kitty diff kitten can sometimes exhibit repainting issues

[salmankhilji]

Describe the bug
kitty diff kitten can sometimes show a white screen. This may be sensitive to the current scroll position and the length of the input, so I am providing a simple git repo for easy repro.

To Reproduce
Steps to reproduce the behavior:

1. Download this toy git repo and extract to some temporary directory.

2. Launch kitty without any config:

   kitty -c NONE
   

3. cd into the git repo.

4. Launch the kitty:

   git difftool --no-symlinks --dir-diff 9add876^!
   

5. Press the following key combos: END (to scroll to end), then a (to show all context), and then finally END again.

Observed Behavior

A white screen. I can scroll up and down with the arrow keys and parts of the screen that scroll back into the screen are repainted correctly.

Screenshots
Here is a screencast of the issue. You can play it with the asciinema tool, like this:

asciinema play bug.cast

Environment details

kitty 0.24.4 created by Kovid Goyal
Linux byteevo-scm 5.13.0-35-generic #40~20.04.1-Ubuntu SMP Mon Mar 7 09:18:32 UTC 2022 x86_64
Ubuntu 20.04.4 LTS byteevo-scm /dev/tty

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04.4 LTS"
Running under: X11
Frozen: True
Paths:
  kitty: /home/precor/.local/kitty.app/bin/kitty
  base dir: /home/precor/.local/kitty.app/lib/kitty
  extensions dir: /home/precor/.local/kitty.app/lib/kitty-extensions
  system shell: /bin/bash

Config options different from defaults:

Important environment variables seen by the kitty process:
	PATH                                /home/precor/.nvm/versions/node/v14.18.2/bin:/opt/qt/5.15.2/gcc_64/bin:/home/precor/Android/Sdk/build-tools/30.0.3:/home/precor/Android/Sdk/emulator:/home/precor/Android/Sdk/platform-tools:/home/precor/Android/Sdk/cmdline-tools/latest/bin:/home/precor/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/precor/.local/flutter/bin:/home/precor/.pub-cache/bin
	LANG                                en_US.UTF-8
	SHELL                               /bin/bash
	DISPLAY                             :0
	USER                                precor
	XDG_CONFIG_DIRS                     /etc/xdg/xdg-ubuntu:/etc/xdg
	XDG_MENU_PREFIX                     gnome-
	XDG_SESSION_DESKTOP                 ubuntu
	XDG_SESSION_TYPE                    x11
	XDG_CURRENT_DESKTOP                 ubuntu:GNOME
	XDG_SESSION_CLASS                   user
	XDG_RUNTIME_DIR                     /run/user/1000
	XDG_DATA_DIRS                       /usr/share/ubuntu:/usr/local/share/:/usr/share/

Additional context

$ cat ~/.gitconfig 
[user]
	name = Salman A. Khilji
	email = salman.khilji@byteevo.com
[fetch]
	prune = true
[log]
	decorate = no
[color]
	ui = auto
[color "status"]
	branch = green
[diff]
	tool = kitty
	guitool = kitty.gui
	trustExitCode = true
[difftool "kitty"]
	cmd = kitty +kitten diff $LOCAL $REMOTE
[difftool "kitty.gui"]
	cmd = kitty --start-as=fullscreen kitty +kitten diff $LOCAL $REMOTE
[credential]
	helper = /usr/share/doc/git/contrib/credential/libsecret/git-credential-libsecret

[salmankhilji]

Oddly enough, the screencast I attached does not play within kitty itself for some reason.

I can play it just fine using GNOME Terminal.

For best results, the terminal size must be 128x32.