# Frequently Asked Questions

Contents

- Frequently Asked Questions
  - Some special symbols are rendered small/truncated in kitty?
  - How do I build kitty.app on macOS?
  - Using a color theme with a background color does not work well in vim?
  - I get errors about the terminal being unknown or opening the terminal failing when SSHing into a different computer?
  - How do I change the colors in a running kitty instance?
  - How do I specify command line options for kitty on macOS?
  - kitty is not able to use my favorite font?

## 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.

## How do I build kitty.app on macOS?

Install imagemagick, optipng and librsvg using brew or similar (needed for the logo generation step). And run:

    make app

This `kitty.app` unlike the released one does not include its own copy of python and the other dependencies. So if you ever un-install/upgrade those dependencies you might have to rebuild the app.

Note that the released `kitty.dmg` includes all dependencies, unlike the `kitty.app` built above and is built automatically by using the `kitty` branch of build-calibre however, that is designed to run on Linux and is not for the faint of heart.

## 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 here 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

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

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

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

You can either use the OSC terminal escape codes to set colors or you can enable remote control for kitty and use kitty @ set-colors.

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

    fc-list : family spacing | grep spacing=100