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Message-ID: <YfFU9Dp1Bfa4Ljss@kroah.com>
Date: Wed, 26 Jan 2022 15:04:36 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: nick black <dankamongmen@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Daniel Vetter <daniel.vetter@...ll.ch>,
linux-kernel@...r.kernel.org,
Thomas Dickey <dickey@...isible-island.net>
Subject: Re: [PATCH v2] console: answer OSC 10 and 11
On Mon, Jan 24, 2022 at 12:49:26AM -0500, nick black wrote:
> XTerm and many other terminal emulators implement
> Operating System Commands 10 and 11, allowing the
> default foreground/background to be set and queried.
> Extend the VT control sequence parser to recognize
> and support these queries.
Nit, can you use the full 72 columns here?
> The VT already implements two OSCs, for changing
> and resetting the palette. In doing so (many years
> ago), it broke from the ANSI standard, and did not
> require an ST terminator. Read all about it in
> xterm(1) (see "brokenLinuxOSC"). I have followed this
> grand tradition, and similarly not required ST.
> Note that ST can still be safely sent by a client
> program, as the VT consumes it. Indeed, my Notcurses
> library does exactly this.
>
> "Don't VTs always have black backgrounds?" Nope, you
> can change the default background color with any
> number of ANSI sequences, and then use the VT's
> Private CSI "ESC [ 8 ]" to make the current color pair
> the default attributes. Try it at home with, say:
>
> printf %b '\e[46m' '\e[8]' '\e[H\e[J'
>
> The response follows XTerm's effective lead, using
> %02x/%02x/%02x to format the RGB value, rather than
> the %02x%02x%02x preferred by the preexisting
> P (set palette) OSC. This was done to simplify
> client libraries. Note that the spirit of the law,
> that the reply is a "control sequence of the same
> form which can be used to set", cannot be easily
> honored given the semantics of the Linux private CSI
> sequence. So it goes.
>
> As a result, notcurses-info now properly detects the
> default colors dynamically. Where it used to say:
>
> no known default fg no known default bg
>
> It now says on boot:
>
> notcurses 3.0.4 on Linux 5.16.0nlb VT
> ...
> default fg 0xaaaaaa default bg 0x000000
>
> and after a change like that above:
>
> notcurses 3.0.4 on Linux 5.16.0nlb VT
> ...
> default fg 0xaaaaaa default bg 0xaa5500
>
> This is necessary to produce readable multicolor text
> while respecting the user's background choice.
>
> Signed-off-by: nick black <dankamongmen@...il.com>
> ---
> Changes in v2:
> - Reverse in-kernel BGR to RGB
>
> drivers/tty/vt/vt.c | 67 ++++++++++++++++++++++++++++------
> include/linux/console_struct.h | 1 +
> 2 files changed, 58 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index f8c87c4d7399..a10629bcaaa1 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -1878,6 +1878,31 @@ int mouse_reporting(void)
> return vc_cons[fg_console].d->vc_report_mouse;
> }
>
> +/* handle the OSC query specified by vc->vc_oscmd. we currently handle only 10
> + * and 11 (default foreground and default background, respectively).
> + */
> +static void handle_osc_query(struct tty_struct *tty, const struct vc_data *vc)
> +{
> + char buf[20];
> + int len, idx;
> + /* response payload conforms to XTerm: %02x/%02x/%02x for R, G, and B. */
Nit, new line needed after variable list.
> + switch (vc->vc_oscmd) {
> + case 10: /* get default foreground */
> + idx = vc->vc_def_color & 0x0f;
> + break;
> + case 11: /* get default background */
> + idx = (vc->vc_def_color & 0xf0) >> 4;
> + break;
Does 10 and 11 have a #define or enum anywhere?
> + default:
> + return;
No need to return an error? Why not?
> + }
> + /* transpose internal BGR to RGB on output */
> + len = snprintf(buf, sizeof(buf), "\x1b]%d;rgb:%02x/%02x/%02x\x1b\\",
> + vc->vc_oscmd, vc->vc_palette[idx * 3 + 2],
> + vc->vc_palette[idx * 3 + 1], vc->vc_palette[idx * 3]);
> + respond_string(buf, len, tty->port);
> +}
> +
> /* console_lock is held */
> static void set_mode(struct vc_data *vc, int on_off)
> {
> @@ -2075,8 +2100,8 @@ static void restore_cur(struct vc_data *vc)
> }
>
> enum { ESnormal, ESesc, ESsquare, ESgetpars, ESfunckey,
> - EShash, ESsetG0, ESsetG1, ESpercent, EScsiignore, ESnonstd,
> - ESpalette, ESosc, ESapc, ESpm, ESdcs };
> + EShash, ESsetG0, ESsetG1, ESpercent, EScsiignore,
> + ESpalette, ESosc, ESoscmd, ESoscparam, ESapc, ESpm, ESdcs };
>
> /* console_lock is held (except via vc_init()) */
> static void reset_terminal(struct vc_data *vc, int do_clear)
> @@ -2230,7 +2255,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
> vc->vc_state = ESsquare;
> return;
> case ']':
> - vc->vc_state = ESnonstd;
> + vc->vc_state = ESosc;
> return;
> case '_':
> vc->vc_state = ESapc;
> @@ -2287,7 +2312,10 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
> return;
> }
> return;
> - case ESnonstd:
> + case ESosc:
> + /* Operating System Commands are traditionally terminated with an ST
> + * or a BEL, but Linux historically eschews said terminators.
> + */
> if (c=='P') { /* palette escape sequence */
> for (vc->vc_npar = 0; vc->vc_npar < NPAR; vc->vc_npar++)
> vc->vc_par[vc->vc_npar] = 0;
> @@ -2297,9 +2325,10 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
> } else if (c=='R') { /* reset palette */
> reset_palette(vc);
> vc->vc_state = ESnormal;
> - } else if (c>='0' && c<='9')
> - vc->vc_state = ESosc;
> - else
> + } else if (isdigit(c)) {
> + vc->vc_oscmd = c - '0';
> + vc->vc_state = ESoscmd;
We used to jump to ESosc here, what happened to that if the command is
invalid?
> + } else
> vc->vc_state = ESnormal;
> return;
> case ESpalette:
> @@ -2348,7 +2377,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
> if (c == ';' && vc->vc_npar < NPAR - 1) {
> vc->vc_npar++;
> return;
> - } else if (c>='0' && c<='9') {
> + } else if (isdigit(c)) {
Different change, you can put this in a different patch.
thanks,
greg k-h
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