begv_linecol
+            = XTS_PARSER (lisp_parser)->visi_beg_linecol;
+          TSPoint old_end_point = treesit_make_ts_point (old_visi_beg_linecol,
+                                                         old_end_linecol);
+          TSPoint start_point = treesit_make_ts_point (new_begv_linecol,
+                                                       start_linecol);
+          TSPoint new_end_point = treesit_make_ts_point (new_begv_linecol,
+                                                         new_end_linecol);
+
+          treesit_tree_edit_1 (tree, start_offset, old_end_offset,
+                               new_end_offset, start_point, old_end_point,
+                               new_end_point);
+          XTS_PARSER (lisp_parser)->need_reparse = true;
         }
     }
 }
 
+/* Return the linecol of POS, calculated from CACHE.  But if there's no
+   parser in the current buffer, skip calculation and return an empty
+   linecol instead.  */
+struct ts_linecol
+treesit_linecol_maybe (ptrdiff_t pos, ptrdiff_t pos_byte,
+                       struct ts_linecol cache)
+{
+  if (NILP (BVAR (current_buffer, ts_parser_list)))
+    return TREESIT_EMPTY_LINECOL;
+
+  return treesit_linecol_of_pos (pos, pos_byte, cache);
+}
+
+/* Update each parser's tree after the user made an edit.  This function
+   does not parse the buffer and only updates the tree, so it should be
+   very fast.
+
+   This is a wrapper over treesit_record_change that does a bit more
+   boilerplate work: it (optionally) calculates linecol for new_end,
+   pass all the positions into treesit_record_change_1 which does the
+   real work, and finally (optionally) sets buffer's linecol cache to
+   new_end's linecol.
+
+   If NEW_END is next to NEW_END_BYTE in the arglist, caller might
+   accidentally swap them, so I placed NEW_END at the end of the
+   arglist.  */
+void
+treesit_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
+                       ptrdiff_t new_end_byte,
+                       struct ts_linecol start_linecol,
+                       struct ts_linecol old_end_linecol,
+                       ptrdiff_t new_end)
+{
+  struct ts_linecol new_end_linecol
+    = treesit_linecol_maybe (new_end, new_end_byte, start_linecol);
+
+  treesit_record_change_1 (start_byte, old_end_byte, new_end_byte,
+                           start_linecol, old_end_linecol, new_end_linecol);
+
+  treesit_print_linecol (new_end_linecol);
+  if (new_end_linecol.pos != 0)
+    current_buffer->ts_linecol_cache = new_end_linecol;
+}
+
 static TSRange *treesit_make_ts_ranges (Lisp_Object, Lisp_Object,
                                         uint32_t *);
 
@@ -1046,6 +1305,7 @@ treesit_sync_visible_region (Lisp_Object parser)
 
   ptrdiff_t visible_beg = XTS_PARSER (parser)->visible_beg;
   ptrdiff_t visible_end = XTS_PARSER (parser)->visible_end;
+
   eassert (0 <= visible_beg);
   eassert (visible_beg <= visible_end);
 
@@ -1066,39 +1326,72 @@ treesit_sync_visible_region (Lisp_Object parser)
      from ________|xxxx|__
      to   |xxxx|__________ */
 
