Use case

We use @justinmc's InteractiveViewer widget for vertical lists that can have an arbitrary width (the items can have arbitrary widths).
→ you can obviously apply the same to the reverse dimensions :)

This is very nice for allowing this use case. However, what is a bummer that the mouse scrolling characteristic is lost due to this widget.
Users find this to be really unintuitive on web.

Proposal

The InteractiveViewer should have something like a scrollingDirection attribute, which determines the Axis along which a mouse scroll will scroll the InteractiveViewer.

In my example, this would allow to use the mouse scroll wheel (or trackpad scrolling) to scroll vertically while scrolling horizontally still needs a drag.