Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 21:36:28 -0600 Brian Inglis wrote: > So how do you tell the pseudo-console to generate only text not escape > sequences > the recipient may not be prepared to deal with? Unfortunately, no idea. -- Takashi Yano
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On 2019-09-04 19:13, Takashi Yano wrote:
> On Wed, 4 Sep 2019 11:22:42 -0600
> Brian Inglis wrote:
>> That output seems to be generated by a shell or program running in the pty.
>> If the recipient can not handle escape sequences, then the shell or program
>> in
>> the pty should be configured by setting e.g. TERM=dumb when launching the
>> terminal, or in the shell environment.
>
> No. Output is almost same even if setting TERM=dumb.
> See attached log.
>
> Consider what should be the output of pseudo console if console
> application like below is executed.
>
> #include
>
> int main()
> {
> HANDLE h = GetStdHandle(STD_OUTPUT_HANDLE);
> COORD p = {20, 10};
> DWORD n;
> SetConsoleCursorPosition(h, p);
> SetConsoleTextAttribute(h, FOREGROUND_RED);
> WriteConsole(h, "R", 1, &n, 0);
> SetConsoleTextAttribute(h, FOREGROUND_GREEN);
> WriteConsole(h, "G", 1, &n, 0);
> SetConsoleTextAttribute(h, FOREGROUND_BLUE);
> WriteConsole(h, "B", 1, &n, 0);
> SetConsoleTextAttribute(h,
> FOREGROUND_RED|FOREGROUND_GREEN|FOREGROUND_BLUE);
> WriteConsole(h, "W", 1, &n, 0);
> WriteConsole(h, "\r\n", 2, &n, 0);
> return 0;
> }
>
> Setting cursor posision and text color cannot be realized
> without ANSI escape sequences.
>
> Indeed, the output of the pseudo console by the program above is:
> ^[[?25l^[[11;21H^[[?25h^[[?25l^[[31mR^[[32mG^[[34mB^[[mW^M
> ^[[?25h
So how do you tell the pseudo-console to generate only text not escape sequences
the recipient may not be prepared to deal with?
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
This email may be disturbing to some readers as it contains
too much technical detail. Reader discretion is advised.
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 11:22:42 -0600
Brian Inglis wrote:
> That output seems to be generated by a shell or program running in the pty.
> If the recipient can not handle escape sequences, then the shell or program in
> the pty should be configured by setting e.g. TERM=dumb when launching the
> terminal, or in the shell environment.
No. Output is almost same even if setting TERM=dumb.
See attached log.
Consider what should be the output of pseudo console if console
application like below is executed.
#include
int main()
{
HANDLE h = GetStdHandle(STD_OUTPUT_HANDLE);
COORD p = {20, 10};
DWORD n;
SetConsoleCursorPosition(h, p);
SetConsoleTextAttribute(h, FOREGROUND_RED);
WriteConsole(h, "R", 1, &n, 0);
SetConsoleTextAttribute(h, FOREGROUND_GREEN);
WriteConsole(h, "G", 1, &n, 0);
SetConsoleTextAttribute(h, FOREGROUND_BLUE);
WriteConsole(h, "B", 1, &n, 0);
SetConsoleTextAttribute(h, FOREGROUND_RED|FOREGROUND_GREEN|FOREGROUND_BLUE);
WriteConsole(h, "W", 1, &n, 0);
WriteConsole(h, "\r\n", 2, &n, 0);
return 0;
}
Setting cursor posision and text color cannot be realized
without ANSI escape sequences.
