tree c4bcefa523e20b53884a65bc156e418ec782a3f3
parent e6d42a74d28a2ea51e982786beb3942268776daf
author Chris Bracken <chris@bracken.jp> 1667412643 -0700
committer GitHub <noreply@github.com> 1667412643 -0700
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Scroll 75% of x, y on each list scroll increment (#824)

The gallery driver test includes logic to scroll through various lists
of demos in order to transition to each one. These lists include the
horizontally-scrolling studies list at the top of the gallery home page,
as well as the vertically-scrolling Material, Cupertino, and Other
demo lists on the same page.

TestDriver.scrollUntilVisible scrolls a parent list widget in increments
of dx and/or dy until the specified list item widget is visible. The
Studies carousel list at the top of the gallery home screen has scroll
physics that snap items to the starting edge of the widget. If the dx
scroll distance is too small, the Studies list doesn't scroll far enough
and snaps back to its original position. Conversely, if it scrolls too
far, it may scroll one widget too far and snap the next widget into
place. Instead, we now scroll 75% of the carousel width (empirically
determined) as an attempt at a value in the Goldilocks Zone.

Related: https://github.com/flutter/gallery/pull/792
Related: https://github.com/flutter/flutter/issues/111131

Issue: https://github.com/flutter/flutter/issues/114025