scaleEffect now takes number | { x: number; y: number }. When passed a number, TS normalizes it to { x, y } before hitting native. Swift side is a straight pass-through to content.scaleEffect(x: x, y: y). Same structure as OffsetModifier (non-optional @Field vars with identity defaults, single-line body).

Usage: Inverted List

Flip the List vertically, flip each row back, reverse the data — messages anchor to the bottom and new content pushes up naturally:

import { Group, HStack, List, Spacer, Text } from "@expo/ui/swift-ui";
import { listStyle, scaleEffect, scrollContentBackground } from "@expo/ui/swift-ui/modifiers";

function MessageList({ messages }: { messages: { id: string; text: string }[] }) {
  return (
    <List
      modifiers={[
        listStyle("plain"),
        scrollContentBackground("hidden"),
        scaleEffect({ x: 1, y: -1 }),
      ]}
    >
      {[...messages].reverse().map((msg) => (
        <Group key={msg.id} modifiers={[scaleEffect({ x: 1, y: -1 })]}>
          <HStack>
            <Text>{msg.text}</Text>
            <Spacer />
          </HStack>
        </Group>
      ))}
    </List>
  );
}

Existing scaleEffect(number) calls still work — scaleEffect(0.5) normalizes to { x: 0.5, y: 0.5 }.

Changes

Only touches modifiers:

• src/swift-ui/modifiers/index.ts: union type, typeof dispatch (+2/-1)
• ios/Modifiers/ViewModifierRegistry.swift: @Field var x/y with 1.0 defaults (+2/-2)
• CHANGELOG.md: single entry
• build/ type declarations rebuilt

Test Plan

yarn clean, yarn lint --fix, yarn lint, yarn build all pass. yarn test has no test suites in expo-ui (exits with "No tests found"). Rebased on upstream/main.

Existing scaleEffect(number) calls still work since the TS layer normalizes scaleEffect(0.5) to { x: 0.5, y: 0.5 }. Per-axis usage: scaleEffect({ x: 1, y: -1 }) passes x and y directly to native.