Learning_GTK4_tree/testsuite/reftests/gtk-image-effect-inherit.css

GtkBox > :nth-child(1) {
  -gtk-icon-filter: none;
}

GtkBox > :nth-child(2) {
  -gtk-icon-filter: brightness(1.2);
}

GtkBox > :nth-child(3) {
  -gtk-icon-filter: opacity(0.5);
}