+  struct ts_linecol buffer_linecol_cache = buffer->ts_linecol_cache;
+  struct ts_linecol visi_beg_linecol = XTS_PARSER (parser)->visi_beg_linecol;
+  struct ts_linecol visi_end_linecol = XTS_PARSER (parser)->visi_end_linecol;
+  struct ts_linecol buffer_begv_linecol
+    = treesit_linecol_of_pos (BUF_BEGV (buffer), BUF_BEGV_BYTE (buffer),
+                              visi_beg_linecol);
+  struct ts_linecol buffer_zv_linecol
+    = treesit_linecol_of_pos (BUF_ZV (buffer), BUF_ZV_BYTE (buffer),
+                              buffer_linecol_cache);
+  eassert (visi_beg_linecol.byte_pos == visible_beg);
+
   /* 1. Make sure visible_beg <= BUF_BEGV_BYTE.  */
   if (visible_beg > BUF_BEGV_BYTE (buffer))
     {
+      TSPoint new_end = treesit_make_ts_point (buffer_begv_linecol,
+                                               visi_beg_linecol);
       /* Tree-sitter sees: insert at the beginning.  */
-      treesit_tree_edit_1 (tree, 0, 0, visible_beg - BUF_BEGV_BYTE (buffer));
+      treesit_tree_edit_1 (tree, 0, 0, visible_beg - BUF_BEGV_BYTE (buffer),
+                           TREESIT_TS_POINT_1_0, TREESIT_TS_POINT_1_0,
+                           new_end);
       visible_beg = BUF_BEGV_BYTE (buffer);
+      visi_beg_linecol = buffer_begv_linecol;
       eassert (visible_beg <= visible_end);
     }
   /* 2. Make sure visible_end = BUF_ZV_BYTE.  */
   if (visible_end < BUF_ZV_BYTE (buffer))
     {
+      TSPoint start = treesit_make_ts_point (visi_beg_linecol,
+                                             visi_end_linecol);
+      TSPoint new_end = treesit_make_ts_point (visi_beg_linecol,
+                                               buffer_zv_linecol);
       /* Tree-sitter sees: insert at the end.  */
       treesit_tree_edit_1 (tree, visible_end - visible_beg,
                            visible_end - visible_beg,
-                           BUF_ZV_BYTE (buffer) - visible_beg);
+                           BUF_ZV_BYTE (buffer) - visible_beg,
+                           start, start, new_end);
       visible_end = BUF_ZV_BYTE (buffer);
+      visi_end_linecol = buffer_zv_linecol;
       eassert (visible_beg <= visible_end);
     }
   else if (visible_end > BUF_ZV_BYTE (buffer))
     {
+      TSPoint start = treesit_make_ts_point (visi_beg_linecol,
+                                             buffer_zv_linecol);
+      TSPoint old_end = treesit_make_ts_point (visi_beg_linecol,
+                                               visi_end_linecol);
       /* Tree-sitter sees: delete at the end.  */
       treesit_tree_edit_1 (tree, BUF_ZV_BYTE (buffer) - visible_beg,
                            visible_end - visible_beg,
-                           BUF_ZV_BYTE (buffer) - visible_beg);
+                           BUF_ZV_BYTE (buffer) - visible_beg,
+                           start, old_end, start);
       visible_end = BUF_ZV_BYTE (buffer);
+      visi_end_linecol = buffer_zv_linecol;
       eassert (visible_beg <= visible_end);
     }
   /* 3. Make sure visible_beg = BUF_BEGV_BYTE.  */
   if (visible_beg < BUF_BEGV_BYTE (buffer))
     {
+      TSPoint old_end = treesit_make_ts_point (visi_beg_linecol,
+                                               buffer_begv_linecol);
       /* Tree-sitter sees: delete at the beginning.  */
-      treesit_tree_edit_1 (tree, 0, BUF_BEGV_BYTE (buffer) - visible_beg, 0);
+      treesit_tree_edit_1 (tree, 0, BUF_BEGV_BYTE (buffer) - visible_beg, 0,
+                           TREESIT_TS_POINT_1_0, old_end,
+                           TREESIT_TS_POINT_1_0);
       visible_beg = BUF_BEGV_BYTE (buffer);
+      visi_beg_linecol = buffer_begv_linecol;
       eassert (visible_beg <= visible_end);
     }
   eassert (0 <= visible_beg);
@@ -1108,6 +1401,8 @@ treesit_sync_visible_region (Lisp_Object parser)
 
   XTS_PARSER (parser)->visible_beg = visible_beg;
   XTS_PARSER (parser)->visible_end = visible_end;
+  XTS_PARSER (parser)->visi_beg_linecol = visi_beg_linecol;
+  XTS_PARSER (parser)->visi_end_linecol = visi_end_linecol;
 
   /* Fix ranges so that the ranges stays with in visible_end.  Here we
      try to do minimal work so that the ranges is minimally correct and
@@ -1381,6 +1676,19 @@ make_treesit_parser (Lisp_Object buffer, TSParser *parser,
   lisp_parser->need_to_gc_buffer = false;
   lisp_parser->within_reparse = false;
   eassert (lisp_parser->visible_beg <= lisp_parser->visible_end);
+
+  struct buffer *old_buf = current_buffer;
+  set_buffer_internal (XBUFFER (buffer));
+
+  /* treesit_linecol_of_pos doesn't signal, so no need to
+     unwind-protect.  */
+  lisp_parser->visi_beg_linecol = treesit_linecol_of_pos (BEGV, BEGV_BYTE,
+                                                          TREESIT_BOB_LINECOL);
+  lisp_parser->visi_end_linecol
+    = treesit_linecol_of_pos (ZV, ZV_BYTE, lisp_parser->visi_beg_linecol);
+
+  set_buffer_internal (old_buf);
+
   return make_lisp_ptr (lisp_parser, Lisp_Vectorlike);
 }
 
