Move client/{base, observable, layout, touch, util, view} to samples/ui_lib .

client/touch/TouchHandler.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-/**
- * Touch Handler. Class that handles all touch events and
- * uses them to interpret higher level gestures and behaviors. TouchEvent is a
- * built in mobile safari type:
- * [http://developer.apple.com/safari/library/documentation/UserExperience/Reference/TouchEventClassReference/TouchEvent/TouchEvent.html].
- *
- * Examples of higher level gestures this class is intended to support
- * - click, double click, long click
- * - dragging, swiping, zooming
- *
- * Touch Behavior:
- *      Use this class to make your elements 'touchable' (see Touchable.dart).
- *      Intended to work with all webkit browsers.
- *
- * Drag Behavior:
- *      Use this class to make your elements 'draggable' (see draggable.js).
- *      This behavior will handle all of the required events and report the
- *      properties of the drag to you while the touch is happening and at the
- *      end of the drag sequence. This behavior will NOT perform the actual
- *      dragging (redrawing the element) for you, this responsibility is left to
- *      the client code. This behavior contains a work around for a mobile
- *      safari bug where the 'touchend' event is not dispatched when the touch
- *      goes past the bottom of the browser window.
- *      This is intended to work well in iframes.
- *      Intended to work with all webkit browsers, tested only on iPhone 3.x so
- *      far.
- *
- * Click Behavior:
- *      Not yet implemented.
- *
- * Zoom Behavior:
- *      Not yet implemented.
- *
- * Swipe Behavior:
- *      Not yet implemented.
- */
-class TouchHandler {
-  Touchable _touchable;
-  Element _element;
-
-  /** The absolute sum of all touch y deltas. */
-  int _totalMoveY;
-
-  /** The absolute sum of all touch x deltas. */
-  int _totalMoveX;
-
-  /**
-   * A list of tuples where the first item is the horizontal component of a
-   * recent relevant touch and the second item is the touch's time stamp. Old
-   * touches are removed based on the max tracking time and when direction
-   * changes.
-   */
-  List<int> _recentTouchesX;
-
-  /**
-   * A list of tuples where the first item is the vertical component of a
-   * recent relevant touch and the second item is the touch's time stamp. Old
-   * touches are removed based on the max tracking time and when direction
-   * changes.
-   */
-  List<int> _recentTouchesY;
-
-  // TODO(jacobr): make customizable by passing optional parameters to the
-  // TouchHandler constructor.
-  /**
-   * Minimum movement of touch required to be considered a drag.
-   */
-  static final _MIN_TRACKING_FOR_DRAG = 2;
-
-  /**
-   * The maximum number of ms to track a touch event. After an event is older
-   * than this value, it will be ignored in velocity calculations.
-   */
-  static final _MAX_TRACKING_TIME = 250;
-
-  /** The maximum number of touches to track. */
-  static final _MAX_TRACKING_TOUCHES = 5;
-
-  /**
-   * The maximum velocity to return, in pixels per millisecond, that is used to
-   * guard against errors in calculating end velocity of a drag. This is a very
-   * fast drag velocity.
-   */
-  static final _MAXIMUM_VELOCITY = 5;
-
-  /**
-   * The velocity to return, in pixel per millisecond, when the time stamps on
-   * the events are erroneous. The browser can return bad time stamps if the
-   * thread is blocked for the duration of the drag. This is a low velocity to
-   * prevent the content from moving quickly after a slow drag. It is less
-   * jarring if the content moves slowly after a fast drag.
-   */
-  static final _VELOCITY_FOR_INCORRECT_EVENTS = 1;
-
-  Draggable _draggable;
-  bool _tracking;
-  bool _dragging;
-  bool _touching;
-  int _startTouchX;
-  int _startTouchY;
-  int _startTime;
-  TouchEvent _lastEvent;
-  int _lastTouchX;
-  int _lastTouchY;
-  int _lastMoveX;
-  int _lastMoveY;
-  int _endTime;
-  int _endTouchX;
-  int _endTouchY;
-
-  TouchHandler(Touchable touchable, [Element element = null])
-      : _touchable = touchable,
-        _totalMoveY = 0,
-        _totalMoveX = 0,
-        _recentTouchesX = new List<int>(),
-        _recentTouchesY = new List<int>(),
-        // TODO(jmesserly): I don't like having to initialize all booleans here
-        // See b/5045736
-        _dragging = false,
-        _tracking = false,
-        _touching = false {
-    _element = element != null ? element : touchable.getElement();
-  }
-
-  /**
-   * Begin tracking the touchable element, it is eligible for dragging.
-   */
-  void _beginTracking() {
-    _tracking = true;
-  }
-
-  /**
-   * Stop tracking the touchable element, it is no longer dragging.
