To the end user, VScroll presents one continuous scrollable list. It maintains an ordered buffer of items; the consumer—an application or framework integration—renders a DOM row for each. Dataset positions outside the buffer remain virtual, represented by empty space.
The dark-blue region shows rows visible through the viewport, whose height settings.padding targets each outlet's size as a fraction of 0.5); an outlet may be shorter near a dataset boundary.
The white regions represent virtual rows. Empty padding elements before and after the buffer reserve their estimated space. Unlike outlets, these elements contain no rendered rows. See Rendering for the DOM structure.
The items in this buffer originate with the datasource supplied to Workflow: it returns application values for requested index ranges. VScroll wraps each value in an item: item.data holds the value, while item.$index is its current dataset position—the number shown in the diagrams.
The consumer supplies run(items) when constructing Workflow. During initialization and after buffer changes, VScroll calls it with the complete current item buffer, not just newly fetched items. The consumer uses this list to keep the corresponding DOM rows in sync. See Rendering for the implementation contract.
As the user scrolls, VScroll requests data for approaching positions, adds the resulting items to the buffer, clips distant items, and adjusts the padding elements. It measures rendered rows to refine its estimates of virtual space and may correct the scroll position to keep content in place. Setting settings.infinite = true switches the scroller from virtual scrolling to infinite scrolling: automatic clipping stops and loaded rows accumulate. The dataset itself may still be finite.