Indeed, the output of the pseudo console by the program above is:
^[[?25l^[[11;21H^[[?25h^[[?25l^[[31mR^[[32mG^[[34mB^[[mW^M
^[[?25h
--
Takashi Yano
pcon-output-dumb.log
Description: Binary data
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On 2019-09-03 21:45, Takashi Yano wrote: > On Wed, 4 Sep 2019 12:34:31 +0900 > Takashi Yano wrote: >> Attached is the raw output from pseudo console when the screen shows >> the simple text below. >> >> from here >> [yano@Express5800-S70 ~]$ cmd >> Microsoft Windows [Version 10.0.18362.329] >> (c) 2019 Microsoft Corporation. All rights reserved. >> >> C:\cygwin\home\yano>exit >> [yano@Express5800-S70 ~]$ exit >> exit >> to here >> >> You will noticed that the screen is cleared if you execute >> cat pcon-output.log >> in a terminal which support ANSI escape sequences. > > This pcon-output.log was recorded in screen of 80x24 size. > Please try above in 80x24 terminal. That output seems to be generated by a shell or program running in the pty. If the recipient can not handle escape sequences, then the shell or program in the pty should be configured by setting e.g. TERM=dumb when launching the terminal, or in the shell environment. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 17:19:05 +0200 Corinna Vinschen wrote: > > But the first check (the one in fixup_after_attach()) could be dropped, > > couldn't it? > > IIUC the second test first checks for need_clear_screen but then the > TERM might have changed in the meantime which in turn requires to change > the behaviour again. But yeah, this sound like the first patch is not > actually required at all. I was convinced. I will revise the patch. -- Takashi Yano
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Sep 4 15:11, Ken Brown wrote: > On 9/4/2019 10:42 AM, Takashi Yano wrote: > > On Wed, 4 Sep 2019 15:55:03 +0200 > > Corinna Vinschen wrote: > >> The code in fixup_after_attach() is the only code snippet setting > >> need_clear_screen = true. And that code also requires term != "dump" && > >> term == "*emacs*" to set need_clear_screen. > > > > term != "*emacs*" > > > >> The code in reset_switch_to_pcon() requires that the need_clear_screen > >> flag is true regardless of checking TERM. So this code depends on the > >> successful TERM check from fixup_after_attach anyway. > >> > >> What am I missing? > > > > Two checking results may not be the same. Indeed, emacs changes > > TERM between two checks. > > > > fixup_after_attach() is called from fixup_after_exec(), > > which is called before executing the program code. > > reset_switch_to_pcon () is mainly called from PTY slave I/O functions. > > This is usually from the program code. > > But the first check (the one in fixup_after_attach()) could be dropped, > couldn't it? IIUC the second test first checks for need_clear_screen but then the TERM might have changed in the meantime which in turn requires to change the behaviour again. But yeah, this sound like the first patch is not actually required at all. Corinna -- Corinna Vinschen Cygwin Maintainer signature.asc Description: PGP signature
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On 9/4/2019 10:42 AM, Takashi Yano wrote: > On Wed, 4 Sep 2019 15:55:03 +0200 > Corinna Vinschen wrote: >> The code in fixup_after_attach() is the only code snippet setting >> need_clear_screen = true. And that code also requires term != "dump" && >> term == "*emacs*" to set need_clear_screen. > > term != "*emacs*" > >> The code in reset_switch_to_pcon() requires that the need_clear_screen >> flag is true regardless of checking TERM. So this code depends on the >> successful TERM check from fixup_after_attach anyway. >> >> What am I missing? > > Two checking results may not be the same. Indeed, emacs changes > TERM between two checks. > > fixup_after_attach() is called from fixup_after_exec(), > which is called before executing the program code. > reset_switch_to_pcon () is mainly called from PTY slave I/O functions. > This is usually from the program code. But the first check (the one in fixup_after_attach()) could be dropped, couldn't it? Ken
