extmarks/bufhl: reimplement using new marktree data structure

Add new "splice" interface for tracking buffer changes at the byte
level. This will later be reused for byte-resolution buffer updates.
(Implementation has been started, but using undocumented "_on_bytes"
option now as interface hasn't been finalized).

Use this interface to improve many edge cases of extmark adjustment.
Changed tests indicate previously incorrect behavior. Adding tests for
more edge cases will be follow-up work (overlaps on_bytes tests)

Don't consider creation/deletion of marks an undoable event by itself.
This behavior was never documented, and imposes  complexity for little gain.

Add nvim__buf_add_decoration temporary API for direct access to the new
implementation. This should be refactored into a proper API for
decorations, probably involving a huge dict.

fixes #11598

1 files changed, 12 insertions, 0 deletions

diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index b193b4005c..addfab8f08 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -22,6 +22,7 @@
 #include "nvim/func_attr.h"
 #include "nvim/indent.h"
 #include "nvim/buffer_updates.h"
+#include "nvim/mark_extended.h"
 #include "nvim/mark.h"
 #include "nvim/memline.h"
 #include "nvim/memory.h"
@@ -1610,6 +1611,7 @@ static void foldAddMarker(linenr_T lnum, const char_u *marker, size_t markerlen)
   // Allocate a new line: old-line + 'cms'-start + marker + 'cms'-end
   line = ml_get(lnum);
   size_t line_len = STRLEN(line);
+  size_t added = 0;
 
   if (u_save(lnum - 1, lnum + 1) == OK) {
     // Check if the line ends with an unclosed comment
@@ -1619,12 +1621,19 @@ static void foldAddMarker(linenr_T lnum, const char_u *marker, size_t markerlen)
     // Append the marker to the end of the line
     if (p == NULL || line_is_comment) {
       STRLCPY(newline + line_len, marker, markerlen + 1);
+      added = markerlen;
     } else {
       STRCPY(newline + line_len, cms);
       memcpy(newline + line_len + (p - cms), marker, markerlen);
       STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
+      added = markerlen + STRLEN(cms)-2;
     }
     ml_replace(lnum, newline, false);
+    if (added) {
+      extmark_splice(curbuf, (int)lnum-1, (int)line_len,
+                     0, 0,
+                     0, (int)added, kExtmarkUndo);
+    }
   }
 }
 
@@ -1692,6 +1701,9 @@ static void foldDelMarker(linenr_T lnum, char_u *marker, size_t markerlen)
       memcpy(newline, line, (size_t)(p - line));
       STRCPY(newline + (p - line), p + len);
       ml_replace(lnum, newline, false);
+      extmark_splice(curbuf, (int)lnum-1, (int)(p - line),
+                     0, (int)len,
+                     0, 0, kExtmarkUndo);
     }
     break;
   }