A fast, lightweight and minimalistic Wayland terminal emulator
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Installing

  1. Overview
  2. Requirements
    1. Running
    2. Building
  3. Arch Linux
  4. Other
    1. Setup
    2. Options
    3. Release build
      1. Size optimized
      2. Performance optimized, non-PGO
      3. Performance optimized, PGO
        1. Partial PGO
        2. Full PGO
        3. Use the generated PGO data
      4. Profile Guided Optimization
    4. Debug build
    5. Terminfo
    6. Running the new build

Overview

foot makes use of a couple of libraries I have developed: tllist and fcft. As such, they will most likely not have been installed already. You can either install them as system libraries or build them as subprojects in foot.

When building foot, they will first be searched for as system libraries. If found, foot will link dynamically against them. If not found, meson will attempt to download and build them as subprojects.

Requirements

Running

  • fontconfig
  • freetype
  • pixman
  • wayland (client and cursor libraries)
  • xkbcommon
  • fcft 1

If you are packaging foot, you may also want to consider adding the following optional dependencies:

  • libnotify: desktop notifications by default uses notify-send.
  • xdg-utils: URLs are by default launched with xdg-open.
  • bash-completion: If you want completion for positional arguments.

Building

In addition to the dev variant of the packages above, you need:

  • meson
  • ninja
  • wayland protocols
  • ncurses (needed to generate terminfo)
  • scdoc (for man page generation, not needed if documentation is disabled)
  • llvm (for PGO builds with Clang)
  • tllist 1

A note on compilers; in general, foot runs much faster when compiled with gcc instead of clang. A profile-guided gcc build can be more than twice as fast as a clang build.

Note GCC 10.1 has a performance regression that severely affects foot when doing PGO builds and building with -O2; it is about 30-40% slower compared to GCC 9.3.

The work around is simple: make sure you build with -O3. This is the default with meson --buildtype=release, but e.g. makepkg can override it (makepkg uses -O2 by default).

Arch Linux

Install from AUR:

Or use makepkg to build the bundled PKGBUILD (run makepkg in the source root directory).

Unlike the AUR packages, the bundled PKGBUILD requires tllist and fcft to be installed as system libraries. If you do not want this, please edit the PKGBUILD file, or install manually (see Other below).

Note that it will do a profiling-guided build, and that this requires a running wayland session since it needs to run an intermediate build of foot.

Other

Foot uses meson. If you are unfamiliar with it, the official tutorial might be a good starting point.

I also recommend taking a look at the bundled Arch PKGBUILD file, to see how it builds foot. Especially so if you intend to install a release build of foot, in which case you might be interested in the compiler flags used there.

A note on terminfo; the terminfo database exposes terminal capabilities to the applications running inside the terminal. As such, it is important that the terminfo used reflects the actual terminal. Using the xterm-256color terminfo will, in many cases, work, but I still recommend using foot’s own terminfo. There are two reasons for this:

  • foot’s terminfo contains a couple of non-standard capabilities, used by e.g. tmux.
  • New capabilities added to the xterm-256color terminfo could potentially break foot.
  • There may be future additions or changes to foot’s terminfo.

As of ncurses 2021-07-31, ncurses includes a version of foot’s terminfo. The recommendation is to use those, and only install the terminfo definitions from this git repo if the system’s ncurses predates 2021-07-31.

But, note that the foot terminfo definitions in ncurses’ lack the non-standard capabilities. This mostly affects tmux; without them, terminal-overrides must be configured to enable truecolor support. For this reason, it is possible to install “our” terminfo definitions as well, either in a non-default location, or under a different name.

Both have their set of issues. When installing to a non-default location, foot will set the environment variable TERMINFO in the child process. However, there are many situations where this simply does not work. See dnkl/foot#695 for details.

Installing them under a different name generally works well, but will break applications that check if $TERM == foot.

Hence the recommendation to simply use ncurses’ terminfo definitions if available.

If packaging “our” terminfo definitions, I recommend doing that as a separate package, to allow them to be installed on remote systems without having to install foot itself.

