Function apply_theme_class_to_root 

pub fn apply_theme_class_to_root(
    theme: Res<'_, StyleManager>,
    store: Option<ResMut<'_, PropertyStore>>,
    roots: Query<'_, '_, &mut LumenClasses, Without<ChildOf>>,
)

👎Deprecated:

Use style_manager_to_signal + apply_theme_signal_to_root_classes instead. The split removes the joint Res<StyleManager> / ResMut<Signals> / Query<&mut LumenClasses> borrow and replaces the &mut *classes reborrow trick with notify-queue gating.

Legacy theme application path - superseded by the W1.6 split of style_manager_to_signal (producer) + apply_theme_signal_to_root_classes (consumer). Retained as a #[deprecated] thin wrapper so external callers that explicitly registered this system keep compiling; new registrations should use the split pair instead.