Lazy-loading of smartview
render_contact_photo & set_tree_model should be async as it takes quite some times when a lot of contacts are there
cf https://blogs.gnome.org/ebassi/documentation/lazy-loading/comment-page-1/
render_contact_photo & set_tree_model should be async as it takes quite some times when a lot of contacts are there
cf https://blogs.gnome.org/ebassi/documentation/lazy-loading/comment-page-1/