angular-cn/packages/core/src/render3/interfaces/view.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {LContainer} from './container';
import {DirectiveDef} from './definition';
import {LElementNode, LViewNode, TNode} from './node';
import {Renderer3} from './renderer';


/**
 * `LView` stores all of the information needed to process the instructions as
 * they are invoked from the template. Each embedded view and component view has its
 * own `LView`. When processing a particular view, we set the `currentView` to that
 * `LView`. When that view is done processing, the `currentView` is set back to
 * whatever the original `currentView` was before(the parent `LView`).
 *
 * Keeping separate state for each view facilities view insertion / deletion, so we
 * don't have to edit the data array based on which views are present.
 */
export interface LView {
  /**
   * Whether or not the view is in creationMode.
   *
   * This must be stored in the view rather than using `data` as a marker so that
   * we can properly support embedded views. Otherwise, when exiting a child view
   * back into the parent view, `data` will be defined and `creationMode` will be
   * improperly reported as false.
   */
  creationMode: boolean;

  /** The index in the data array at which view hooks begin to be stored. */
  viewHookStartIndex: number|null;

  /**
   * The parent view is needed when we exit the view and must restore the previous
   * `LView`. Without this, the render method would have to keep a stack of
   * views as it is recursively rendering templates.
   */
  readonly parent: LView|null;

  /**
   * Pointer to the `LViewNode` or `LElementNode` which represents the root of the view.
   *
   * If `LViewNode`, this is an embedded view of a container. We need this to be able to
   * efficiently find the `LViewNode` when inserting the view into an anchor.
   *
   * If `LElementNode`, this is the LView of a component.
   */
  readonly node: LViewNode|LElementNode;

  /**
   * ID to determine whether this view is the same as the previous view
   * in this position. If it's not, we know this view needs to be inserted
   * and the one that exists needs to be removed (e.g. if/else statements)
   */
  readonly id: number;

  /** Renderer to be used for this view. */
  readonly renderer: Renderer3;

  /**
   * The binding start index is the index at which the nodes array
   * starts to store bindings only. Saving this value ensures that we
   * will begin reading bindings at the correct point in the array when
   * we are in update mode.
   */
  bindingStartIndex: number|null;

  /**
   * When a view is destroyed, listeners need to be released and onDestroy callbacks
   * need to be called. This cleanup array stores both listener data (in chunks of 4)
   * and onDestroy data (in chunks of 2) for a particular view. Combining the arrays
   * saves on memory (70 bytes per array) and on a few bytes of code size (for two
   * separate for loops).
   *
   * If it's a listener being stored:
   * 1st index is: event name to remove
   * 2nd index is: native element
   * 3rd index is: listener function
   * 4th index is: useCapture boolean
   *
   * If it's an onDestroy function:
   * 1st index is: onDestroy function
   * 2nd index is; context for function
   */
  cleanup: any[]|null;

  /**
   * The first LView or LContainer beneath this LView in the hierarchy.
   *
   * Necessary to store this so views can traverse through their nested views
   * to remove listeners and call onDestroy callbacks.
   *
   * For embedded views, we store the LContainer rather than the first ViewState
   * to avoid managing splicing when views are added/removed.
   */
  child: LView|LContainer|null;

  /**
   * The last LView or LContainer beneath this LView in the hierarchy.
   *
   * The tail allows us to quickly add a new state to the end of the view list
   * without having to propagate starting from the first child.
   */
  tail: LView|LContainer|null;

  /**
   * The next sibling LView or LContainer.
   *
   * Allows us to propagate between sibling view states that aren't in the same
   * container. Embedded views already have a node.next, but it is only set for
   * views in the same container. We need a way to link component views and views
   * across containers as well.
   */
  next: LView|LContainer|null;

  /**
   * This array stores all element/text/container nodes created inside this view
   * and their bindings. Stored as an array rather than a linked list so we can
   * look up nodes directly in the case of forward declaration or bindings
   * (e.g. E(1))..
   *
   * All bindings for a given view are stored in the order in which they
   * appear in the template, starting with `bindingStartIndex`.
   * We use `bindingIndex` to internally keep track of which binding
   * is currently active.
   *
   * NOTE: We also use data == null as a marker for creationMode. We
   * do this by creating ViewState in incomplete state with nodes == null
   * and we initialize it on first run.
   */
  readonly data: any[];

  /**
   * The static data array for the current view. We need a reference to this so we
   * can easily walk up the node tree in DI and get the ngStaticData array associated
   * with a node (where the directive defs are stored).
   */
  ngStaticData: (TNode|DirectiveDef<any>|null)[];
}

/** Interface necessary to work with view tree traversal */
export interface LViewOrLContainer {
  next: LView|LContainer|null;
  child?: LView|LContainer|null;
  views?: LViewNode[];
  parent: LView|null;
}

// Note: This hack is necessary so we don't erroneously get a circular dependency
// failure based on types.
export const unusedValueExportToPlacateAjd = 1;