Animate Transform and Opacity Instead of Layout Properties

Avoid animating width, height, top, left, margin, or padding. These trigger layout recalculation on every frame. Instead, use transform (scale, translate) and opacity which run on the GPU without triggering layout.

Incorrect (animates height, triggers layout every frame):

tsx

import Animated, { useAnimatedStyle, withTiming } from 'react-native-reanimated'

function CollapsiblePanel({ expanded }: { expanded: boolean }) {
  const animatedStyle = useAnimatedStyle(() => ({
    height: withTiming(expanded ? 200 : 0), // triggers layout on every frame
    overflow: 'hidden',
  }))

  return <Animated.View style={animatedStyle}>{children}</Animated.View>
}

Correct (animates scaleY, GPU-accelerated):

tsx

import Animated, { useAnimatedStyle, withTiming } from 'react-native-reanimated'

function CollapsiblePanel({ expanded }: { expanded: boolean }) {
  const animatedStyle = useAnimatedStyle(() => ({
    transform: [
      { scaleY: withTiming(expanded ? 1 : 0) },
    ],
    opacity: withTiming(expanded ? 1 : 0),
  }))

  return (
    <Animated.View style={[{ height: 200, transformOrigin: 'top' }, animatedStyle]}>
      {children}
    </Animated.View>
  )
}

Correct (animates translateY for slide animations):

tsx

import Animated, { useAnimatedStyle, withTiming } from 'react-native-reanimated'

function SlideIn({ visible }: { visible: boolean }) {
  const animatedStyle = useAnimatedStyle(() => ({
    transform: [
      { translateY: withTiming(visible ? 0 : 100) },
    ],
    opacity: withTiming(visible ? 1 : 0),
  }))

  return <Animated.View style={animatedStyle}>{children}</Animated.View>
}

GPU-accelerated properties: transform (translate, scale, rotate), opacity. Everything else triggers layout.