-   */
-  void _endTracking() {
-    _tracking = false;
-    _dragging = false;
-    _totalMoveY = 0;
-    _totalMoveX = 0;
-  }
-
-  /**
-   * Correct erroneous velocities by capping the velocity if we think it's too
-   * high, or setting it to a default velocity if know that the event data is
-   * bad. Returns the corrected velocity.
-   */
-  num _correctVelocity(num velocity) {
-    num absVelocity = velocity.abs();
-    if (absVelocity > _MAXIMUM_VELOCITY) {
-      absVelocity = _recentTouchesY.length < 6 ?
-          _VELOCITY_FOR_INCORRECT_EVENTS : _MAXIMUM_VELOCITY;
-    }
-    return absVelocity * (velocity < 0 ? -1 : 1);
-  }
-
-  /**
-   * Start listenting for events.
-   * If [capture] is True the TouchHandler should listen during the capture
-   * phase.
-   */
-  void enable([bool capture = false]) {
-    Function onEnd = (e) { _onEnd(e.timeStamp, e); };
-    _addEventListeners(
-        _element,
-        (e) { _onStart(e); },
-        (e) { _onMove(e); }, onEnd, onEnd, capture);
-  }
-
-  /**
-   * Get the current horizontal drag delta. Drag delta is defined as the deltaX
-   * of the start touch position and the last touch position.
-   */
-  int getDragDeltaX() {
-    return _lastTouchX - _startTouchX;
-  }
-
-  /**
-   * Get the current vertical drag delta. Drag delta is defined as the deltaY of
-   * the start touch position and the last touch position.
-   */
-  int getDragDeltaY() {
-    return _lastTouchY - _startTouchY;
-  }
-
-  /**
-   * Get end velocity of the drag. This method is specific to drag behavior, so
-   * if touch behavior and drag behavior is split then this should go with drag
-   * behavior. End velocity is defined as deltaXY / deltaTime where deltaXY is
-   * the difference between endPosition and the oldest recent position, and
-   * deltaTime is the difference between endTime and the oldest recent time
-   * stamp.
-   */
-  Coordinate getEndVelocity() {
-    num velocityX = 0;
-    num velocityY = 0;
-
-    if (_recentTouchesX.length > 0) {
-      num timeDeltaX = Math.max(1, _endTime - _recentTouchesX[1]);
-      velocityX = (_endTouchX - _recentTouchesX[0]) / timeDeltaX;
-    }
-
-    if (_recentTouchesY.length > 0) {
-      num timeDeltaY = Math.max(1, _endTime - _recentTouchesY[1]);
-      velocityY = (_endTouchY - _recentTouchesY[0]) / timeDeltaY;
-    }
-    velocityX = _correctVelocity(velocityX);
-    velocityY = _correctVelocity(velocityY);
-    return new Coordinate(velocityX, velocityY);
-  }
-
-  /**
-   * Return the touch of the last event.
-   */
-  Touch _getLastTouch() {
-    assert (_lastEvent != null); // Last event not set
-    return _lastEvent.touches[0];
-  }
-
-  /**
-   * Is the touch manager currently tracking touch moves to detect a drag?
-   */
-  bool isTracking() {
-    return _tracking;
-  }
-
-  /**
-   * Touch end handler.
-   */
-  void _onEnd(int timeStamp, [TouchEvent e = null]) {
-    _touching = false;
-    _touchable.onTouchEnd();
-    if (!_tracking || _draggable === null) {
-      return;
-    }
-    Touch touch = _getLastTouch();
-    int clientX = touch.clientX;
-    int clientY = touch.clientY;
-    if (_dragging) {
-      _endTime = timeStamp;
-      _endTouchX = clientX;
-      _endTouchY = clientY;
-      _recentTouchesX = _removeOldTouches(_recentTouchesX, timeStamp);
-      _recentTouchesY = _removeOldTouches(_recentTouchesY, timeStamp);
-      _draggable.onDragEnd();
-      if (e !== null) {
-        e.preventDefault();
-      }
-      ClickBuster.preventGhostClick(_startTouchX, _startTouchY);
-    }
-    _endTracking();
-  }
-
-  /**
-   * Touch move handler.
