Refine top and bottom item anchor calculation

[bryankeller]

Details

This refines our target content offset logic. Previously, we used the closest edge of an item to be an anchor. For example, in a topToBottom layout, we would use the topmost item's top or bottom edge as the anchor for scroll position preservation, depending on which was closest to the top edge. This causes weird issues if the height of an item changes, since it will visually grow upward or downward depending on how close it is to the top of the screen.

I think a simpler and more predictable behavior is to simply always use the top edge of the topmost item as the anchor point. Similarly, for a bottomToTop layout, we'll always use the bottom edge of the bottommost item as the anchor point.

Related Issue

N/A

Motivation and Context

Some weird issues with voting on wish lists, since adding a vote changes the height of the cell. The direction the card grows after resizing changes depending on how close it is to the top edge.

Simulator.Screen.Recording.-.iPhone.15.Pro.-.2024-05-01.at.17.24.39.mp4

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[brynbodayle]

Nice, makes a ton of sense!