@@ -4376,6 +4684,66 @@ nodes in the subtree, including NODE.  */)
     }
 }
 
+DEFUN ("treesit--linecol-at", Ftreesit__linecol_at,
+       Streesit__linecol_at, 1, 1, 0,
+       doc: /* Test buffer-local linecol cache.
+
+Calculate the line and column at POS using the buffer-local cache,
+return the line and column in the form of
+
+  (LINE . COL)
+
+This is used for testing and debugging only.  */)
+  (Lisp_Object pos)
+{
+  CHECK_NUMBER (pos);
+  struct ts_linecol pos_linecol
+    = treesit_linecol_of_pos (XFIXNUM (pos), CHAR_TO_BYTE (XFIXNUM (pos)),
+                              current_buffer->ts_linecol_cache);
+  return Fcons (make_fixnum (pos_linecol.line), make_fixnum (pos_linecol.col));
+}
+
+DEFUN ("treesit--linecol-cache-set", Ftreesit__linecol_cache_set,
+       Streesit__linecol_cache_set, 4, 4, 0,
+       doc: /* Set the linecol cache for the current buffer.
+
+This is used for testing and debugging only.  */)
+  (Lisp_Object line, Lisp_Object col, Lisp_Object pos, Lisp_Object bytepos)
+{
+  CHECK_FIXNUM (line);
+  CHECK_FIXNUM (col);
+  CHECK_FIXNUM (pos);
+  CHECK_FIXNUM (bytepos);
+
+  current_buffer->ts_linecol_cache.line = XFIXNUM (line);
+  current_buffer->ts_linecol_cache.col = XFIXNUM (col);
+  current_buffer->ts_linecol_cache.pos = XFIXNUM (pos);
+  current_buffer->ts_linecol_cache.byte_pos = XFIXNUM (bytepos);
+
+  return Qnil;
+}
+
+DEFUN ("treesit--linecol-cache", Ftreesit__linecol_cache,
+       Streesit__linecol_cache, 0, 0, 0,
+       doc: /* Return the buffer-local linecol cache for debugging.
+
+Return a plist (:line LINE :col COL :pos POS :bytepos BYTEPOS).  This is
+used for testing and debugging only.  */)
+  (void)
+{
+  struct ts_linecol cache = current_buffer->ts_linecol_cache;
+
+  Lisp_Object plist =  (list4 (QCpos, make_fixnum (cache.pos),
+                               QCbytepos, make_fixnum (cache.byte_pos)));
+  plist = Fcons (make_fixnum (cache.col), plist);
+  plist = Fcons (QCcol, plist);
+  plist = Fcons (make_fixnum (cache.line), plist);
+  plist = Fcons (QCline, plist);
+
+  return plist;
+}
+
+
 #endif  /* HAVE_TREE_SITTER */
 
 DEFUN ("treesit-available-p", Ftreesit_available_p,
@@ -4418,6 +4786,11 @@ syms_of_treesit (void)
   DEFSYM (QCequal, ":equal");
   DEFSYM (QCmatch, ":match");
   DEFSYM (QCpred, ":pred");
+  DEFSYM (QCline, ":line");
+  DEFSYM (QCcol, ":col");
+  DEFSYM (QCpos, ":pos");
+  DEFSYM (QCbytepos, ":bytepos");
+
 
   DEFSYM (Qnot_found, "not-found");
   DEFSYM (Qsymbol_error, "symbol-error");
@@ -4649,6 +5022,10 @@ applies to LANGUAGE-A will be redirected to LANGUAGE-B instead.  */);
   defsubr (&Streesit_induce_sparse_tree);
   defsubr (&Streesit_node_match_p);
   defsubr (&Streesit_subtree_stat);
+
+  defsubr (&Streesit__linecol_at);
+  defsubr (&Streesit__linecol_cache);
+  defsubr (&Streesit__linecol_cache_set);
 #endif /* HAVE_TREE_SITTER */
   defsubr (&Streesit_available_p);
 #ifdef WINDOWSNT
diff --git a/src/treesit.h b/src/treesit.h
index 0d4635f4253..b6a3f3a652c 100644
--- a/src/treesit.h
+++ b/src/treesit.h
@@ -26,6 +26,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <tree_sitter/api.h>
 #include "lisp.h"
+#include "buffer.h"
 
