text: /**
   * @providesModule Touchable
   */
  
  'use strict';
  
  var BoundingDimensions = require('BoundingDimensions');
  var Position = require('Position');
  var TouchEventUtils = require('TouchEventUtils');
  
  var keyMirror = require('keyMirror');
  var queryLayoutByID = require('queryLayoutByID');
  
  /**
   * `Touchable`: Taps done right.
   *
   * You hook your `ResponderEventPlugin` events into `Touchable`. `Touchable`
   * will measure time/geometry and tells you when to give feedback to the user.
   *
   * ====================== Touchable Tutorial ===============================
   * The `Touchable` mixin helps you handle the "press" interaction. It analyzes
   * the geometry of elements, and observes when another responder (scroll view
   * etc) has stolen the touch lock. It notifies your component when it should
   * give feedback to the user. (bouncing/highlighting/unhighlighting).
   *
   * - When a touch was activated (typically you highlight)
   * - When a touch was deactivated (typically you unhighlight)
   * - When a touch was "pressed" - a touch ended while still within the geometry
   *   of the element, and no other element (like scroller) has "stolen" touch
   *   lock ("responder") (Typically you bounce the element).
   *
   * A good tap interaction isn't as simple as you might think. There should be a
   * slight delay before showing a highlight when starting a touch. If a
   * subsequent touch move exceeds the boundary of the elemement, it should
   * unhighlight, but if that same touch is brought back within the boundary, it
   * should rehighlight again. A touch can move in and out of that boundary
   * several times, each time toggling highlighting, but a "press" is only
   * triggered if that touch ends while within the element's boundary and no
   * scroller (or anything else) has stolen the lock on touches.
   *
   * To create a new type of component that handles interaction using the
   * `Touchable` mixin, do the following:
   *
   * - Initialize the `Touchable` state.
   *
   *   getInitialState: function() {
   *     return merge(this.touchableGetInitialState(), yourComponentState);
   *   }
   *
   * - Choose the rendered component who's touches should start the interactive
   *   sequence. On that rendered node, forward all `Touchable` responder
   *   handlers. You can choose any rendered node you like. Choose a node who's
   *   hit target you'd like to instigate the interaction sequence:
   *
   *   // In render function:
   *   return (
   *     <div
   *       onStartShouldSetResponder={this.touchableHandleStartShouldSetResponder}
   *       onResponderTerminationRequest={this.touchableHandleResponderTerminationRequest}
   *       onResponderGrant={this.touchableHandleResponderGrant}
   *       onResponderMove={this.touchableHandleResponderMove}
   *       onResponderRelease={this.touchableHandleResponderRelease}
   *       onResponderTerminate={this.touchableHandleResponderTerminate}>
   *       <div>
   *         Even though the hit detection/interactions are triggered by the
   *         wrapping (typically larger) node, we usually end up implementing
   *         custom logic that highlights this inner one.
   *       </div>
   *     </div>
   *   );
   *
   * - You may set up your own handlers for each of these events, so long as you
   *   also invoke the `touchable*` handlers inside of your custom handler.
   *
   * - Implement the handlers on your component class in order to provide
   *   feedback to the user. See documentation for each of these class methods
   *   that you should implement.
   *
   *   touchableHandlePress: function() {
   *      this.performBounceAnimation();  // or whatever you want to do.
   *   },
   *   touchableHandleActivePressIn: function() {
   *     this.beginHighlighting(...);  // Whatever you like to convey activation
   *   },
   *   touchableHandleActivePressOut: function() {
   *     this.endHighlighting(...);  // Whatever you like to convey deactivation
   *   },
   *
   * - There are more advanced methods you can implement (see documentation below):
   *   touchableGetHighlightDelayMS: function() {
   *     return 20;
   *   }
   *   // In practice, *always* use a predeclared constant (conserve memory).
   *   touchableGetPressRectOffset: function() {
   *     return {top: 20, left: 20, right: 20, bottom: 100};
   *   }
   */
  
  /**
   * Touchable states.
   */
  var States = keyMirror({
    NOT_RESPONDER: null,                   // Not the responder
    RESPONDER_INACTIVE_PRESS_IN: null,     // Responder, inactive, in the `PressRect`
    RESPONDER_INACTIVE_PRESS_OUT: null,    // Responder, inactive, out of `PressRect`
    RESPONDER_ACTIVE_PRESS_IN: null,       // Responder, active, in the `PressRect`
    RESPONDER_ACTIVE_PRESS_OUT: null,      // Responder, active, out of `PressRect`
    RESPONDER_ACTIVE_LONG_PRESS_IN: null,  // Responder, active, in the `PressRect`, after long press threshold
    RESPONDER_ACTIVE_LONG_PRESS_OUT: null, // Responder, active, out of `PressRect`, after long press threshold
    ERROR: null
  });
  
