fn sync_content_state(ui: &LibraryWindowUi)Expand description
Sync the visibility of the grid, loading, empty, and error page widgets.
The lock on library_state is released before calling
set_visible_child_name because that GTK call triggers widget
realization, factory binds, and signal handlers that may need to
re-acquire the same lock. Holding it across the call caused a
parking_lot deadlock on first library open.