 INLINE_HEADER_BEGIN
 
@@ -97,6 +98,14 @@ struct Lisp_TS_Parser
      (ref:visible-beg-null) in treesit.c for more explanation.  */
   ptrdiff_t visible_beg;
   ptrdiff_t visible_end;
+  /* Caches the line and column number of VISIBLE_BEG.  It's always
+     valid and matches VISIBLE_BEG (because it's updated at each buffer
+     edit).  (It has to be, because in treesit_record_change, we need to
+     calculate the line/col offset of old_end_linecol, the exact reason
+     why is left as an exercise to the reader.)  */
+  struct ts_linecol visi_beg_linecol;
+  /* Similar to VISI_BEG_LINECOL but caches VISIBLE_END.  */
+  struct ts_linecol visi_end_linecol;
   /* This counter is incremented every time a change is made to the
      buffer in treesit_record_change.  The node retrieved from this parser
      inherits this timestamp.  This way we can make sure the node is
@@ -222,7 +231,19 @@ CHECK_TS_COMPILED_QUERY (Lisp_Object query)
 
 INLINE_HEADER_END
 
-extern void treesit_record_change (ptrdiff_t, ptrdiff_t, ptrdiff_t);
+/* A linecol_cache that points to BOB, this is always valid.  */
+static const struct ts_linecol TREESIT_BOB_LINECOL = { 1, 1, 1, 0 };
+/* An uninitialized linecol.  */
+static const struct ts_linecol TREESIT_EMPTY_LINECOL = { 0, 0, 0, 0 };
+static const TSPoint TREESIT_TS_POINT_1_0 = { 1, 0 };
+
+extern struct ts_linecol linecol_offset (struct ts_linecol,
+                                         struct ts_linecol);
+extern struct ts_linecol treesit_linecol_maybe (ptrdiff_t, ptrdiff_t,
+                                                struct ts_linecol);
+extern void treesit_record_change (ptrdiff_t, ptrdiff_t, ptrdiff_t,
+                                   struct ts_linecol, struct ts_linecol,
+                                   ptrdiff_t);
 extern Lisp_Object make_treesit_parser (Lisp_Object, TSParser *, TSTree *,
                                         Lisp_Object, Lisp_Object);
 extern Lisp_Object make_treesit_node (Lisp_Object, TSNode);
diff --git a/test/src/treesit-tests.el b/test/src/treesit-tests.el
index caacb74315d..11d5e1b2c8c 100644
--- a/test/src/treesit-tests.el
+++ b/test/src/treesit-tests.el
@@ -224,6 +224,51 @@
       (kill-buffer base)
       (kill-buffer indirect))))
 
+;;; Linecol
+
+(ert-deftest treesit-linecol-basic ()
+  "Tests for basic lincol synchronization."
+  (with-temp-buffer
+    (should (equal (treesit--linecol-cache)
+                   '(:line 1 :col 0 :pos 1 :bytepos 1)))
+    (should (equal (treesit--linecol-at (point))
+                   '(1 . 0)))
+    (insert "\n")
+    ;; Buffer content: a single newline.
+    (should (equal (treesit--linecol-at (point))
+                   '(2 . 0)))
+
+    (treesit--linecol-cache-set 2 0 2 2)
+    (should (equal (treesit--linecol-cache)
+                   '(:line 2 :col 0 :pos 2 :bytepos 2)))
+
+    (goto-char (point-min))
+    (should (equal (treesit--linecol-at (point))
+                   '(1 . 0)))
+
+    (insert "0123456789")
+    ;; Buffer content: ten chars followed by a newline.
+    (treesit--linecol-cache-set 1 0 1 1)
+    (should (equal (treesit--linecol-at (point))
+                   '(1 . 10)))
+
+    (goto-char (point-max))
+    (should (equal (treesit--linecol-at (point))
+                   '(2 . 0)))
+
+    (treesit--linecol-cache-set 1 5 6 6)
+    (should (equal (treesit--linecol-at (point))
+                   '(2 . 0)))
+
+    (treesit--linecol-cache-set 2 0 12 12)
+    ;; Position 6 is in the middle of the first line.
+    (should (equal (treesit--linecol-at 6)
+                   '(1 . 5)))
+    ;; Position 11 is at the end of the line.
+    (should (equal (treesit--linecol-at 11)
+                   '(1 . 10)))
+    ))
+
 ;;; Tree traversal
 
 (ert-deftest treesit-search-subtree ()