  /**
   * Quick lookup map for states that are considered to be "active"
   */
  var IsActive = {
    RESPONDER_ACTIVE_PRESS_OUT: true,
    RESPONDER_ACTIVE_PRESS_IN: true
  };
  
  /**
   * Quick lookup for states that are considered to be "pressing" and are
   * therefore eligible to result in a "selection" if the press stops.
   */
  var IsPressingIn = {
    RESPONDER_INACTIVE_PRESS_IN: true,
    RESPONDER_ACTIVE_PRESS_IN: true,
    RESPONDER_ACTIVE_LONG_PRESS_IN: true,
  };
  
  var IsLongPressingIn = {
    RESPONDER_ACTIVE_LONG_PRESS_IN: true,
  };
  
  /**
   * Inputs to the state machine.
   */
  var Signals = keyMirror({
    DELAY: null,
    RESPONDER_GRANT: null,
    RESPONDER_RELEASE: null,
    RESPONDER_TERMINATED: null,
    ENTER_PRESS_RECT: null,
    LEAVE_PRESS_RECT: null,
    LONG_PRESS_DETECTED: null,
  });
  
  /**
   * Mapping from States x Signals => States
   */
  var Transitions = {
    NOT_RESPONDER: {
      DELAY: States.ERROR,
      RESPONDER_GRANT: States.RESPONDER_INACTIVE_PRESS_IN,
      RESPONDER_RELEASE: States.ERROR,
      RESPONDER_TERMINATED: States.ERROR,
      ENTER_PRESS_RECT: States.ERROR,
      LEAVE_PRESS_RECT: States.ERROR,
      LONG_PRESS_DETECTED: States.ERROR,
    },
    RESPONDER_INACTIVE_PRESS_IN: {
      DELAY: States.RESPONDER_ACTIVE_PRESS_IN,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_INACTIVE_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_INACTIVE_PRESS_OUT,
      LONG_PRESS_DETECTED: States.ERROR,
    },
    RESPONDER_INACTIVE_PRESS_OUT: {
      DELAY: States.RESPONDER_ACTIVE_PRESS_OUT,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_INACTIVE_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_INACTIVE_PRESS_OUT,
      LONG_PRESS_DETECTED: States.ERROR,
    },
    RESPONDER_ACTIVE_PRESS_IN: {
      DELAY: States.ERROR,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_ACTIVE_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_ACTIVE_PRESS_OUT,
      LONG_PRESS_DETECTED: States.RESPONDER_ACTIVE_LONG_PRESS_IN,
    },
    RESPONDER_ACTIVE_PRESS_OUT: {
      DELAY: States.ERROR,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_ACTIVE_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_ACTIVE_PRESS_OUT,
      LONG_PRESS_DETECTED: States.ERROR,
    },
    RESPONDER_ACTIVE_LONG_PRESS_IN: {
      DELAY: States.ERROR,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_ACTIVE_LONG_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_ACTIVE_LONG_PRESS_OUT,
      LONG_PRESS_DETECTED: States.RESPONDER_ACTIVE_LONG_PRESS_IN,
    },
    RESPONDER_ACTIVE_LONG_PRESS_OUT: {
      DELAY: States.ERROR,
      RESPONDER_GRANT: States.ERROR,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.RESPONDER_ACTIVE_LONG_PRESS_IN,
      LEAVE_PRESS_RECT: States.RESPONDER_ACTIVE_LONG_PRESS_OUT,
      LONG_PRESS_DETECTED: States.ERROR,
    },
    error: {
      DELAY: States.NOT_RESPONDER,
      RESPONDER_GRANT: States.RESPONDER_INACTIVE_PRESS_IN,
      RESPONDER_RELEASE: States.NOT_RESPONDER,
      RESPONDER_TERMINATED: States.NOT_RESPONDER,
      ENTER_PRESS_RECT: States.NOT_RESPONDER,
      LEAVE_PRESS_RECT: States.NOT_RESPONDER,
      LONG_PRESS_DETECTED: States.NOT_RESPONDER,
    }
  };
  
