linux-kernel - [PATCH v2 2/8] vt: make sure displayed double-width characters are remembered as such

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Message-ID: <20250507141535.40655-3-nico@fluxnic.net>
Date: Wed,  7 May 2025 10:13:17 -0400
From: Nicolas Pitre <nico@...xnic.net>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>
Cc: Nicolas Pitre <npitre@...libre.com>,
	linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/8] vt: make sure displayed double-width characters are remembered as such

From: Nicolas Pitre <npitre@...libre.com>

And to do so we ensure the Unicode screen buffer is initialized when
double-width characters are encountered.

Signed-off-by: Nicolas Pitre <npitre@...libre.com>
---
 drivers/tty/vt/vt.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 24c6cd2eed78..58fa1b285f22 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2930,8 +2930,15 @@ static int vc_process_ucs(struct vc_data *vc, int *c, int *tc)
 {
 	u32 prev_c, curr_c = *c;
 
-	if (ucs_is_double_width(curr_c))
+	if (ucs_is_double_width(curr_c)) {
+		/*
+		 * The Unicode screen memory is allocated only when
+		 * required. This is one such case as we need to remember
+		 * which displayed characters are double-width.
+		 */
+		vc_uniscr_check(vc);
 		return 2;
+	}
 
 	if (!ucs_is_zero_width(curr_c))
 		return 1;
-- 
2.49.0