How is the icon theme determined?

[github-usr-name]

My GTK (v3 & v4) configurations specify that the Adwaita icon theme should be used by default. However, the --custom-icon option appears to be using the hicolor theme only and is not displaying the themed icons.

Machine configuration:

❯ cat ~config/gtk-3.0/settings.ini
[Settings]
gtk-theme-name=adw-gtk3-dark
gtk-icon-theme-name=Adwaita
# additional settings elided 
❯ cat ~config/gtk-4.0/settings.ini
[Settings]
gtk-theme-name=Adwaita:dark
gtk-icon-theme-name=Adwaita

Is there a mechanism to inform swayosd that the Adwaita theme should be used instead of the default hicolor theme?

[ErikReider]

What's the output of this command?: gsettings get org.gnome.desktop.interface icon-theme