kitty/docs/faq.rst

Frequently Asked Questions
==============================

.. highlight:: sh

.. contents::

Some special symbols are rendered small/truncated in kitty?
-----------------------------------------------------------

The number of cells a unicode character takes up are controlled by the unicode
standard.  All characters are rendered in a single cell unless the unicode
standard says they should be rendered in two cells. When a symbol does not fit,
it will either be rescaled to be smaller or truncated (depending on how much
extra space it needs). This is often different from other terminals which just
let the character overflow into neighboring cells, which is fine if the
neighboring cell is empty, but looks terrible if it is not.

Some programs, like powerline, vim with fancy gutter symbols/status-bar, etc.
misuse unicode characters from the private use area to represent symbols. Often
these symbols are square and should be rendered in two cells.  However, since
private use area symbols all have their width set to one in the unicode
standard, |kitty| renders them either smaller or truncated. The exception is if
these characters are followed by a space or empty cell in which case kitty
makes use of the extra cell to render them in two cells.


Using a color theme with a background color does not work well in vim?
-----------------------------------------------------------------------

First make sure you have not changed the TERM environment variable, it should
be ``xterm-kitty``. vim uses *background color erase* even if the terminfo file
does not contain the ``bce`` capability. This is a bug in vim. You can work around
it by adding the following to your vimrc::

    let &t_ut=''

See :ref:`here <ext_styles>` for why |kitty| does not support background color erase.


I get errors about the terminal being unknown or opening the terminal failing when SSHing into a different computer?
-----------------------------------------------------------------------------------------------------------------------

This happens because the |kitty| terminfo files are not available on the server.
You can ssh in using the following command which will automatically copy the
terminfo files to the server::

    kitty +kitten ssh myserver

This ssh kitten takes all the same command line arguments
as ssh, you can alias it to ssh in your shell's rc files to avoid having to
type it each time::

    alias ssh="kitty +kitten ssh"

If for some reason that does not work (typically because the server is using a
non POSIX compliant shell), you can try using it with python instead::

    kitty +kitten ssh use-python myserver

If that also fails, perhaps because python is not installed on the remote
server, use the following one-liner instead (it
is slower as it needs to ssh into the server twice, but will work with most
servers)::

    infocmp xterm-kitty | ssh myserver tic -x -o \~/.terminfo /dev/stdin

If you are behind a proxy (like Balabit) that prevents this, you must redirect the
1st command to a file, copy that to the server and run ``tic`` manually.  If you
connect to a server, embedded or Android system that doesn't have ``tic``, copy over
your local file terminfo to the other system as :file:`~/.terminfo/x/xterm-kitty`.

Really, the correct solution for this is to convince the OpenSSH maintainers to
have ssh do this automatically, if possible, when connecting to a server, so that
all terminals work transparently.

If the server is running FreeBSD, or another system that relies on termcap
rather than terminfo, you will need to convert the terminfo file on your local
machine by running (on local machine with |kitty|)::

    infocmp -C xterm-kitty

The output of this command is the termcap description, which should be appended
to :file:`/usr/share/misc/termcap` on the remote server. Then run the following
command to apply your change (on the server)::

    cap_mkdb /usr/share/misc/termcap


Keys such as arrow keys, backspace, delete, home/end, etc. do not work when using su or sudo?
-------------------------------------------------------------------------------------------------

Make sure the TERM environment variable, is ``xterm-kitty``.  And either the
TERMINFO environment variable points to a directory containing :file:`x/xterm-kitty`
or that file is under :file:`~/.terminfo/x/`.

Note that ``sudo`` might remove TERMINFO.  Then setting it at the shell prompt can
be too late, because command line editing may not be reinitialized.  In that case
you can either ask ``sudo`` to set it or if that is not supported, insert an ``env``
command before starting the shell, or, if not possible, after sudo start another
Shell providing the right terminfo path::

    sudo … TERMINFO=$HOME/.terminfo bash -i
    sudo … env TERMINFO=$HOME/.terminfo bash -i
    TERMINFO=/home/ORIGINALUSER/.terminfo exec bash -i

You can configure sudo to preserve TERMINFO by running ``sudo
visudo`` and adding the following line::

    Defaults env_keep += "TERM TERMINFO"

If you have double width characters in your prompt, you may also need to
explicitly set a UTF-8 locale, like::

    export LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8


How do I change the colors in a running kitty instance?
------------------------------------------------------------

You can either use the
`OSC terminal escape codes <https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-Operating-System-Commands>`_
to set colors or you can define keyboard shortcuts to set colors, for example::

    map f1 set_colors --configured /path/to/some/config/file/colors.conf

Or you can enable :doc:`remote control <remote-control>` for |kitty| and use :ref:`at_set-colors`.
The shortcut mapping technique has the same syntax as the remote control
command, for details, see :ref:`at_set-colors`.

