public class Viewport : Widget, Accessible, Buildable, ConstraintTarget, Scrollable
`GtkViewport` implements scrollability for widgets that lack their own scrolling capabilities.
Use `GtkViewport` to scroll child widgets such as `GtkGrid`, `GtkBox`, and so on.
The `GtkViewport` will start scrolling content only if allocated less than the child widget’s minimum size in a given orientation.
`GtkViewport` has a single CSS node with name `viewport`.
`GtkViewport` uses the gtk_accessible_role_group role.