  // ==== Typical Constants for integrating into UI components ====
  // var HIT_EXPAND_PX = 20;
  // var HIT_VERT_OFFSET_PX = 10;
  var HIGHLIGHT_DELAY_MS = 130;
  
  var PRESS_EXPAND_PX = 20;
  
  var LONG_PRESS_THRESHOLD = 500;
  
  var LONG_PRESS_DELAY_MS = LONG_PRESS_THRESHOLD - HIGHLIGHT_DELAY_MS;
  
  var LONG_PRESS_ALLOWED_MOVEMENT = 10;
  
  // Default amount "active" region protrudes beyond box
  
  /**
   * By convention, methods prefixed with underscores are meant to be @private,
   * and not @protected. Mixers shouldn't access them - not even to provide them
   * as callback handlers.
   *
   *
   * ========== Geometry =========
   * `Touchable` only assumes that there exists a `HitRect` node. The `PressRect`
   * is an abstract box that is extended beyond the `HitRect`.
   *
   *  +--------------------------+
   *  |                          | - "Start" events in `HitRect` cause `HitRect`
   *  |  +--------------------+  |   to become the responder.
   *  |  |  +--------------+  |  | - `HitRect` is typically expanded around
   *  |  |  |              |  |  |   the `VisualRect`, but shifted downward.
   *  |  |  |  VisualRect  |  |  | - After pressing down, after some delay,
   *  |  |  |              |  |  |   and before letting up, the Visual React
   *  |  |  +--------------+  |  |   will become "active". This makes it eligible
   *  |  |     HitRect        |  |   for being highlighted (so long as the
   *  |  +--------------------+  |   press remains in the `PressRect`).
   *  |        PressRect     o   |
   *  +----------------------|---+
   *           Out Region    |
   *                         +-----+ This gap between the `HitRect` and
   *                                 `PressRect` allows a touch to move far away
   *                                 from the original hit rect, and remain
   *                                 highlighted, and eligible for a "Press".
   *                                 Customize this via
   *                                 `touchableGetPressRectOffset()`.
   *
   *
   *
   * ======= State Machine =======
   *
   * +-------------+ <---+ RESPONDER_RELEASE
   * |NOT_RESPONDER|
   * +-------------+ <---+ RESPONDER_TERMINATED
   *     +
   *     | RESPONDER_GRANT (HitRect)
   *     v
   * +---------------------------+  DELAY   +-------------------------+  T + DELAY     +------------------------------+
   * |RESPONDER_INACTIVE_PRESS_IN|+-------->|RESPONDER_ACTIVE_PRESS_IN| +------------> |RESPONDER_ACTIVE_LONG_PRESS_IN|
   * +---------------------------+          +-------------------------+                +------------------------------+
   *     +            ^                         +           ^                                 +           ^
   *     |LEAVE_      |ENTER_                   |LEAVE_     |ENTER_                           |LEAVE_     |ENTER_
   *     |PRESS_RECT  |PRESS_RECT               |PRESS_RECT |PRESS_RECT                       |PRESS_RECT |PRESS_RECT
   *     |            |                         |           |                                 |           |
   *     v            +                         v           +                                 v           +
   * +----------------------------+  DELAY  +--------------------------+               +-------------------------------+
   * |RESPONDER_INACTIVE_PRESS_OUT|+------->|RESPONDER_ACTIVE_PRESS_OUT|               |RESPONDER_ACTIVE_LONG_PRESS_OUT|
   * +----------------------------+         +--------------------------+               +-------------------------------+
   *
   * T + DELAY => LONG_PRESS_DELAY_MS + DELAY
   *
   * Not drawn are the side effects of each transition. The most important side
   * effect is the `touchableHandlePress` abstract method invocation that occurs
   * when a responder is released while in either of the "Press" states.
   *
   * The other important side effects are the highlight abstract method
   * invocations (internal callbacks) to be implemented by the mixer.
   *
   *
   * @lends Touchable.prototype
   */
  var TouchableMixin = {
    /**
     * It's prefer that mixins determine state in this way, having the class
     * explicitly mix the state in the one and only `getInitialState` method.
     *
     * @return {object} State object to be placed inside of
     * `this.state.touchable`.
     */
    touchableGetInitialState: function() {
      return {
        touchable: {touchState: undefined, responderID: null}
      };
    },
  
    // ==== Hooks to Gesture Responder system ====
    /**
     * Must return true if embedded in a native platform scroll view.
     */
    touchableHandleResponderTerminationRequest: function() {
      return !this.props.rejectResponderTermination;
    },
  
