fix(mbyte): fix bugs in utf_cp_*_off() functions

Problems:
- Illegal bytes after valid UTF-8 char cause utf_cp_*_off() to fail.
- When stream isn't NUL-terminated, utf_cp_*_off() may go over the end.
Solution: Don't go over end of the char of end of the string.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nvim/grid.c b/src/nvim/grid.c
index b6a8a8bd9f..e386853022 100644
--- a/src/nvim/grid.c
+++ b/src/nvim/grid.c
@@ -277,7 +277,7 @@ void line_do_arabic_shape(schar_T *buf, int cols)
       // Too bigly, discard one code-point.
       // This should be enough as c0 cannot grow more than from 2 to 4 bytes
       // (base arabic to extended arabic)
-      rest -= (size_t)utf_cp_head_off(scbuf + off, scbuf + off + rest - 1) + 1;
+      rest -= (size_t)utf_cp_bounds(scbuf + off, scbuf + off + rest - 1).begin_off + 1;
     }
     memcpy(scbuf_new + len, scbuf + off, rest);
     buf[i] = schar_from_buf(scbuf_new, len + rest);