GTK+ is known for not picking up some variables from ${XDG_CONFIG_HOME}/gtk-3.0/settings.ini, most notably themes.
This happens because when GTK+ uses the wayland backend, a subset of variables are pulled from the gsettings schema org.gnome.desktop.interface, whereas on X11 GTK talks to a XSETTINGS daemon that usually does this for you, or when missing, falls back to the user's setting.ini file.
This only applies for settings that belong to org.gnome.desktop.interface. Some settings, like gtk-application-prefer-dark-theme, are still read from your settings.ini.
Cursor themes can be set in GTK for now, but a better solution is to let sway handle it for you. Support for the cursor shape protocol has been merged and is in sway 1.9. You also need clients to use the protocol (which usually depends on their toolkit library version).
Workarounds
Setting GTK_THEME
If you only care about your GTK theme, you can export the GTK_THEME environment variable before running your GTK programs. While this is quite simple, it's also fairly limited, since there are no environment variables to set other settings, like icon/cursor themes.
This also may cause issues with applications reading the theme from GtkSettings as this is a development environment variable and does not change that value.
Setting values in gsettings
The proper workaround is to call gsettings set org.gnome.desktop.interface <key> <value> yourself at any point before starting any GTK program, for each setting that you want set. A good place to do so is either your shell's rc files, or using exec in your sway config.
You can list valid keys for the schema using gsettings list-keys org.gnome.desktop.interface; you most notably want to set gtk-theme, cursor-theme and icon-theme:
set $gnome-schema org.gnome.desktop.interface
exec_always {
gsettings set $gnome-schema gtk-theme 'Your theme'
gsettings set $gnome-schema icon-theme 'Your icon theme'
gsettings set $gnome-schema cursor-theme 'Your cursor Theme'
gsettings set $gnome-schema font-name 'Your font name'
}
If you'd rather have those values picked from your settings.ini file, here is a small convenient script to do just that:
#!/bin/sh
# usage: import-gsettings
config="${XDG_CONFIG_HOME:-$HOME/.config}/gtk-3.0/settings.ini"
if [ ! -f "$config" ]; then exit 1; fi
gnome_schema="org.gnome.desktop.interface"
gtk_theme="$(grep 'gtk-theme-name' "$config" | sed 's/.*\s*=\s*//')"
icon_theme="$(grep 'gtk-icon-theme-name' "$config" | sed 's/.*\s*=\s*//')"
cursor_theme="$(grep 'gtk-cursor-theme-name' "$config" | sed 's/.*\s*=\s*//')"
font_name="$(grep 'gtk-font-name' "$config" | sed 's/.*\s*=\s*//')"
gsettings set "$gnome_schema" gtk-theme "$gtk_theme"
gsettings set "$gnome_schema" icon-theme "$icon_theme"
gsettings set "$gnome_schema" cursor-theme "$cursor_theme"
gsettings set "$gnome_schema" font-name "$font_name"
Importing the gtk, icon, and cursor themes:
exec_always import-gsettings
Removing the rounded corners and dropshadow of themes like Adwaita
If you use 1 pixel border the theme's shadow can leak underneath, also sway's border can only be without border radius so to remove any of these issues make a file at ${XDG_CONFIG_HOME}/gtk-3.0/gtk.css put following selectors there.
/** Some apps use titlebar class and some window */
.titlebar,
window {
border-radius: 0;
box-shadow: none;
}
/** also remove shadows */
decoration {
box-shadow: none;
}
decoration:backdrop {
box-shadow: none;
}
XSettings
Some GTK applications running via XWayland, and some Java applications, need an XSettings daemon running in order to pick up the themes and font settings.
One implementation is xsettingsd.
Gnome (or rather, the Gnome Settings Daemon) provides its own XSettings daemon, usually installed at /usr/lib/xsettings.