-   */
-  void _onMove(TouchEvent e) {
-    if (!_tracking || _draggable === null) {
-      return;
-    }
-    final touch = e.touches[0];
-    int clientX = touch.clientX;
-    int clientY = touch.clientY;
-    int moveX = _lastTouchX - clientX;
-    int moveY = _lastTouchY - clientY;
-    _totalMoveX += moveX.abs();
-    _totalMoveY += moveY.abs();
-    _lastTouchX = clientX;
-    _lastTouchY = clientY;
-    if (!_dragging &&
-        ((_totalMoveY > _MIN_TRACKING_FOR_DRAG && _draggable.verticalEnabled) ||
-         (_totalMoveX > _MIN_TRACKING_FOR_DRAG &&
-          _draggable.horizontalEnabled))) {
-      _dragging = _draggable.onDragStart(e);
-      if (!_dragging) {
-        _endTracking();
-      } else {
-        _startTouchX = clientX;
-        _startTouchY = clientY;
-        _startTime = e.timeStamp;
-      }
-    }
-    if (_dragging) {
-      _draggable.onDragMove();
-      _lastEvent = e;
-      e.preventDefault();
-      _recentTouchesX =
-          _removeTouchesInWrongDirection(_recentTouchesX, _lastMoveX, moveX);
-      _recentTouchesY =
-          _removeTouchesInWrongDirection(_recentTouchesY, _lastMoveY, moveY);
-      _recentTouchesX = _removeOldTouches(_recentTouchesX, e.timeStamp);
-      _recentTouchesY = _removeOldTouches(_recentTouchesY, e.timeStamp);
-      _recentTouchesX.add(clientX);
-      _recentTouchesX.add(e.timeStamp);
-      _recentTouchesY.add(clientY);
-      _recentTouchesY.add(e.timeStamp);
-    }
-    _lastMoveX = moveX;
-    _lastMoveY = moveY;
-  }
-
-  /**
-   * Touch start handler.
-   */
-  void _onStart(TouchEvent e) {
-    if (_touching) {
-      return;
-    }
-    _touching = true;
-    if (!_touchable.onTouchStart(e) || _draggable === null) {
-      return;
-    }
-    final touch = e.touches[0];
-    _startTouchX = _lastTouchX = touch.clientX;
-    _startTouchY = _lastTouchY = touch.clientY;
-    _startTime = e.timeStamp;
-    // TODO(jacobr): why don't we just clear the lists?
-    _recentTouchesX = new List<int>();
-    _recentTouchesY = new List<int>();
-    _recentTouchesX.add(touch.clientX);
-    _recentTouchesX.add(e.timeStamp);
-    _recentTouchesY.add(touch.clientY);
-    _recentTouchesY.add(e.timeStamp);
-    _lastEvent = e;
-    _beginTracking();
-  }
-
-  /**
-   * Filters the provided recent touches list to remove all touches older than
-   * the max tracking time or the 5th most recent touch.
-   * [recentTouches] specifies a list of tuples where the first item is the x
-   * or y component of the recent touch and the second item is the touch time
-   * stamp. The time of the most recent event is specified by [recentTime].
-   */
-  List<int> _removeOldTouches(List<int> recentTouches,
-                         int recentTime) {
-    int count = 0;
-    final len = recentTouches.length;
-    assert (len % 2 == 0);
-    while (count < len &&
-           recentTime - recentTouches[count + 1] > _MAX_TRACKING_TIME ||
-           (len - count) > _MAX_TRACKING_TOUCHES * 2) {
-      count += 2;
-    }
-    return count == 0 ? recentTouches : _removeFirstN(recentTouches, count);
-  }
-
-  static List<int> _removeFirstN(List<int> list, int n) {
-    return list.getRange(n, list.length - n);
-  }
-
-  /**
-   * Filters the provided recent touches list to remove all touches except the
-   * last if the move direction has changed.
-   * [recentTouches] specifies a list of tuples where the first item is the x
-   * or y component of the recent touch and the second item is the touch time
-   * stamp. The x or y component of the most recent move is specified by
-   * [recentMove].
-   */
-  List<int> _removeTouchesInWrongDirection(List<int> recentTouches,
-                                            int lastMove, int recentMove) {
-    if (lastMove !=0 && recentMove != 0 && recentTouches.length > 2 &&
-        _xor(lastMove > 0, recentMove > 0)) {
-      return _removeFirstN(recentTouches, recentTouches.length - 2);
-    }
-    return recentTouches;
-  }
-
-  // TODO(jacobr): why doesn't bool implement the xor operator directly?
-  static bool _xor(bool a, bool b) {
-    return (a === true || b === true) && !(a === true && b === true);
-  }
-
-  /**
-   * Reset the touchable element.
-   */
-  void reset() {
-    _endTracking();
-    _touching = false;
-  }
-
-  /**
-   * Call this method to enable drag behavior on a draggable delegate.
-   * The [draggable] object can be the same as the [_touchable] object, they are
-   * assigned to different members to allow for strong typing with interfaces.
-   */
-  void setDraggable(Draggable draggable) {
-    _draggable = draggable;
-  }
-}