    /**
     * Must return true to start the process of `Touchable`.
     */
    touchableHandleStartShouldSetResponder: function() {
      return true;
    },
  
    /**
     * Return true to cancel press on long press.
     */
    touchableLongPressCancelsPress: function () {
      return true;
    },
  
    /**
     * Place as callback for a DOM element's `onResponderGrant` event.
     * @param {SyntheticEvent} e Synthetic event from event system.
     * @param {string} dispatchID ID of node that e was dispatched to.
     *
     */
    touchableHandleResponderGrant: function(e, dispatchID) {
      // Since e is used in a callback invoked on another event loop
      // (as in setTimeout etc), we need to call e.persist() on the
      // event to make sure it doesn't get reused in the event object pool.
      e.persist();
  
      this.pressOutDelayTimeout && clearTimeout(this.pressOutDelayTimeout);
      this.pressOutDelayTimeout = null;
  
      this.state.touchable.touchState = States.NOT_RESPONDER;
      this.state.touchable.responderID = dispatchID;
      this._receiveSignal(Signals.RESPONDER_GRANT, e);
      var delayMS =
        this.touchableGetHighlightDelayMS !== undefined ?
        Math.max(this.touchableGetHighlightDelayMS(), 0) : HIGHLIGHT_DELAY_MS;
      delayMS = isNaN(delayMS) ? HIGHLIGHT_DELAY_MS : delayMS;
      if (delayMS !== 0) {
        this.touchableDelayTimeout = setTimeout(
          this._handleDelay.bind(this, e),
          delayMS
        );
      } else {
        this._handleDelay(e);
      }
  
      var longDelayMS =
        this.touchableGetLongPressDelayMS !== undefined ?
        Math.max(this.touchableGetLongPressDelayMS(), 10) : LONG_PRESS_DELAY_MS;
      longDelayMS = isNaN(longDelayMS) ? LONG_PRESS_DELAY_MS : longDelayMS;
      this.longPressDelayTimeout = setTimeout(
        this._handleLongDelay.bind(this, e),
        longDelayMS + delayMS
      );
    },
  
    /**
     * Place as callback for a DOM element's `onResponderRelease` event.
     */
    touchableHandleResponderRelease: function(e) {
      this._receiveSignal(Signals.RESPONDER_RELEASE, e);
    },
  
    /**
     * Place as callback for a DOM element's `onResponderTerminate` event.
     */
    touchableHandleResponderTerminate: function(e) {
      this._receiveSignal(Signals.RESPONDER_TERMINATED, e);
    },
  
    /**
     * Place as callback for a DOM element's `onResponderMove` event.
     */
    touchableHandleResponderMove: function(e) {
      // Not enough time elapsed yet, wait for highlight -
      // this is just a perf optimization.
      if (this.state.touchable.touchState === States.RESPONDER_INACTIVE_PRESS_IN) {
        return;
      }
  
      // Measurement may not have returned yet.
      if (!this.state.touchable.positionOnActivate) {
        return;
      }
  
      var positionOnActivate = this.state.touchable.positionOnActivate;
      var dimensionsOnActivate = this.state.touchable.dimensionsOnActivate;
      var pressRectOffset = this.touchableGetPressRectOffset ?
        this.touchableGetPressRectOffset() : null;
      var pressExpandLeft =
        pressRectOffset.left != null ? pressRectOffset.left : PRESS_EXPAND_PX;
      var pressExpandTop =
        pressRectOffset.top != null ? pressRectOffset.top : PRESS_EXPAND_PX;
      var pressExpandRight =
        pressRectOffset.right != null ? pressRectOffset.right : PRESS_EXPAND_PX;
      var pressExpandBottom =
        pressRectOffset.bottom != null ? pressRectOffset.bottom : PRESS_EXPAND_PX;
  
      var touch = TouchEventUtils.extractSingleTouch(e.nativeEvent);
      var pageX = touch && touch.pageX;
      var pageY = touch && touch.pageY;
  
      if (this.pressInLocation) {
        var movedDistance = this._getDistanceBetweenPoints(pageX, pageY, this.pressInLocation.pageX, this.pressInLocation.pageY);
        if (movedDistance > LONG_PRESS_ALLOWED_MOVEMENT) {
          this._cancelLongPressDelayTimeout();
        }
      }
  
      var isTouchWithinActive =
          pageX > positionOnActivate.left - pressExpandLeft &&
          pageY > positionOnActivate.top - pressExpandTop &&
          pageX <
            positionOnActivate.left +
            dimensionsOnActivate.width +
            pressExpandRight &&
          pageY <
            positionOnActivate.top +
            dimensionsOnActivate.height +
            pressExpandBottom;
      if (isTouchWithinActive) {
        this._receiveSignal(Signals.ENTER_PRESS_RECT, e);
      } else {
        this._cancelLongPressDelayTimeout();
        this._receiveSignal(Signals.LEAVE_PRESS_RECT, e);
      }
    },
  
