Page break (^L) doesn't clear terminal

Question

Page break (^L) doesn't clear terminal

Slider-Whistle opened this issue 5 years ago · comments

When the page break character is sent to the terminal, the normal functionality is to push it all up past the top row. Linux's native console does this, if you want to test.
With yaft though, at least for me, it only goes up by a single row, like a few naive terminal emulators. Are there any plans to fix this?

Slider-Whistle · Answer 1 · Sat Apr 06 2019 05:10:11 GMT+0800 (China Standard Time)

Oh, I should clarify, I'm using version 0.2.9. Should I just use the latest git version?

uobikiemukot · Answer 2 · Mon Apr 08 2019 10:39:33 GMT+0800 (China Standard Time)

Hi,

yaft normally erases display when receives Ctrl-L. Maybe some settings are incorrect.

Please check:

install yaft's terminfo before use: $ tic info/yaft.src
use correct TERM environment variable: $ export TERM=yaft-256color

You should use TERM=yaft-256color inside of terminal multiplexer (tmux or screen).

Slider-Whistle · Answer 3 · Mon Apr 08 2019 11:30:22 GMT+0800 (China Standard Time)

Tried installing the terminfo, it didn't seem to make a difference after restarting the program.
The TERM variable's correct, too. Is there anything else it could be?

uobikiemukot · Answer 4 · Mon Apr 08 2019 11:54:32 GMT+0800 (China Standard Time)

Some questions:

$ tput reset works correctly? (it behaves like Ctrl-L)
What kind of shell are you using?
Are you using terminal multiplier (tmux or screen or something) with yaft?

Please paste debug log here for more investigation.
It's very helpful.

set VERBOSE = true in conf.h
re-compile yaft
run $ yaft > dump 2> log
send Ctrl-L and exit
paste log here

Slider-Whistle · Answer 5 · Tue Apr 09 2019 10:08:18 GMT+0800 (China Standard Time)

tput reset does work
Nothing unusual, just using bash (version 4.3.048, seems to be a little outdated)
Nope

dump:
[mark@home-base ~]$
[mark@home-base ~]$ exit

log:

DEBUG<< framebuffer info:
DEBUG<< red(off:0 len:8) green(off:0 len:8) blue(off:0 len:8)
DEBUG<< resolution 1920x1080
DEBUG<< screen size:2076672 line length:1920
DEBUG<< bits_per_pixel:8 bytes_per_pixel:1
DEBUG<< type:YAFT_FB_TYPE_PACKED_PIXELS
DEBUG<< visual:YAFT_FB_VISUAL_PSEUDOCOLOR
DEBUG<< colors:256 max_length:8
DEBUG<< terminal cols:240 lines:67
DEBUG<< esc reset
DEBUG<< addch: U+005B
DEBUG<< addch: U+006D
DEBUG<< addch: U+0061
DEBUG<< addch: U+0072
DEBUG<< addch: U+006B
DEBUG<< addch: U+0040
DEBUG<< addch: U+0068
DEBUG<< addch: U+006F
DEBUG<< addch: U+006D
DEBUG<< addch: U+0065
DEBUG<< addch: U+002D
DEBUG<< addch: U+0062
DEBUG<< addch: U+0061
DEBUG<< addch: U+0073
DEBUG<< addch: U+0065
DEBUG<< addch: U+0020
DEBUG<< addch: U+007E
DEBUG<< addch: U+005D
DEBUG<< addch: U+0024
DEBUG<< addch: U+0020
DEBUG<< ctl: CR
DEBUG<< ctl: LF
DEBUG<< addch: U+005B
DEBUG<< addch: U+006D
DEBUG<< addch: U+0061
DEBUG<< addch: U+0072
DEBUG<< addch: U+006B
DEBUG<< addch: U+0040
DEBUG<< addch: U+0068
DEBUG<< addch: U+006F
DEBUG<< addch: U+006D
DEBUG<< addch: U+0065
DEBUG<< addch: U+002D
DEBUG<< addch: U+0062
DEBUG<< addch: U+0061
DEBUG<< addch: U+0073
DEBUG<< addch: U+0065
DEBUG<< addch: U+0020
DEBUG<< addch: U+007E
DEBUG<< addch: U+005D
DEBUG<< addch: U+0024
DEBUG<< addch: U+0020
DEBUG<< addch: U+0065
DEBUG<< addch: U+0078
DEBUG<< addch: U+0069
DEBUG<< addch: U+0074
DEBUG<< ctl: CR
DEBUG<< ctl: LF
DEBUG<< caught signal! no:17

Looks like it's interpreting ^L as "Enter" for some reason. Should I post my config? I don't think I changed much.

uobikiemukot · Answer 6 · Tue Apr 09 2019 12:57:58 GMT+0800 (China Standard Time)

Thank you for the information.