Setup

To build, first, create a build directory, and switch to it:

mkdir -p bld/release && cd bld/release

Options

Available compile-time options:

Option Type Default Description Extra dependencies
-Ddocs feature auto Builds and install documentation scdoc
-Dime bool true Enables IME support None
-Dgrapheme-clustering feature auto Enables grapheme clustering libutf8proc
-Dterminfo feature enabled Build and install terminfo files tic (ncurses)
-Ddefault-terminfo string foot Default value of TERM none
-Dcustom-terminfo-install-location string ${datadir}/terminfo Value to set TERMINFO to None

Documentation includes the man pages, the example foot.ini, readme, changelog and license files.

-Ddefault-terminfo: I strongly recommend leaving the default value. Use this option if you plan on installing the terminfo files under a different name. Setting this changes the default value of $TERM, and the names of the terminfo files (if -Dterminfo=enabled).

-Dcustom-terminfo-install-location enables foot’s terminfo to co-exist with ncurses’ version, without changing the terminfo names. The idea is that you install foot’s terminfo to a non-standard location, for example /usr/share/foot/terminfo. Use -Dcustom-terminfo-install-location to tell foot where the terminfo is. Foot will set the environment variable TERMINFO to this value (with ${prefix} added). The value is relative to ${prefix}.

Note that there are several issues with this approach: dnkl/foot#695.

If left unset, foot will not set or modify TERMINFO.

-Dterminfo can be used to disable building the terminfo definitions in the meson build. It does not change the default value of TERM, and it does not disable TERMINFO, if -Dcustom-terminfo-install-location has been set. Use this if packaging the terminfo definitions in a separate package (and the build script isn’t shared with the ‘foot’ package).

Example:

meson --prefix=/usr -Dcustom-terminfo-install-location=lib/foot/terminfo

The above tells foot its terminfo definitions will be installed to /usr/lib/foot/terminfo. This is the value foot will set the TERMINFO environment variable to.

If -Dterminfo is enabled (the default), then the terminfo files will be built as part of the regular build process, and installed to the specified location.

Packagers may want to set -Dterminfo=disabled, and manually build and install the terminfo files instead.

Release build

Below are instructions for building foot either size optimized, performance optimized, or performance optimized using PGO.

PGO - Profile Guided Optimization - is a way to optimize a program better than -O3 can, and is done by compiling foot twice: first to generate an instrumented version which is used to run a payload that exercises the performance critical parts of foot, and then a second time to rebuild foot using the generated profiling data to guide optimization.

In addition to being faster, PGO builds also tend to be smaller than regular -O3 builds.

Size optimized

To optimize for size (i.e. produce a small binary):

export CFLAGS="$CFLAGS -Os"
meson --buildtype=release --prefix=/usr -Db_lto=true ../..
ninja
ninja test
ninja install

Performance optimized, non-PGO

To do a regular, non-PGO build optimized for performance:

export CFLAGS="$CFLAGS -O3"
meson --buildtype=release --prefix=/usr -Db_lto=true ../..
ninja
ninja test
ninja install

Use -O2 instead of -O3 if you prefer a slightly smaller (and slower!) binary.

Performance optimized, PGO

There are a lot more steps involved in a PGO build, and for this reason there are a number of helper scripts available.

pgo/pgo.sh is a standalone script that pieces together the other scripts in the pgo directory to do a complete PGO build. This script is intended to be used when doing manual builds.

Note that all “full” PGO builds (which auto will prefer, if possible) require LC_CTYPE to be set to an UTF-8 locale. This is not done automatically.

Example:

cd foot
./pgo/pgo.sh auto . /tmp/foot-pgo-build-output

(run ./pgo/pgo.sh to get help on usage)

It supports a couple of different PGO builds; partial (covered in detail below), full (also covered in detail below), and (full) headless builds using Sway or cage.

Packagers may want to use it as inspiration, but may choose to support only a specific build type; e.g. full/headless with Sway.

To do a manual PGO build, instead of using the script(s) mentioned above, detailed instructions follows:

First, configure the build directory:

export CFLAGS="$CFLAGS -O3"
meson --buildtype=release --prefix=/usr -Db_lto=true ../..