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 15:55:03 +0200 Corinna Vinschen wrote: > The code in fixup_after_attach() is the only code snippet setting > need_clear_screen = true. And that code also requires term != "dump" && > term == "*emacs*" to set need_clear_screen. term != "*emacs*" > The code in reset_switch_to_pcon() requires that the need_clear_screen > flag is true regardless of checking TERM. So this code depends on the > successful TERM check from fixup_after_attach anyway. > > What am I missing? Two checking results may not be the same. Indeed, emacs changes TERM between two checks. fixup_after_attach() is called from fixup_after_exec(), which is called before executing the program code. reset_switch_to_pcon () is mainly called from PTY slave I/O functions. This is usually from the program code. The behaviour of the patch is as follows. First check : True True False False Second check: True False True False Clear screen: Yes NoNo No # True: neither dumb nor emacs* # False: either dumb or emacs* > + if (get_ttyp ()->num_pcon_attached_slaves == 0 && > + term && strcmp (term, "dumb") && > + term && !strstr (term, "emacs") && > + !ALWAYS_USE_PCON) > > You're checking term for != NULL twice. Oh my! -- Takashi Yano
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Sep 4 21:49, Takashi Yano wrote: > On Wed, 4 Sep 2019 12:47:38 +0200 > Corinna Vinschen wrote: > > Why do you check the TERMs again here? After all, need_clear_screen > > is only true if one of these terms are used. > > Because, emacs seems to set environment TERM after fixup_after_exec() > is called. At the first check, TERM has the value of the terminal > in which emacs is executed. The first check is just in case. I still don't get it. The code in fixup_after_attach() is the only code snippet setting need_clear_screen = true. And that code also requires term != "dump" && term == "*emacs*" to set need_clear_screen. The code in reset_switch_to_pcon() requires that the need_clear_screen flag is true regardless of checking TERM. So this code depends on the successful TERM check from fixup_after_attach anyway. What am I missing? While at it, in fixup_after_attach(): + if (get_ttyp ()->num_pcon_attached_slaves == 0 && + term && strcmp (term, "dumb") && + term && !strstr (term, "emacs") && + !ALWAYS_USE_PCON) You're checking term for != NULL twice. Thanks, Corinna -- Corinna Vinschen Cygwin Maintainer signature.asc Description: PGP signature
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 12:47:38 +0200 Corinna Vinschen wrote: > Why do you check the TERMs again here? After all, need_clear_screen > is only true if one of these terms are used. Because, emacs seems to set environment TERM after fixup_after_exec() is called. At the first check, TERM has the value of the terminal in which emacs is executed. The first check is just in case. -- Takashi Yano
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Sep 4 10:46, Takashi Yano wrote:
> - Pseudo console support introduced by commit
> 169d65a5774acc76ce3f3feeedcbae7405aa9b57 shows garbage ^[[H^[[J in
> some of emacs screens. These screens do not handle ANSI escape
> sequences. Therefore, clear screen is disabled on these screens.
> ---
> winsup/cygwin/fhandler_tty.cc | 26 +++---
> winsup/cygwin/tty.cc | 1 +
> winsup/cygwin/tty.h | 1 +
> 3 files changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
> index 283558985..a74c3eecf 100644
> --- a/winsup/cygwin/fhandler_tty.cc
> +++ b/winsup/cygwin/fhandler_tty.cc
> @@ -972,6 +972,19 @@ skip_console_setting:
> void
> fhandler_pty_slave::reset_switch_to_pcon (void)
> {
> + if (get_ttyp ()->need_clear_screen)
> +{
> + const char *term = getenv ("TERM");
> + if (term && strcmp (term, "dumb") && !strstr (term, "emacs"))
Why do you check the TERMs again here? After all, need_clear_screen
is only true if one of these terms are used.
