The Content Area
The content area is the total area occuppied by the content of an overflowing box
(see overflowBehavior in Positioning Elements), of which
only the portion inside the viewport is visible at a time.
The read-only properties contentWidth and contentHeight tell the current
total size of the content area.
The Viewport
The properties contentX, contentY specify the current top-left position of the
scrolling viewport inside a box.
You may modify these properties to scroll manually. Otherwise, they are updated automatically as the user scrolls.
The size of the viewport is described by the read-only bboxWidth and bboxHeight properties, since it is the
same as the element's size.
Scrollbars
The boolean scrollbars property of Box controls if the HTML runtime
environment shall provide native scrollbars automatically. The default value is false,
which means that no native scrollbars are shown. The element ui.ScrollIndicator
provides an alternative to native scrollbars for a uniform look and feel across all
platforms.