Kitty shuffles lines randomly in scrolling windows

[lindy2076]

Describe the bug When I use glow to view Markdown files or fzf with preview window I have problems with kitty rendering lines after scrolling.

I thought it was glow's issue but after installing fzf i encountered it again. I wrote an issue https://github.com/charmbracelet/glow/issues/554 where I described how to reproduce this bug. My guess is that kitty has problems rendering scrolling windows with some static window (glow has a small line of text in the bottom and fzf has a preview window on top). I use glow only in pager mode now (glow -p) because it doesn't produce "ghost" lines and don't shuffle them (it uses less). Also I was noticing "ghost" lines after exiting vim sometimes. My prompt showed the previous command vim *filename* but it was not real (it was replaced by the next command like if i had activated the insert mode in a text editor).

To Reproduce Steps to reproduce the behavior:

1. Install glow or fzf
2. Open long enough file and scroll fast.
3. See lines being shuffled randomly and ghost text.

Screenshots

glow

The original file is on the right. It is clear that glow messed some lines in the last paragraph (on the left):

But after going to the bottom by pressing G everything aligns normally (that's how the file on the right was opened)

fzf (large input, e.g. rg --files)

After some scrolling lines became messed up

But after reopening the preview window on top everything became normal.

exiting vim

Lines messed up. The cursor is on penultimate line (one line from the bottom)

Environment details

kitty 0.32.0 (eb5dd364ae) created by Kovid Goyal
Linux lindy-nb 6.5.0-14-generic #14~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Mon Nov 20 18:15:30 UTC 2 x86_64
Ubuntu 22.04.3 LTS lindy-nb /dev/tty

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.3 LTS"
Running under: X11
Frozen: True
Paths:
  kitty: /home/lindy/.local/kitty.app/bin/kitty
  base dir: /home/lindy/.local/kitty.app/lib/kitty
  extensions dir: /home/lindy/.local/kitty.app/lib/kitty-extensions
  system shell: /bin/bash
Loaded config files:
  /home/lindy/.config/kitty/kitty.conf

Config options different from defaults:
background_opacity   0.9
font_family          FiraCode Regular
window_padding_width FloatEdges(left=5.0, top=5.0, right=5.0, bottom=5.0)
Changed shortcuts:
    kitty_mod+n →  new_os_window, new_os_window_with_cwd
Colors:
    background           #2a3234   
    color0               #222627   
    color1               #ff6188   
    color10              #a9dc76   
    color11              #e9cb8b   
    color12              #fc9867   
    color13              #fa75c3   
    color14              #78dce8   
    color15              #fcfcfa   
    color2               #c5d157   
    color3               #e9cb8b   
    color4               #c79275   
    color5               #ad99dd   
    color6               #b7ebff   
    color7               #2a3234   
    color8               #6b8d89   
    color9               #f97683   
    cursor               #fcfcfa   
    cursor_text_color    #222627   
    foreground           #fcfcfa   
    selection_background #fcfcfa   
    selection_foreground #f98d9a   

Important environment variables seen by the kitty process:
    PATH                                /home/lindy/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/go/bin
    LANG                                en_US.UTF-8
    EDITOR                              vim
    SHELL                               /bin/bash
    DISPLAY                             :0
    USER                                lindy
    LC_TIME                             ru_RU.UTF-8
    XDG_SEAT                            seat0
    XDG_SESSION_TYPE                    tty
    LC_MONETARY                         ru_RU.UTF-8
    XDG_SESSION_CLASS                   user
    XDG_SESSION_ID                      1
    LC_ADDRESS                          ru_RU.UTF-8
    XDG_RUNTIME_DIR                     /run/user/1000
    LC_TELEPHONE                        ru_RU.UTF-8
    LC_NAME                             ru_RU.UTF-8
    LC_MEASUREMENT                      ru_RU.UTF-8
    LC_IDENTIFICATION                   ru_RU.UTF-8
    XDG_VTNR                            1
    XDG_DATA_DIRS                       /usr/share/gnome:/usr/local/share:/usr/share:/var/lib/snapd/desktop
    LC_NUMERIC                          ru_RU.UTF-8
    LC_PAPER                            ru_RU.UTF-8

Additional context Starting kitty with --config=none doesn't help, the problem is still present

[kovidgoyal]

kitty will render whatever the program running in it asks it to render. If you think there is some bug in how kitty renders thing come up with a reproducer that doesn't involve tons of other software. Chances are that software is simply doing something wrong, not following kitty's terminfo or using incorrect width calculations for unicode characters are the most common things software get wrong.

You can easily generate a reproducer by running kitty with --dump-bytes and doing the minimal amount of work to produce incorrect rendering. Then post the log generated by --dump-bytes alongwith the terminal size in cells in which it was generated.

When you do, I will take a look at it, but as I said chances are it is the client software not producing appropriate output. If the log is too large then analysing it will be too much work, and you will need to come up with a simpler reproducer.

[lindy2076]

Here it is, starting glow, switching the tab, selecting lorem ipsum md, scrolling till the end and then pressing G button to make lines look normally (288 lines) tput cols and tput lines output: 98 55

kitty_dump_bytes.gz

[kovidgoyal]

I need the log only till whatever point the render was corrupted. Simply close kitty at that point dont press G.

[lindy2076]

Same but closing after scrolling down kitty_dump2.gz

[kovidgoyal]

OK I'll look at it when I have some time

[lindy2076]

I managed to make it even shorter. So i just run rg --files | fzf --preview="xdg_prog {}" --bind="ctrl-space:toggle-preview" --preview-window=up,15% and scroll up a little.

xdg_prog is a bash script that echoes two lines:

MIME=$(xdg-mime query filetype "$1")
TOOL=$(xdg-mime query default $MIME)
echo -e "Opener: $TOOL\nmime: $MIME"

kitty-dump-fzf1234.gz

P.S. I tried to start only kitty with startx kitty and the bug was present

[kovidgoyal]

Dumping those bytes in xterm gives the exact same broken rendering, see attached screenshot. So not a kitty bug.

[lindy2076]

Yeah, indeed. I have this problem in gnome-terminal too... Thanks for help!