patch 8.2.1509: vertical separator is cleared when dragging a popup window Commit: https://github.com/vim/vim/commit/9943b3d97955ece99c747c959e0a7d493bb762bb Author: Bram Moolenaar <Bram@vim.org> Date: Sat Aug 22 17:21:14 2020 +0200 patch 8.2.1509: vertical separator is cleared when dragging a popup window Problem: Vertical separator is cleared when dragging a popup window using a multi-byte character for the border. Solution: Only clear the character before the window if it is using a multi-byte character. (closes #6766)

--- a/src/screen.c
+++ b/src/screen.c
@@ -464,7 +464,8 @@ screen_line(
     // First char of a popup window may go on top of the right half of a
     // double-wide character. Clear the left half to avoid it getting the popup
     // window background color.
-    if (coloff > 0 && ScreenLines[off_to] == 0)
+    if (coloff > 0 && ScreenLines[off_to] == 0
+					     && ScreenLinesUC[off_to - 1] != 0)
     {
 	ScreenLines[off_to - 1] = ' ';
 	ScreenLinesUC[off_to - 1] = 0;