ListItemFactory
A GtkListItemFactory creates widgets for the items taken from a GListModel.
This is one of the core concepts of handling list widgets such as class@Gtk.ListView or class@Gtk.GridView.
The GtkListItemFactory is tasked with creating widgets for items taken from the model when the views need them and updating them as the items displayed by the view change.
A view is usually only able to display anything after both a factory and a model have been set on the view. So it is important that you do not skip this step when setting up your first view.
Because views do not display the whole list at once but only a few items, they only need to maintain a few widgets at a time. They will instruct the GtkListItemFactory to create these widgets and bind them to the items that are currently displayed.
As the list model changes or the user scrolls to the list, the items will change and the view will instruct the factory to bind the widgets to those new items.
The actual widgets used for displaying those widgets is provided by you.
When the factory needs widgets created, it will create a GtkListItem and hand it to your code to set up a widget for. This list item will provide various properties with information about what item to display and provide you with some opportunities to configure its behavior. See the class@Gtk.ListItem documentation for further details.
Various implementations of GtkListItemFactory exist to allow you different ways to provide those widgets. The most common implementations are class@Gtk.BuilderListItemFactory which takes a GtkBuilder .ui file and then creates widgets and manages everything automatically from the information in that file and class@Gtk.SignalListItemFactory which allows you to connect to signals with your own code and retain full control over how the widgets are setup and managed.
A GtkListItemFactory is supposed to be final - that means its behavior should not change and the first widget created from it should behave the same way as the last widget created from it. If you intend to do changes to the behavior, it is recommended that you create a new GtkListItemFactory which will allow the views to recreate its widgets.
Once you have chosen your factory and created it, you need to set it on the view widget you want to use it with, such as via method@Gtk.ListView.set_factory. Reusing factories across different views is allowed, but very uncommon.