[Bron Davies (brondavies)]

Summary:

Fixes #3147. On the new architecture a macOS ScrollView has no inverted prop, and VirtualizedList leaves out its inversion style on macOS, so an inverted list isn't inverted.

• VirtualizedList uses the inversion style on macOS under the new architecture, as on iOS. Layout and measurement (measureInWindow) then match what's drawn.

• RCTScrollViewComponentView turns a vertical scaleY(-1) into flipped coordinates rather than a layer transform:

  • the document view and the content view count from the bottom;
  • the cells' own scaleY(-1) is left off.

  AppKit then hit-tests, tracks hover and scrolls with the wheel the right way. A content offset still counts from the first item.

• Turning inverted on or off re-sets the document view, because the clip view reads its document's flippedness only then. The view also sends the settled scroll offset afterwards.

Horizontal inverted lists keep the layer transform.

Test Plan:

RNTester-macOS (Debug, arm64, Xcode 27.1, macOS 26.6.2). The Playground had an inverted FlatList of 30 Pressable rows, 40pt each, in a 300pt list, with the onScroll offset shown above it.

• On main, Item 0 is at the top.
• With this change, Item 0 is at the bottom. Three wheel notches up, sent from lldb, bring Items 2 to 9 into view. Native and onScroll both report offset 90.
• Hit-testing at the point where measureInWindow puts Item 5 returns Item 5's view, which is where it's drawn.

It's the same in an app on 0.83.0, where the inverted list is a chat that switches inverted on once its first messages arrive.

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.