patch 8.2.4660: cursorcolumn is sometimes not correctv8.2.4660

Problem:    Cursorcolumn is sometimes not correct.
Solution:   Recompute the cursor column when entering Insert mode and the
            cursor is on a character wider than a screen cell.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/edit.c b/src/edit.c
index 0edd38be4..c52583a8b 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -293,11 +293,14 @@ edit(
     conceal_check_cursor_line(cursor_line_was_concealed);
 #endif
 
-    /*
-     * Need to recompute the cursor position, it might move when the cursor is
-     * on a TAB or special character.
-     */
-    curs_columns(TRUE);
+    // Need to recompute the cursor position, it might move when the cursor
+    // is on a TAB or special character.
+    // ptr2cells() treats a TAB character as double-width.
+    if (ptr2cells(ml_get_cursor()) > 1)
+    {
+	curwin->w_valid &= ~VALID_VIRTCOL;
+	curs_columns(TRUE);
+    }
 
     /*
      * Enable langmap or IME, indicated by 'iminsert'.