    // ==== Abstract Application Callbacks ====
  
    /**
     * Invoked when the item should be highlighted. Mixers should implement this
     * to visually distinguish the `VisualRect` so that the user knows that
     * releasing a touch will result in a "selection" (analog to click).
     *
     * @abstract
     * touchableHandleActivePressIn: function,
     */
  
    /**
     * Invoked when the item is "active" (in that it is still eligible to become
     * a "select") but the touch has left the `PressRect`. Usually the mixer will
     * want to unhighlight the `VisualRect`. If the user (while pressing) moves
     * back into the `PressRect` `touchableHandleActivePressIn` will be invoked
     * again and the mixer should probably highlight the `VisualRect` again. This
     * event will not fire on an `touchEnd/mouseUp` event, only move events while
     * the user is depressing the mouse/touch.
     *
     * @abstract
     * touchableHandleActivePressOut: function
     */
  
    /**
     * Invoked when the item is "selected" - meaning the interaction ended by
     * letting up while the item was either in the state
     * `RESPONDER_ACTIVE_PRESS_IN` or `RESPONDER_INACTIVE_PRESS_IN`.
     *
     * @abstract
     * touchableHandlePress: function
     */
  
    /**
     * Invoked when the item is long pressed - meaning the interaction ended by
     * letting up while the item was in `RESPONDER_ACTIVE_LONG_PRESS_IN`. If
     * `touchableHandleLongPress` is *not* provided, `touchableHandlePress` will
     * be called as it normally is. If `touchableHandleLongPress` is provided, by
     * default any `touchableHandlePress` callback will not be invoked. To
     * override this default behavior, override `touchableLongPressCancelsPress`
     * to return false. As a result, `touchableHandlePress` will be called when
     * lifting up, even if `touchableHandleLongPress` has also been called.
     *
     * @abstract
     * touchableHandleLongPress: function
     */
  
    /**
     * Returns the number of millis to wait before triggering a highlight.
     *
     * @abstract
     * touchableGetHighlightDelayMS: function
     */
  
    /**
     * Returns the amount to extend the `HitRect` into the `PressRect`. Positive
     * numbers mean the size expands outwards.
     *
     * @abstract
     * touchableGetPressRectOffset: function
     */
  
  
  
    // ==== Internal Logic ====
  
    /**
     * Measures the `HitRect` node on activation. The Bounding rectangle is with
     * respect to viewport - not page, so adding the `pageXOffset/pageYOffset`
     * should result in points that are in the same coordinate system as an
     * event's `globalX/globalY` data values.
     *
     * - Consider caching this for the lifetime of the component, or possibly
     *   being able to share this cache between any `ScrollMap` view.
     *
     * @sideeffects
     * @private
     */
    _remeasureMetricsOnActivation: function() {
      queryLayoutByID(
        this.state.touchable.responderID,
        null,
        this._handleQueryLayout
      );
    },
  
    _handleQueryLayout: function(l, t, w, h, globalX, globalY) {
      this.state.touchable.positionOnActivate &&
        Position.release(this.state.touchable.positionOnActivate);
      this.state.touchable.dimensionsOnActivate &&
        BoundingDimensions.release(this.state.touchable.dimensionsOnActivate);
      this.state.touchable.positionOnActivate = Position.getPooled(globalX, globalY);
      this.state.touchable.dimensionsOnActivate = BoundingDimensions.getPooled(w, h);
    },
  
    _handleDelay: function(e) {
      this.touchableDelayTimeout = null;
      this._receiveSignal(Signals.DELAY, e);
    },
  
    _handleLongDelay: function(e) {
      this.longPressDelayTimeout = null;
      this._receiveSignal(Signals.LONG_PRESS_DETECTED, e);
    },
  
