Wayland Display Info

wayland-display-info is a lightweight user daemon that monitors your Wayland compositor through the wlr-output-management protocol and keeps the file

/var/cache/wayland-display-info/display-info

up-to-date. Each line describes a connected output in the form

<OUTPUT_NAME> <DPI> <WIDTH_PX> <HEIGHT_PX>

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How DPI is computed

• Letter-/Pillar-boxing aware – when the selected mode’s aspect ratio differs from the panel’s native ratio and the compositor inserts black bars, the daemon reports the larger of the horizontal or vertical DPI.
  This keeps the figure constant for the axis that is fully utilised, so the value always reflects the density of the visible image.
• Rotation neutral – a panel rotated by 90 ° or 270 ° still shows the same number of pixels on the same physical surface; therefore rotation has no effect on pixel density and requires no special handling.

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🚀 Installation

Arch Linux (AUR)

pikaur -S wayland-display-info

The PKGBUILD installs

• the binary in /usr/lib/wayland-display-info/
• the user service wayland-display-info.service
• a tmpfiles entry that creates /var/cache/wayland-display-info at boot (mode 1777)

After installation the service is enabled automatically; log out and back in, or start it straight away:

systemctl --user start wayland-display-info.service

From source

git clone https://github.com/acrion/wayland-display-info
cd wayland-display-info
./generate-protocol-stubs.sh
./build.sh
sudo ./install.sh

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🔎 Status and diagnostics

systemctl --user status wayland-display-info.service
cat /var/cache/wayland-display-info/display-info