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
signature.asc
Description: PGP signature
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On Wed, 4 Sep 2019 12:34:31 +0900 Takashi Yano wrote: > Attached is the raw output from pseudo console when the screen shows > the simple text below. > > from here > [yano@Express5800-S70 ~]$ cmd > Microsoft Windows [Version 10.0.18362.329] > (c) 2019 Microsoft Corporation. All rights reserved. > > C:\cygwin\home\yano>exit > [yano@Express5800-S70 ~]$ exit > exit > to here > > You will noticed that the screen is cleared if you execute > cat pcon-output.log > in a terminal which support ANSI escape sequences. This pcon-output.log was recorded in screen of 80x24 size. Please try above in 80x24 terminal. -- Takashi Yano
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
Hi Brian, On Tue, 3 Sep 2019 20:47:14 -0600 Brian Inglis wrote: > On 2019-09-03 19:46, Takashi Yano wrote: > > - Pseudo console support introduced by commit > > 169d65a5774acc76ce3f3feeedcbae7405aa9b57 shows garbage ^[[H^[[J in > > some of emacs screens. These screens do not handle ANSI escape > > sequences. Therefore, clear screen is disabled on these screens. > > Dealing with escape sequences is way out of the scope of any pty driver. > It is up to the terminal emulator or applications running in the terminal to > handle terminal characteristics appropriately. > > The pty driver should not touch *ANY* escape sequences coming from the system, > nor should it generate any to it, as TERM may not be set at the time, or > appropriately or usefully in some shells e.g. cmd or powershell. > > Most folks probably use mintty or cmd as their Cygwin terminal, but some use > other terminals, like various flavours of xterm and rxvt, with ssh sessions in > and out, so they could be on Linux consoles or proprietary AIX/HP-UX/Sun > terminals, and operate properly as long as they have a good terminfo > definition. > > I see this issue as similar to the Windows text file handling changes required > when coreutils/textutils went POSIX and removed '\r\n' crlf handling to give > the > same results as on Unix systems. > To handle terminal characteristics properly would require terminfo support in > the pty driver: I doubt anyone wants that, so the best approach is to do > nothing, and let the terminal or application handle it: they are more likely > to > have the configuration options or hooks to do so easily. You are definitely right. However, the essence of the problem is that the pseudo console itself outputs a lot of ANSI escape sequences even if client program output only ASCII characters. Attached is the raw output from pseudo console when the screen shows the simple text below. from here [yano@Express5800-S70 ~]$ cmd Microsoft Windows [Version 10.0.18362.329] (c) 2019 Microsoft Corporation. All rights reserved. C:\cygwin\home\yano>exit [yano@Express5800-S70 ~]$ exit exit to here You will noticed that the screen is cleared if you execute cat pcon-output.log in a terminal which support ANSI escape sequences. So clearing the screen when creating pseudo console is the result of compromise to synchronize real screen and screen buffer of pseudo console. -- Takashi Yano pcon-output.log Description: Binary data
Re: [PATCH 2/2] Cygwin: pty: Disable clear screen on new pty if TERM=dumb or emacs*.
On 2019-09-03 19:46, Takashi Yano wrote: > - Pseudo console support introduced by commit > 169d65a5774acc76ce3f3feeedcbae7405aa9b57 shows garbage ^[[H^[[J in > some of emacs screens. These screens do not handle ANSI escape > sequences. Therefore, clear screen is disabled on these screens. Dealing with escape sequences is way out of the scope of any pty driver. It is up to the terminal emulator or applications running in the terminal to handle terminal characteristics appropriately. The pty driver should not touch *ANY* escape sequences coming from the system, nor should it generate any to it, as TERM may not be set at the time, or appropriately or usefully in some shells e.g. cmd or powershell. Most folks probably use mintty or cmd as their Cygwin terminal, but some use other terminals, like various flavours of xterm and rxvt, with ssh sessions in and out, so they could be on Linux consoles or proprietary AIX/HP-UX/Sun terminals, and operate properly as long as they have a good terminfo definition. I see this issue as similar to the Windows text file handling changes required when coreutils/textutils went POSIX and removed '\r\n' crlf handling to give the same results as on Unix systems. To handle terminal characteristics properly would require terminfo support in the pty driver: I doubt anyone wants that, so the best approach is to do nothing, and let the terminal or application handle it: they are more likely to have the configuration options or hooks to do so easily. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.
