While it is common for a mobile application to display one ScrollView at a time,
desktop UI patterns are more likely to display multiple ScrollViews
side-by-side. The prior implementation of PrimaryScrollController conflicted
with this pattern, resulting in an often unhelpful error message. To remedy this,
the PrimaryScrollController has been updated with additional parameters as
well as better error messaging across multiple widgets that depend on it.

Description of change

The previous implementation of ScrollView resulted in primary being true by
default for all vertical ScrollViews that did not already have a
ScrollController, on all platforms. This default behavior was not always clear,
particularly because it is separate from the PrimaryScrollController itself.

// Previously, this ListView would always result in primary being true,

// and attached to the PrimaryScrollController on all platforms.

Scaffold

body:

ListView

builder

itemBuilder:

BuildContext

context