    /**
     * Receives a state machine signal, performs side effects of the transition
     * and stores the new state. Validates the transition as well.
     *
     * @param {Signals} signal State machine signal.
     * @throws Error if invalid state transition or unrecognized signal.
     * @sideeffects
     */
    _receiveSignal: function(signal, e) {
      var curState = this.state.touchable.touchState;
      if (!(Transitions[curState] && Transitions[curState][signal])) {
        throw new Error(
          'Unrecognized signal `' + signal + '` or state `' + curState +
          '` for Touchable responder `' + this.state.touchable.responderID + '`'
        );
      }
      var nextState = Transitions[curState][signal];
      if (nextState === States.ERROR) {
        throw new Error(
          'Touchable cannot transition from `' + curState + '` to `' + signal +
          '` for responder `' + this.state.touchable.responderID + '`'
        );
      }
      if (curState !== nextState) {
        this._performSideEffectsForTransition(curState, nextState, signal, e);
        this.state.touchable.touchState = nextState;
      }
    },
  
    _cancelLongPressDelayTimeout: function () {
      this.longPressDelayTimeout && clearTimeout(this.longPressDelayTimeout);
      this.longPressDelayTimeout = null;
    },
  
    _isHighlight: function (state) {
      return state === States.RESPONDER_ACTIVE_PRESS_IN ||
             state === States.RESPONDER_ACTIVE_LONG_PRESS_IN;
    },
  
    _savePressInLocation: function(e) {
      var touch = TouchEventUtils.extractSingleTouch(e.nativeEvent);
      var pageX = touch && touch.pageX;
      var pageY = touch && touch.pageY;
      this.pressInLocation = {pageX: pageX, pageY: pageY};
    },
  
    _getDistanceBetweenPoints: function (aX, aY, bX, bY) {
      var deltaX = aX - bX;
      var deltaY = aY - bY;
      return Math.sqrt(deltaX * deltaX + deltaY * deltaY);
    },
  
    /**
     * Will perform a transition between touchable states, and identify any
     * highlighting or unhighlighting that must be performed for this particular
     * transition.
     *
     * @param {States} curState Current Touchable state.
     * @param {States} nextState Next Touchable state.
     * @param {Signal} signal Signal that triggered the transition.
     * @param {Event} e Native event.
     * @sideeffects
     */
    _performSideEffectsForTransition: function(curState, nextState, signal, e) {
      var curIsHighlight = this._isHighlight(curState);
      var newIsHighlight = this._isHighlight(nextState);
  
      var isFinalSignal =
        signal === Signals.RESPONDER_TERMINATED ||
        signal === Signals.RESPONDER_RELEASE;
  
      if (isFinalSignal) {
        this._cancelLongPressDelayTimeout();
      }
  
      if (!IsActive[curState] && IsActive[nextState]) {
        this._remeasureMetricsOnActivation();
      }
  
      if (IsPressingIn[curState] && signal === Signals.LONG_PRESS_DETECTED) {
        this.touchableHandleLongPress && this.touchableHandleLongPress(e);
      }
  
      if (newIsHighlight && !curIsHighlight) {
        this._savePressInLocation(e);
        this.touchableHandleActivePressIn && this.touchableHandleActivePressIn(e);
      } else if (!newIsHighlight && curIsHighlight && this.touchableHandleActivePressOut) {
        if (this.touchableGetPressOutDelayMS && this.touchableGetPressOutDelayMS()) {
          this.pressOutDelayTimeout = this.setTimeout(function() {
            this.touchableHandleActivePressOut(e);
          }, this.touchableGetPressOutDelayMS());
        } else {
          this.touchableHandleActivePressOut(e);
        }
      }
  
      if (IsPressingIn[curState] && signal === Signals.RESPONDER_RELEASE) {
        var hasLongPressHandler = !!this.props.onLongPress;
        var pressIsLongButStillCallOnPress =
          IsLongPressingIn[curState] && (    // We *are* long pressing..
            !hasLongPressHandler ||          // But either has no long handler
            !this.touchableLongPressCancelsPress() // or we're told to ignore it.
          );
  
        var shouldInvokePress =  !IsLongPressingIn[curState] || pressIsLongButStillCallOnPress;
        if (shouldInvokePress && this.touchableHandlePress) {
          this.touchableHandlePress(e);
        }
      }
  
      this.touchableDelayTimeout && clearTimeout(this.touchableDelayTimeout);
      this.touchableDelayTimeout = null;
    }
  
  };
  
  var Touchable = {
    Mixin: TouchableMixin
  };
  
  module.exports = Touchable;
  