A list of pre-made color themes for kitty is available at:
`kitty-themes <https://github.com/dexpota/kitty-themes>`_

Examples of using OSC escape codes to set colors::

    Change the default foreground color:
    printf '\x1b]10;#ff0000\x1b\\'
    Change the default background color:
    printf '\x1b]11;blue\x1b\\'
    Change the cursor color:
    printf '\x1b]12;blue\x1b\\'
    Change the selection background color:
    printf '\x1b]17;blue\x1b\\'
    Change the selection foreground color:
    printf '\x1b]19;blue\x1b\\'
    Change the nth color (0 - 255):
    printf '\x1b]4;n;green\x1b\\'

You can use various syntaxes/names for color specifications in the above
examples. See `XParseColor <https://linux.die.net/man/3/xparsecolor>`_
for full details.

If a ``?`` is given rather than a color specification, kitty will respond
with the current value for the specified color.


How do I specify command line options for kitty on macOS?
---------------------------------------------------------------

Apple does not want you to use command line options with GUI applications. To
workaround that limitation, |kitty| will read command line options from the file
:file:`<kitty config dir>/macos-launch-services-cmdline` when it is launched
from the GUI, i.e. by clicking the |kitty| application icon or using ``open -a kitty``.
Note that this file is *only read* when running via the GUI.

You can, of course, also run |kitty| from a terminal with command line options, using:
:file:`/Applications/kitty.app/Contents/MacOS/kitty`.

And within |kitty| itself, you can always run |kitty| using just `kitty` as it
cleverly adds itself to the ``PATH``.


kitty is not able to use my favorite font?
---------------------------------------------

|kitty| achieves its stellar performance by caching alpha masks of each rendered
character on the GPU, so that every character needs to be rendered only once.
This means it is a strictly character cell based display.  As such it can use
only monospace fonts, since every cell in the grid has to be the same size.
Furthermore, it needs fonts to be freely resizable, so it does not support
bitmapped fonts.

If your font is not listed in ``kitty list-fonts`` it means that it is not
monospace or is a bitmapped font. On Linux you can list all monospace fonts with::

    fc-list : family spacing outline scalable | grep -e spacing=100 -e spacing=90 | grep -e outline=True | grep -e scalable=True

Note that the spacing property is calculated by fontconfig based on actual
glyph widths in the font. If for some reason fontconfig concludes your favorite
monospace font does not have ``spacing=100`` you can override it by using the
following :file:`~/.config/fontconfig/fonts.conf`::

    <?xml version="1.0"?>
    <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
    <fontconfig>
    <match target="scan">
        <test name="family">
            <string>Your Font Family Name</string>
        </test>
        <edit name="spacing">
            <int>100</int>
        </edit>
    </match>
    </fontconfig>

After creating (or modifying) this file, you may need to run the following
command to rebuild your fontconfig cache::

    fc-cache -r

Then, the font will be available in ``kitty list-fonts``.


How can I assign a single global shortcut to bring up the kitty terminal?
-----------------------------------------------------------------------------

Bringing up applications on a single key press is the job of the window
manager/desktop environment. For ways to do it with kitty (or indeed any
terminal) in different environments,
see `here <https://github.com/kovidgoyal/kitty/issues/45>`_.


How do I map key presses in kitty to different keys in the terminal program?
--------------------------------------------------------------------------------------

This is accomplished by using ``map`` with :sc:`send_text <send_text>` in :file:`kitty.conf`.
For example::

    map alt+s send_text all \x13

This maps :kbd:`alt+s` to :kbd:`ctrl+s`. To figure out what bytes to use for
the :sc:`send_text <send_text>` you can use the ``show_key`` kitten. Run::

    kitty +kitten show_key

Then press the key you want to emulate.

