Actually the example I gave was not the best since this can easily be
achieved with a background image set in the sway config, and
window { background-color: transparent; }

But I think this patch could still be useful for other customisations.

---
Small patch that allows different CSS styling to be applied to each
monitor on a multi-head system. e.g:

window#DP-1 { background-image: url("image.tiff"); }
window#DP-2 { background-image: url("image2.tiff"); }

Code taken from jovanlanik/gtklock on Github

(This is my first time using the email-patch workflow, aplologies if it
is formatted incorrectly)

 gtkgreet/window.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
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