chromium-wayland-cedilla-fix

Make ' + c produce ç (and ' + C produce Ç) in Chromium on native Wayland — without an input method framework (no fcitx5, no ibus), keeping the native Wayland backend.

Targeted at Arch Linux / Arch Linux ARM + Wayland compositors (Hyprland, Sway, river, …) using the US-International layout, but the technique works anywhere.

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The problem

On the US-International layout, ' is a dead key (dead_acute). Pressing ' + c should be configurable to produce the cedilla ç, and on most apps it is — via ~/.XCompose / the system Compose table.

But Chromium on native Wayland ignores ~/.XCompose and XCOMPOSEFILE entirely. Instead of libxkbcommon, it uses ChromeOS' ui::CharacterComposer with a compose table compiled into the binary. That table hardcodes dead_acute + c → ć (LATIN SMALL LETTER C WITH ACUTE, U+0107), so Portuguese / French / Catalan / Turkish users get ć instead of ç.

This is a known, still-open Chromium bug: crbug 40272818 — Custom compose key sequences (.XCompose) do not work on Chrome + Wayland.

The usual "solutions" each cost you something:

Workaround	Keeps '+c→ç	Native Wayland	No IME
Run Chromium under X11 (--ozone-platform=x11)	✅	❌	✅
fcitx5 / ibus + --enable-wayland-ime	✅	✅	❌
This patch	✅	✅	✅

How it works

The hardcoded compose table stores entries as [input uint16 LE][output uint16 LE]. The acute-accent row looks like a→á, c→ć, e→é, …. We change only the output of c/C:

c (0x0063) -> ć (0x0107):   63 00 07 01   =>   63 00 e7 00   (ç U+00E7)
C (0x0043) -> Ć (0x0106):   43 00 06 01   =>   43 00 c7 00   (Ç U+00C7)

The patch matches by byte pattern, not by offset, so it keeps working across Chromium releases (3 copies of the table exist in the binary; all are patched). Nothing else is touched — every other accent ('+a→á, '+e→é, …) is unchanged.

Heads up: after this, you can no longer type ć/Ć via ' + c in Chromium. If you need those, type them another way.

Install (Arch / Arch Linux ARM)

git clone https://github.com/lcassa/chromium-wayland-cedilla-fix.git
cd chromium-wayland-cedilla-fix
sudo ./install.sh

This:

1. installs chromium-cedilla-patch.py to /usr/local/bin/,
2. installs a pacman hook (/etc/pacman.d/hooks/) that re-applies the patch automatically after every chromium upgrade,
3. applies the patch once.

Then restart Chromium completely and test ' + c → ç.

If your Chromium binary is not at /usr/lib/chromium/chromium, pass the path:

sudo ./install.sh /path/to/chromium

Uninstall

sudo ./uninstall.sh

Restores the pristine binary from the .orig backup and removes the hook/script.

Caveats (please read)

• This patches a system binary. It is unofficial. A pristine .orig backup is made before the first patch, and a timestamped .bak-* on every run.
• If a future Chromium version changes the compose-table layout, the pattern won't match — the script then does nothing and warns (it never corrupts the binary). If that happens, please open an issue.
• The pacman hook keeps it applied across upgrades; if you install Chromium via Flatpak/Snap instead, you'll need to adapt the path and re-apply mechanism.

License

MIT — see LICENSE.