Vassago

Eye comfort for GNOME that actually looks at the room.

Your webcam becomes a light sensor; your screen follows the light.
Blackout curtains at noon? Vassago sees it, and warms and dims the screen.

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Vassago, third spirit of the Goetia, is said to see what is hidden and what is yet to come. This one only sees how bright your room is, but it is very good at it.

✨ What it does

• 🌡️ Colour temperature that follows the room. Neutral 6500 K in daylight, warm in a dark room. Applied through GNOME Night Light as a hardware gamma ramp: no compositor effects and no frame cost.
• 🔆 Real monitor brightness over DDC/CI. Each monitor gets its own range, learned from the brightness you had when you first ran it.
• 👁️ Webcam as an ambient light sensor. A short burst of tiny frames every couple of minutes at a fixed, auto-ranged exposure. Nothing is stored or sent anywhere.
• 🎛️ Native Quick Settings tile. The Vassago tile takes the Night Light slot, with warmth and brightness sliders, a per-monitor readout, Pause and Measure now.
• ⚙️ libadwaita preferences with one-tap calibration for your own room.
• 🤝 Plays nice. If a video call is using the camera, the measurement is skipped and the call is never touched.
• ⏸️ Pause vs. off. Pause stops measuring but keeps the current colour and brightness, which is handy for a call or a film. It clears itself at the next login. Turning the tile off restores your own Night Light settings and monitor brightness.

🧭 How it works

flowchart LR
    cam["📷 Webcam<br/>(manual exposure burst)"] --> d["vassagod<br/>meter → smooth → map"]
    d -->|"Night Light temperature<br/>(GSettings)"| gsd["gnome-settings-daemon<br/>gamma ramp"]
    d -->|"VCP 0x10 brightness<br/>(ddcutil)"| mon["🖥️ Monitors"]
    d <-->|"D-Bus<br/>io.github.fureunoir.Vassago"| ext["GNOME Shell extension<br/>Quick Settings + prefs"]

1. Metering. The camera is switched to manual exposure with zero gain, then ffmpeg grabs 8 frames at 160×120 and the camera's own settings are put back. The reading is log2(mean luminance / exposure). Exposure auto-ranges so frames are neither black nor clipped, which gives a stable figure from a pitch-dark room to a sunny one.
2. Mapping. The reading is placed between your dark and bright calibration points to get a 0–1 room level, smoothed so a passing shadow does nothing. The level is applied only when it moves by more than 5 %.
3. Applying. Temperature goes from warm to neutral along a gentle curve. Brightness goes from each monitor's min to max, plus your correction, and is stepped smoothly instead of jumping.

📦 Requirements

Desktop	GNOME Shell 50 or 51 (Wayland or X11)
Packages	python3-gobject, ffmpeg, ddcutil
Camera	any UVC webcam with manual exposure (tested: Logitech C922)
Monitors	DDC/CI enabled in the OSD (optional: without it you get colour only)
Kernel	i2c-dev loaded, with user access to the GPU's I²C buses

On Fedora:

sudo dnf install python3-gobject ffmpeg ddcutil
echo i2c-dev | sudo tee /etc/modules-load.d/i2c-dev.conf
sudo modprobe i2c-dev
ddcutil detect        # your monitors should show up here

Warning

OpenRGB users: openrgb-udev-rules gives your user access to every I²C bus, including the motherboard SMBus. On some boards, probing that bus hangs the machine. ddcutil only needs the GPU buses, so you can drop OpenRGB's I²C rule (USB lighting keeps working):

sed 's/^KERNEL=="i2c-\[0-99\]\*", TAG+="uaccess"/# &/' \
    /usr/lib/udev/rules.d/60-openrgb.rules | sudo tee /etc/udev/rules.d/60-openrgb.rules

🚀 Install

git clone https://git.wiseless.net/fureunoir/Vassago.git
cd Vassago
./install.sh

Everything is installed for your user only, with no root:

What	Where
daemon	~/.local/bin/vassagod
extension	~/.local/share/gnome-shell/extensions/vassago@fureunoir/
systemd user unit	~/.config/systemd/user/vassagod.service
D-Bus activation	~/.local/share/dbus-1/services/io.github.fureunoir.Vassago.service

On Wayland, log out and back in once so GNOME Shell loads the new extension.

🎯 Calibrate (2 minutes, once)

Open Quick Settings → Vassago → Vassago Settings → Calibration:

1. Make the room as dark as it usually gets (curtains closed, lamps off). Press Measure, then Save as dark.
2. Make it as bright as it usually gets. Press Measure, then Save as bright.

Then set how warm the screen gets in the dark, and each monitor's brightness range under Brightness.

🔧 Configuration

All settings live in GSettings (org.gnome.shell.extensions.vassago) and apply live:

Key	Default	Meaning
enabled	true	master switch (the Quick Settings toggle)
paused	false	stop measuring, keep current values; cleared at daemon start
interval	120	seconds between camera readings
camera-device	/dev/video0	which webcam to use
temperature-neutral	6500	K in a bright room
temperature-warm	4500	K in a dark room
brightness-enabled	true	drive monitor brightness over DDC/CI
brightness-offset	0	correction in percentage points, −50…+50
ambient-dark / ambient-bright	4.0 / 10.0	calibration points
monitor-limits	learned	per-monitor (min, max) brightness

From a terminal:

export GSETTINGS_SCHEMA_DIR=~/.local/share/gnome-shell/extensions/vassago@fureunoir/schemas
gsettings set org.gnome.shell.extensions.vassago temperature-warm 4000

🛰️ D-Bus API

io.github.fureunoir.Vassago at /io/github/fureunoir/Vassago:

Member
State (property, s)	JSON: status, last reading, room level, temperature, monitors
MeasureNow()	take a reading right away
Calibrate(s point)	store the last reading as "dark" or "bright"

busctl --user get-property io.github.fureunoir.Vassago \
    /io/github/fureunoir/Vassago io.github.fureunoir.Vassago State

🩺 Troubleshooting

Symptom	Try
Tile says Daemon not running	journalctl --user -u vassagod -f
No monitors in the tile	ddcutil detect; turn on DDC/CI in the monitor's OSD
Camera LED blinks too often	raise interval, or Pause for a while
Screen too yellow in the dark	raise Warmth in the dark toward 6500 K
Dims too much in a dim room	the camera also sees the screen's own glow; save a new dark point with the screen at the brightness you like

🧹 Uninstall

Turn the tile off first: that restores your Night Light settings and monitor brightness. Then:

systemctl --user disable --now vassagod.service
gnome-extensions disable vassago@fureunoir
rm -r ~/.local/share/gnome-shell/extensions/vassago@fureunoir \
      ~/.local/bin/vassagod \
      ~/.config/systemd/user/vassagod.service \
      ~/.local/share/dbus-1/services/io.github.fureunoir.Vassago.service

📜 License

MIT © 2026 Egor Gorbunov