fcitx5-commit

A tiny fcitx5 addon that lets other programs insert a UTF-8 string into the currently focused text field over D-Bus.

fcitx5 has no external API for that: its Controller1 D-Bus interface can switch input methods, but it cannot type text. Programs that want to insert text are left with synthesizing key presses (uinput, wtype, ydotool, …), which is slow, depends on the active keyboard layout and cannot produce characters the layout does not have. This addon commits the string straight into the focused input context — the same path fcitx5 uses when you pick a pinyin candidate — so any text arrives in one piece, whatever the layout.

It is used by skvirt, an on-screen keyboard for KDE Plasma / KWin, to type dictated text (voice input); skvirt falls back to key taps when the addon is not installed.

D-Bus API

The object lives on fcitx5's own session-bus connection, so it is reached through fcitx5's well-known name:

Service	org.fcitx.Fcitx5
Object path	/commit
Interface	io.github.vendetta1871.Commit1
Method	CommitString(s text) → (b committed)

CommitString looks at the most recent input context:

• if there is none, or it does not have focus, nothing is committed and the method returns false;
• otherwise text is committed (when it is non-empty) and the method returns true.

So an empty string is a harmless probe for "is there a focused text field to type into?".

# Type "Hello, мир ✓" into whatever text field has focus right now
busctl --user call org.fcitx.Fcitx5 /commit io.github.vendetta1871.Commit1 CommitString s "Hello, мир ✓"

# Probe: prints "b true" if a text field has focus, "b false" otherwise
busctl --user call org.fcitx.Fcitx5 /commit io.github.vendetta1871.Commit1 CommitString s ""

# Is the addon loaded at all?
busctl --user introspect org.fcitx.Fcitx5 /commit

The same call with gdbus:

gdbus call --session --dest org.fcitx.Fcitx5 --object-path /commit \
    --method io.github.vendetta1871.Commit1.CommitString "text"

Install

Arch Linux (AUR)

paru -S fcitx5-commit-git      # or any other AUR helper

From source

Requires fcitx5 ≥ 5.1 (with its development headers — part of the fcitx5 package on Arch), CMake and a C++20 compiler.

git clone https://github.com/Vendetta1871/fcitx5-commit.git
cd fcitx5-commit
cmake -B build -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr
cmake --build build
sudo cmake --install build

With CMAKE_INSTALL_PREFIX equal to fcitx5's own prefix the files go where fcitx5 looks for addons:

• /usr/lib/fcitx5/libcommit.so
• /usr/share/fcitx5/addon/commit.conf

Restart fcitx5

fcitx5 only discovers addons at startup, so restart fcitx5 after installing. Usually fcitx5 -r -d does it. On KDE Plasma Wayland KWin starts fcitx5 itself (as the virtual keyboard), so instead re-select fcitx5 in System Settings → Keyboard → Virtual Keyboard, or log out and back in.

The addon is enabled by default and loads together with fcitx5 (it is not loaded on demand); it shows up in fcitx5's addon list as "Commit String over D-Bus".

To see what it does, run fcitx5 with --verbose=commit=5.

Security

Any process that can talk to your session bus can call CommitString and insert text into whichever field has focus. This is the same trust boundary as fcitx5's own org.fcitx.Fcitx.Controller1 D-Bus API (which can, for example, switch your input method) and as the session bus in general: programs running as you on your session are trusted. The addon only ever commits text; it cannot read what you type, and it never sees key events.

License

GPL-3.0-or-later