vim-patch:9.1.1083: setreg() doesn't correctly handle mbyte chars in blockwise mode

Problem:  setreg() doesn't correctly handle mbyte chars in blockwise
          mode
Solution: use mb_ptr2len_len function pointer (Yee Cheng Chin)

setreg() will automatically calculate the width when a blockwise mode is
specified, but it does not properly calculate the line widths of mbyte
characters when value is passed as newline-terminated string. It does
work when value is passed as a list of lines though.

Fix this by properly using the mbyte function pointer to increment the
loop counter.

closes: vim/vim#16596

https://github.com/vim/vim/commit/a17f8bfb282805ee8ded014089d3094ef6dbf913

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 6c15d9a555..2491621fbc 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -5248,14 +5248,21 @@ static void str_to_reg(yankreg_T *y_ptr, MotionType yank_type, const char *str,
          start < end + extraline;
          start += line_len + 1, lnum++) {
       int charlen = 0;
-      const char *line_end;
-      for (line_end = start; line_end < end; line_end++) {
+
+      const char *line_end = start;
+      while (line_end < end) {  // find the end of the line
         if (*line_end == '\n') {
           break;
         }
         if (yank_type == kMTBlockWise) {
           charlen += utf_ptr2cells_len(line_end, (int)(end - line_end));
         }
+
+        if (*line_end == NUL) {
+          line_end++;  // registers can have NUL chars
+        } else {
+          line_end += utf_ptr2len_len(line_end, (int)(end - line_end));
+        }
       }
       assert(line_end - start >= 0);
       line_len = (size_t)(line_end - start);