Date: Sat, 21 Oct 2023 14:35:45 GMT From: Christos Margiolis <christos@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: f859afb57fd8 - stable/13 - tty: fix improper backspace behaviour for UTF8 characters when in canonical mode Message-ID: <202310211435.39LEZjOh087514@gitrepo.freebsd.org>
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The branch stable/13 has been updated by christos: URL: https://cgit.FreeBSD.org/src/commit/?id=f859afb57fd87715ab80fc00635016949a5daf0e commit f859afb57fd87715ab80fc00635016949a5daf0e Author: Bojan Novković <bojan.novkovic@fer.hr> AuthorDate: 2023-10-07 18:00:11 +0000 Commit: Christos Margiolis <christos@FreeBSD.org> CommitDate: 2023-10-21 14:34:21 +0000 tty: fix improper backspace behaviour for UTF8 characters when in canonical mode This patch adds additional logic in ttydisc_rubchar() to properly handle backspace behaviour for UTF-8 characters. Currently, typing in a backspace after a UTF8 character will delete only one byte from the byte sequence, leaving garbled output in the tty's output queue. With this change all of the character's bytes are deleted. This change is only active when the IUTF8 flag is set (see 19054eb6053189144aa962b2ecc1bf5087758a3e "(s)tty: add support for IUTF8 input flag") The code uses the teken_wcwidth() function to properly handle character column widths for different code points, and adds the teken_utf8_bytes_to_codepoint() function that converts a UTF-8 byte sequence to a codepoint, as specified in RFC3629. Reported by: christos Reviewed by: christos, imp MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D42067 (cherry picked from commit 9e589b0938579f3f4d89fa5c051f845bf754184d) --- sys/kern/tty_ttydisc.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++ sys/teken/teken_wcwidth.h | 30 +++++++++++++++++++ 2 files changed, 104 insertions(+) diff --git a/sys/kern/tty_ttydisc.c b/sys/kern/tty_ttydisc.c index 665275ee93e7..eae7162e31c0 100644 --- a/sys/kern/tty_ttydisc.c +++ b/sys/kern/tty_ttydisc.c @@ -43,6 +43,9 @@ #include <sys/uio.h> #include <sys/vnode.h> +#include <teken/teken.h> +#include <teken/teken_wcwidth.h> + /* * Standard TTYDISC `termios' line discipline. */ @@ -78,8 +81,13 @@ SYSCTL_ULONG(_kern, OID_AUTO, tty_nout, CTLFLAG_RD, /* Character is alphanumeric. */ #define CTL_ALNUM(c) (((c) >= '0' && (c) <= '9') || \ ((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z')) +/* Character is UTF8-encoded. */ +#define CTL_UTF8(c) (!!((c) & 0x80)) +/* Character is a UTF8 continuation byte. */ +#define CTL_UTF8_CONT(c) (((c) & 0xc0) == 0x80) #define TTY_STACKBUF 256 +#define UTF8_STACKBUF 4 void ttydisc_open(struct tty *tp) @@ -800,6 +808,72 @@ ttydisc_rubchar(struct tty *tp) ttyoutq_write_nofrag(&tp->t_outq, "\b\b\b\b\b\b\b\b", tablen); return (0); + } else if ((tp->t_termios.c_iflag & IUTF8) != 0 && + CTL_UTF8(c)) { + uint8_t bytes[UTF8_STACKBUF] = { 0 }; + int curidx = UTF8_STACKBUF - 1, cwidth = 1, + nb = 0; + teken_char_t codepoint; + + /* Save current byte. */ + bytes[curidx] = c; + curidx--; + nb++; + /* Loop back through inq until we hit the + * leading byte. */ + while (CTL_UTF8_CONT(c) && nb < UTF8_STACKBUF) { + ttyinq_peekchar(&tp->t_inq, &c, "e); + ttyinq_unputchar(&tp->t_inq); + bytes[curidx] = c; + curidx--; + nb++; + } + /* + * Shift array so that the leading + * byte ends up at idx 0. + */ + if (nb < UTF8_STACKBUF) + memmove(&bytes[0], &bytes[curidx + 1], + nb * sizeof(uint8_t)); + /* Check for malformed UTF8 characters. */ + if (nb == UTF8_STACKBUF && + CTL_UTF8_CONT(bytes[0])) { + /* + * Place all bytes back into the inq and + * delete the last byte only. + */ + ttyinq_write(&tp->t_inq, bytes, + UTF8_STACKBUF, 0); + } else { + /* Find codepoint and width. */ + codepoint = + teken_utf8_bytes_to_codepoint(bytes, + nb); + if (codepoint != + TEKEN_UTF8_INVALID_CODEPOINT) { + cwidth = teken_wcwidth( + codepoint); + } else { + /* + * Place all bytes back into the + * inq and fall back to + * default behaviour. + */ + ttyinq_write(&tp->t_inq, bytes, + nb, 0); + } + } + tp->t_column -= cwidth; + /* + * Delete character by punching + * 'cwidth' spaces over it. + */ + if (cwidth == 1) + ttyoutq_write_nofrag(&tp->t_outq, + "\b \b", 3); + else if (cwidth == 2) + ttyoutq_write_nofrag(&tp->t_outq, + "\b\b \b\b", 6); } else { /* * Remove a regular character by diff --git a/sys/teken/teken_wcwidth.h b/sys/teken/teken_wcwidth.h index f57a185c2433..f5a23dbc9679 100644 --- a/sys/teken/teken_wcwidth.h +++ b/sys/teken/teken_wcwidth.h @@ -8,6 +8,8 @@ * Latest version: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c */ +#define TEKEN_UTF8_INVALID_CODEPOINT -1 + struct interval { teken_char_t first; teken_char_t last; @@ -116,3 +118,31 @@ static int teken_wcwidth(teken_char_t ucs) (ucs >= 0x20000 && ucs <= 0x2fffd) || (ucs >= 0x30000 && ucs <= 0x3fffd))); } + +/* + * Converts an UTF-8 byte sequence to a codepoint as specified in + * https://datatracker.ietf.org/doc/html/rfc3629#section-3 . The function + * expects the 'bytes' array to start with the leading character. + */ +static teken_char_t +teken_utf8_bytes_to_codepoint(uint8_t bytes[4], int nbytes) +{ + + /* Check for malformed characters. */ + if (bitcount(bytes[0] & 0xf0) != nbytes) + return (TEKEN_UTF8_INVALID_CODEPOINT); + + switch (nbytes) { + case 1: + return (bytes[0] & 0x7f); + case 2: + return (bytes[0] & 0xf) << 6 | (bytes[1] & 0x3f); + case 3: + return (bytes[0] & 0xf) << 12 | (bytes[1] & 0x3f) << 6 | (bytes[2] & 0x3f); + case 4: + return (bytes[0] & 0x7) << 18 | (bytes[1] & 0x3f) << 12 | + (bytes[2] & 0x3f) << 6 | (bytes[3] & 0x3f); + default: + return (TEKEN_UTF8_INVALID_CODEPOINT); + } +}
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