It seems that GNU Readline (line edit library used by bash) doesn't send correct terminal escape sequences. Normally it sends CSI H CSI J if receives Ctrl-L. This is clear sequences defined in yaft's terminfo. (and sorry, Ctrl-L equals $ tput clear not $ tput reset...)

process flow is like this:

user input Ctrl-L
readline check current key bindings for Ctrl-L
readline search terminfo and send clear sequences (CSI H CSI J)
yaft parse CSI H CSI J and erase display

Maybe 2 or 3 is something wrong.

Slider-Whistle · Answer 7 · Wed Apr 10 2019 05:39:03 GMT+0800 (China Standard Time)

I was using Readline version 6.3, while the latest is version 8. I upgraded to the latest version, but I'm still not getting any difference. I've confirmed that `tput clear` works, so I guess it's either something wrong with yaft's terminfo (unlikely, but maybe I should upgrade to the latest git version just in case?), or something wrong with Readline.

hackerb9 · Answer 8 · Sat Apr 13 2019 16:01:18 GMT+0800 (China Standard Time)

Since tput clear didn't say "unknown terminal", yaft's terminfo file is installed and is being used. The problem is with how your system is handling ^L.

Do you have a file called ~/.inputrc? That file lets you change how keys are interpreted by Readline, including clear-screen. Try running the command bind -p to see which key is bound to clear-screen.

$ bind -p | grep clear
"\C-l": clear-screen

The only other alternative I can think of that might be wrong would be if you somehow got your tty into raw mode, which shouldn't be a problem with bash. Try stty sane and see if it helps.

hackerb9 · Answer 9 · Sat Apr 13 2019 16:12:25 GMT+0800 (China Standard Time)

By the way, you don't happen to be using a remapped keyboard, do you? For example, Dvorak or some internationalization? And you've tried yaft without modifying the config file, right?

Slider-Whistle · Answer 10 · Sun Apr 14 2019 11:21:43 GMT+0800 (China Standard Time)

bind -p|grep clear

Returns ""\C-l": clear-screen". When I look at both /etc/inputrc or ~/.input rc, I don't see any mappings for \C-l, though, so I don't know what's going on there.

raw mode

The home, end, delete and arrow keys seem to work, so I don't know if that could be it. I tried stty sane and opened another shell within bash to see whether that'd help, but didn't get any changes. I would've changed the shell yaft starts with, but I don't know whether there's any way to do that without changing my settings.

remapped keyboard

I'm pretty sure I'm using a standard US keyboard mapping.

config file

Tried a fresh configuration file, no dice.

If nobody else ever encounters this, I'd be alright with just closing the issue and living with it. For probably future reference, I'm using the 64-bit version of Slackware 14.2.

hackerb9 · Answer 11 · Sun Apr 14 2019 13:36:05 GMT+0800 (China Standard Time)

You're probably right, it's just something to live with for now. It's downright weird, though. What if you bind a different key to clear? Perhaps ^O? Try running this command:

bind "\C-o":clear-screen

Slider-Whistle · Answer 12 · Mon Apr 15 2019 11:58:44 GMT+0800 (China Standard Time)

I tried that just now, it still just inserts a newline. There's an error on the actual terminal I saw after closing the program I might've not noticed earlier though, it says this: ">>ERROR<< put_cmap failed" Sounds pretty important, right?

uobikiemukot · Answer 13 · Wed Apr 17 2019 11:32:17 GMT+0800 (China Standard Time)

">>ERROR<< put_cmap failed"

I think this message is not related to erasing display.

put_cmap is called, If need to update hardware color palette at startup/terminate/vt-switch. If this error can be re-produced, it's an another bug 😢