linux-kernel - [PATCH 08/11] vt: support Unicode recomposition

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Message-ID: <20250410011839.64418-9-nico@fluxnic.net>
Date: Wed,  9 Apr 2025 21:14:00 -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>,
	Dave Mielke <Dave@...lke.cc>,
	linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 08/11] vt: support Unicode recomposition

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

Try replacing any decomposed Unicode sequence by the corresponding
recomposed code point. Code point to glyph correspondance works best
after recomposition, and this apply mostly to single-width code points
therefore we can't preserve them in their decomposed form anyway.

With all the infrastructure in place this is now trivial to do.

Signed-off-by: Nicolas Pitre <npitre@...libre.com>
---
 drivers/tty/vt/vt.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 5d53feeb5d..e3d35c4f92 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2953,8 +2953,15 @@ static int vc_con_write_normal(struct vc_data *vc, int tc, int c,
 				 * double-width.
 				 */
 			} else {
-				/* Otherwise zero-width code points are ignored */
-				goto out;
+				/* try recomposition */
+				prev_c = ucs_recompose(prev_c, c);
+				if (prev_c != 0) {
+					vc_con_rewind(vc);
+					c = prev_c;
+				} else {
+					/* Otherwise zero-width code points are ignored */
+					goto out;
+				}
 			}
 		}
 	}
-- 
2.49.0