How do I open a new window or tab with the same working directory as the current window?
--------------------------------------------------------------------------------------------

In :file:`kitty.conf` add the following::

    map f1 launch --cwd=current
    map f2  launch --cwd=current --type=tab

Pressing :kbd:`F1` will open a new kitty window with the same working directory
as the current window. The :doc:`launch command <launch>` is very powerful,
explore :doc:`its documentation <launch>`.


Things behave differently when running kitty from system launcher vs. from another terminal?
-----------------------------------------------------------------------------------------------

This will be because of environment variables. When you run kitty from the
system launcher, it gets a default set of system environment variables. When
you run kitty from another terminal, you are actually running it from a shell,
and the shell's rc files will have setup a whole different set of environment
variables which kitty will now inherit.

You need to make sure that the environment variables you define in your shell's
rc files are either also defined system wide or via the :opt:`env` directive in
:file:`kitty.conf`. Common environment variables that cause issues are those
related to localization, such as ``LANG, LC_*`` and loading of configuration
files such as ``XDG_*, KITTY_CONFIG_DIRECTORY``.

To see the environment variables that kitty sees, you can add the following
mapping to :file:`kitty.conf`::

    map f1 show_kitty_env_vars

then pressing :kbd:`F1` will show you the environment variables kitty sees.

This problem is most common on macOS, as Apple makes it exceedingly difficult to
setup environment variables system-wide, so people end up putting them in all
sorts of places where they may or may not work.


I am using tmux and have a problem
--------------------------------------

First, terminal multiplexers are `a bad idea
<https://github.com/kovidgoyal/kitty/issues/391#issuecomment-638320745>`_, do
not use them, if at all possible. kitty contains features that do all of what
tmux does, but better, with the exception of remote persistence (:iss:`391`).
If you still want to use tmux, read on.

Image display will not work, see `tmux issue
<https://github.com/tmux/tmux/issues/1391>`_.

If you are using tmux with multiple terminals or you start it under one
terminal and then switch to another and these terminals have different TERM
variables, tmux will break. You will need to restart it as tmux does not
support multiple terminfo definitions.

Copying to clipboard via OSC 52 will not work, because tmux does not support
the extended version of that protocol, you will need to add ``no-append`` to
:opt:`clipboard_control` in kitty.conf.

If you use any of the advanced features that kitty has innovated, such as
styled underlines, desktop notifications, extended keyboard support, etc.
they may or may not work, depending on the whims of tmux's maintainer, your
version of tmux, etc.


I opened and closed a lot of windows/tabs and top shows kitty's memory usage is very high?
-------------------------------------------------------------------------------------------

``top`` is not a good way to measure process memory usage. That is because on
modern systems, when allocating memory to a process, the C library functions
will typically allocate memory in large blocks, and give the process chunks of
these blocks. When the process frees a chunk, the C library will not
necessarily release the underlying block back to the OS. So even though the
application has released the memory, ``top`` will still claim the process is
using it.

To check for memory leaks, instead use a tool like ``valgrind``. Run::

    PYTHONMALLOC=malloc valgrind --tool=massif kitty

Now open lots of tabs/windows, generate lots of output using tools like find/yes
etc. Then close all but one window. Do some random work for a few seconds in
that window, maybe run yes or find again. Then quit kitty and run::

    massif-visualizer massif.out.*

You will see the allocations graph goes up when you opened the windows, then
goes back down when you closed them, indicating there were no memory leaks.

For those interested, you can get a similar profile out of ``valgrind`` as you get
with ``top`` by adding ``--pages-as-heap=yes`` then you will see that memory
allocated in malloc is not freed in free. This can be further refined if you
use `glibc`` as your C library by setting the environment variable
``MALLOC_MMAP_THRESHOLD_=64``. This will cause free to actually free memory
allocated in sizes of more than 64 bytes. With this set, memory usage will
climb high, then fall when closing windows, but not fall all the way back. The
remaining used memory can be investigated using valgrind again, and it will
come from arenas in the GPU drivers and the per thread arenas glibc's malloc
maintains. These too allocate memory in large blocks and dont release it back
to the OS immediately.