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/** * Patch flags are optimization hints generated by the compiler. * when a block with dynamicChildren is encountered during diff, the algorithm * enters "optimized mode". In this mode, we know that the vdom is produced by * a render function generated by the compiler, so the algorithm only needs to * handle updates explicitly marked by these patch flags. * * Patch flags can be combined using the | bitwise operator and can be checked * using the & operator, e.g. * * ```js * const flag = TEXT | CLASS * if (flag & TEXT) { ... } * ``` * * Check the `patchElement` function in '../../runtime-core/src/renderer.ts' to see how the * flags are handled during diff. */export const enum PatchFlags {  /**   * Indicates an element with dynamic textContent (children fast path)   */  TEXT = 1,
  /**   * Indicates an element with dynamic class binding.   */  CLASS = 1 << 1,
  /**   * Indicates an element with dynamic style   * The compiler pre-compiles static string styles into static objects   * + detects and hoists inline static objects   * e.g. `style="color: red"` and `:style="{ color: 'red' }"` both get hoisted   * as:   * ```js   * const style = { color: 'red' }   * render() { return e('div', { style }) }   * ```   */  STYLE = 1 << 2,
  /**   * Indicates an element that has non-class/style dynamic props.   * Can also be on a component that has any dynamic props (includes   * class/style). when this flag is present, the vnode also has a dynamicProps   * array that contains the keys of the props that may change so the runtime   * can diff them faster (without having to worry about removed props)   */  PROPS = 1 << 3,
  /**   * Indicates an element with props with dynamic keys. When keys change, a full   * diff is always needed to remove the old key. This flag is mutually   * exclusive with CLASS, STYLE and PROPS.   */  FULL_PROPS = 1 << 4,
  /**   * Indicates an element with event listeners (which need to be attached   * during hydration)   */  HYDRATE_EVENTS = 1 << 5,
  /**   * Indicates a fragment whose children order doesn't change.   */  STABLE_FRAGMENT = 1 << 6,
  /**   * Indicates a fragment with keyed or partially keyed children   */  KEYED_FRAGMENT = 1 << 7,
  /**   * Indicates a fragment with unkeyed children.   */  UNKEYED_FRAGMENT = 1 << 8,
  /**   * Indicates an element that only needs non-props patching, e.g. ref or   * directives (onVnodeXXX hooks). since every patched vnode checks for refs   * and onVnodeXXX hooks, it simply marks the vnode so that a parent block   * will track it.   */  NEED_PATCH = 1 << 9,
  /**   * Indicates a component with dynamic slots (e.g. slot that references a v-for   * iterated value, or dynamic slot names).   * Components with this flag are always force updated.   */  DYNAMIC_SLOTS = 1 << 10,
  /**   * Indicates a fragment that was created only because the user has placed   * comments at the root level of a template. This is a dev-only flag since   * comments are stripped in production.   */  DEV_ROOT_FRAGMENT = 1 << 11,
  /**   * SPECIAL FLAGS -------------------------------------------------------------   * Special flags are negative integers. They are never matched against using   * bitwise operators (bitwise matching should only happen in branches where   * patchFlag > 0), and are mutually exclusive. When checking for a special   * flag, simply check patchFlag === FLAG.   */
  /**   * Indicates a hoisted static vnode. This is a hint for hydration to skip   * the entire sub tree since static content never needs to be updated.   */  HOISTED = -1,  /**   * A special flag that indicates that the diffing algorithm should bail out   * of optimized mode. For example, on block fragments created by renderSlot()   * when encountering non-compiler generated slots (i.e. manually written   * render functions, which should always be fully diffed)   * OR manually cloneVNodes   */  BAIL = -2}
/** * dev only flag -> name mapping */export const PatchFlagNames = {  [PatchFlags.TEXT]: `TEXT`,  [PatchFlags.CLASS]: `CLASS`,  [PatchFlags.STYLE]: `STYLE`,  [PatchFlags.PROPS]: `PROPS`,  [PatchFlags.FULL_PROPS]: `FULL_PROPS`,  [PatchFlags.HYDRATE_EVENTS]: `HYDRATE_EVENTS`,  [PatchFlags.STABLE_FRAGMENT]: `STABLE_FRAGMENT`,  [PatchFlags.KEYED_FRAGMENT]: `KEYED_FRAGMENT`,  [PatchFlags.UNKEYED_FRAGMENT]: `UNKEYED_FRAGMENT`,  [PatchFlags.NEED_PATCH]: `NEED_PATCH`,  [PatchFlags.DYNAMIC_SLOTS]: `DYNAMIC_SLOTS`,  [PatchFlags.DEV_ROOT_FRAGMENT]: `DEV_ROOT_FRAGMENT`,  [PatchFlags.HOISTED]: `HOISTED`,  [PatchFlags.BAIL]: `BAIL`}