commit 3a6d6d740110e6ee1b092d05ad746244eedabe4b
from: Shi Tian <shitian@cock.li>
via: Hiltjo Posthuma <hiltjo@codemadness.org>
date: Sun Jun 25 09:59:06 2023 UTC

Fix for wide character being incorrectly cleared on MODE_INSERT

Under insert mode, when inserting a normal character in front of
a wide character, the affected region is shifted to the right by
one cell. However, the empty cell is reset as if being a part of a
wide character, causing the following cell being mishandled as a
dummy cell.
To reproduce the bug:
	printf '\033[4h' # set MODE_INSERT
	printf 妳好
	printf '\033[4D'
	printf 'x'
	printf '\033[4l\n'

commit - 211964d56ee00a7d46e251cbc150afb79138ae37
commit + 3a6d6d740110e6ee1b092d05ad746244eedabe4b
blob - 134e7242e9b18d33dd82df401cbd266d9b9f30fd
blob + 623376e1b172781f66dd21ef220e165a8146eaad
--- st.c
+++ st.c
@@ -2471,8 +2471,10 @@ check_control_code:
 		gp = &term.line[term.c.y][term.c.x];
 	}
 
-	if (IS_SET(MODE_INSERT) && term.c.x+width < term.col)
+	if (IS_SET(MODE_INSERT) && term.c.x+width < term.col) {
 		memmove(gp+width, gp, (term.col - term.c.x - width) * sizeof(Glyph));
+		gp->mode &= ~ATTR_WIDE;
+	}
 
 	if (term.c.x+width > term.col) {
 		tnewline(1);