Wlinfo queries Wayland for information about physical displays connected to the system. It can print information about the physical dimensions of such displays, and screen resolution, and display scaling characteristics.

Wlinfo is built as a standard automake/autoconf program:

$ ./autogen.sh
$ ./configure
$ make

The output of wlinfo looks like this:

output 4
---------
x: 0
y: 0
physical_width: 640
physical_height: 400
subpixel: 0
make: DEL
model: DELL U3014
width: 2560
height: 1600
dpi: 103.2
scale: 1

output 5
---------
x: 2560
y: 0
physical_width: 310
physical_height: 170
subpixel: 0
make: MEI
model: 0x96a2
width: 2560
height: 1440
dpi: 451.3
scale: 2

My personal motivation for this code is to allow Emacs instances to pick an appropriate font size. This is necessary because I have a high-DPI laptop screen, and a low-DPI monitor that I sometimes attach to my laptop. Wayland itself supports per-monitor display scaling, so it can scale the high-DPI monitor at 2x (for instance), and the low-DPI monitor at 1x. However, Emacs is a legacy X11 application that can't do display scaling. Therefore I need my Emacs instance to choose an appropriate font size based on which physical displays are actually connected to the system at the time that Emacs starts up.

This code is released under a version of the MIT license used by X11. This is the same license used by Wayland and Weston. Some of this code is derived from code found in Weston (in particular, the code for weston-info).