It is very important -O3 is being used here, as GCC-10.1.x and later have a regression where PGO with -O2 is much slower.

Clang users must add -Wno-ignored-optimization-argument to CFLAGS.

Then, tell meson we want to generate profiling data, and build:

meson configure -Db_pgo=generate
ninja
ninja test

Next, we need to actually generate the profiling data.

There are two ways to do this: a partial PGO build using a PGO helper binary, or a full PGO build by running the real foot binary. The latter has slightly better results (i.e. results in a faster binary), but must be run in a Wayland session.

A full PGO build also tends to be smaller than a partial build.

Partial PGO

This method uses a PGO helper binary that links against the VT parser only. It is similar to a mock test; it instantiates a dummy terminal instance and then directly calls the VT parser with stimuli.

It explicitly does not include the Wayland backend and as such, it does not require a running Wayland session. The downside is that not all code paths in foot is exercised. In particular, the rendering code is not. As a result, the final binary built using this method is slightly slower than when doing a full PGO build.

We will use the pgo binary along with input corpus generated by scripts/generate-alt-random-writes.py:

./footclient --version
./foot --version
tmp_file=$(mktemp)
../../scripts/generate-alt-random-writes \
    --rows=67 \
    --cols=135 \
    --scroll \
    --scroll-region \
    --colors-regular \
    --colors-bright \
    --colors-256 \
    --colors-rgb \
    --attr-bold \
    --attr-italic \
    --attr-underline \
    --sixel \
    ${tmp_file}
./pgo ${tmp_file} ${tmp_file} ${tmp_file}
rm ${tmp_file}

The first step, running ./foot --version and ./footclient --version might seem unnecessary, but is needed to ensure we have some profiling data for functions not covered by the PGO helper binary. Without this, the final link phase will fail.

The snippet above then creates an (empty) temporary file. Then, it runs a script that generates random escape sequences (if you cat ${tmp_file} in a terminal, you’ll see random colored characters all over the screen). Finally, we feed the randomly generated escape sequences to the PGO helper. This is what generates the profiling data used in the next step.

You are now ready to use the generated PGO data.

Full PGO

This method requires a running Wayland session.

We will use the script scripts/generate-alt-random-writes.py:

./footclient --version
foot_tmp_file=$(mktemp)
./foot --config=/dev/null --term=xterm sh -c "<path-to-generate-alt-random-writes.py> --scroll --scroll-region --colors-regular --colors-bright --colors-256 --colors-rgb --attr-bold --attr-italic --attr-underline --sixel ${foot_tmp_file} && cat ${foot_tmp_file}"
rm ${foot_tmp_file}

You should see a foot window open up, with random colored text. The window should close after ~1-2s.

The first step, ./footclient --version might seem unnecessary, but is needed to ensure we have some profiling data for footclient. Without this, the final link phase will fail.

Use the generated PGO data

Now that we have generated PGO data, we need to rebuild foot. This time telling meson (and ultimately gcc/clang) to use the PGO data.

If using Clang, now do (this requires llvm to have been installed):

llvm-profdata merge default_*profraw --output=default.profdata

Next, tell meson to use the profile data we just generated, and rebuild:

meson configure -Db_pgo=use
ninja
ninja test

Continue reading in Running the new build

Debug build

meson --buildtype=debug ../..
ninja
ninja test

Terminfo

By default, building foot also builds the terminfo files. If packaging the terminfo files in a separate package, it might be easier to simply disable the terminfo files in the regular build, and compile the terminfo files manually instead.

To build the terminfo files, run:

sed 's/@default_terminfo@/foot/g' foot.info | \
    tic -o <output-directory> -x -e foot,foot-direct -

Where ”output-directory” must match the value passed to -Dcustom-terminfo-install-location in the foot build.

To compile and install directly (assuming the default -Dcustom-terminfo-install-location):

sudo tic -o /usr/share/foot/terminfo ...

Or, if packaging:

tic -o ${DESTDIR}/usr/share/foot/terminfo ...

Running the new build

You can now run it directly from the build directory:

./foot

Or, if you did not install the terminfo definitions:

./foot --term xterm-256color

  1. can also be built as subprojects, in which case they are statically linked.