Function applyProps

packages/fiber/src/core/utils.tsx:401–535

(object: Instance<T>['object'], props: Instance<T>['props'])

// This function applies a set of changes to the instance
export function applyProps<T = any>(object: Instance<T>['object'], props: Instance<T>['props']): Instance<T>['object'] {
  const instance = object.__r3f
  const rootState = instance && findInitialRoot(instance).getState()
  const prevHandlers = instance?.eventCount

  for (const prop in props) {
    let value = props[prop]

    // Don't mutate reserved keys
    if (RESERVED_PROPS.includes(prop)) continue

    // Deal with pointer events, including removing them if undefined
    if (instance && EVENT_REGEX.test(prop)) {
      if (typeof value === 'function') instance.handlers[prop as keyof EventHandlers] = value as any
      else delete instance.handlers[prop as keyof EventHandlers]
      instance.eventCount = Object.keys(instance.handlers).length
      continue
    }

    // Ignore setting undefined props
    // https://github.com/pmndrs/react-three-fiber/issues/274
    if (value === undefined) continue

    let { root, key, target } = resolve(object, prop)

    // Throw an error if we attempted to set a pierced prop to a non-object
    if (target === undefined && (typeof root !== 'object' || root === null)) {
      throw Error(`R3F: Cannot set "${prop}". Ensure it is an object before setting "${key}".`)
    }

    // Layers must be written to the mask property
    if (target instanceof THREE.Layers && value instanceof THREE.Layers) {
      target.mask = value.mask
    }
    // Set colors if valid color representation for automatic conversion (copy)
    else if (target instanceof THREE.Color && isColorRepresentation(value)) {
      target.set(value)
    }
    // Copy if properties match signatures and implement math interface (likely read-only)
    else if (
      target !== null &&
      typeof target === 'object' &&
      typeof target.set === 'function' &&
      typeof target.copy === 'function' &&
      (value as ClassConstructor | null)?.constructor &&
      (target as ClassConstructor).constructor === (value as ClassConstructor).constructor
    ) {
      target.copy(value)
    }
    // Set array types
    else if (
      target !== null &&
      typeof target === 'object' &&
      typeof target.set === 'function' &&
      Array.isArray(value)
    ) {
      if (typeof target.fromArray === 'function') target.fromArray(value)
      else target.set(...value)