Modern-ify KeyEvent handling.

tools/dom/src/KeyboardEventStream.dart

+// Copyright (c) 2012, 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.
+
+part of html;
+
+/**
+ * Internal class that does the actual calculations to determine keyCode and
+ * charCode for keydown, keypress, and keyup events for all browsers.
+ */
+class _KeyboardEventHandler implements EventStreamProvider<KeyEvent> {
+  // This code inspired by Closure's KeyHandling library.
+  // http://closure-library.googlecode.com/svn/docs/closure_goog_events_keyhandler.js.source.html
+
+  /**
+   * The set of keys that have been pressed down without seeing their
+   * corresponding keyup event.
+   */
+  List<KeyboardEvent> _keyDownList;
+
+  /** The set of functions that wish to be notified when a KeyEvent happens. */
+  List<Function> _callbacks;
+
+  /** The type of KeyEvent we are tracking (keyup, keydown, keypress). */
+  String _type;
+
+  /** The element we are watching for events to happen on. */
+  EventTarget _target;
+
+  // The distance to shift from upper case alphabet Roman letters to lower case.
+  final int _ROMAN_ALPHABET_OFFSET = "a".codeUnits[0] - "A".codeUnits[0];
+
+  /** Controller to produce KeyEvents for the stream. */
+  StreamController _controller;
+
+  /**
+   * An enumeration of key identifiers currently part of the W3C draft for DOM3
+   * and their mappings to keyCodes.
+   * http://www.w3.org/TR/DOM-Level-3-Events/keyset.html#KeySet-Set
+   */
+  static Map<String, int> _keyIdentifier = {
+    'Up': KeyCode.UP,
+    'Down': KeyCode.DOWN,
+    'Left': KeyCode.LEFT,
+    'Right': KeyCode.RIGHT,
+    'Enter': KeyCode.ENTER,
+    'F1': KeyCode.F1,
+    'F2': KeyCode.F2,
+    'F3': KeyCode.F3,
+    'F4': KeyCode.F4,
+    'F5': KeyCode.F5,
+    'F6': KeyCode.F6,
+    'F7': KeyCode.F7,
+    'F8': KeyCode.F8,
+    'F9': KeyCode.F9,
+    'F10': KeyCode.F10,
+    'F11': KeyCode.F11,
+    'F12': KeyCode.F12,
+    'U+007F': KeyCode.DELETE,
+    'Home': KeyCode.HOME,
+    'End': KeyCode.END,
+    'PageUp': KeyCode.PAGE_UP,
+    'PageDown': KeyCode.PAGE_DOWN,
+    'Insert': KeyCode.INSERT
+  };
+
+  /**
+   * Gets the type of the event which this would listen for on the specified
+   * event target.
+   */
+  String getEventType(EventTarget target) => 'KeyEvent';
+
+  /** Return a stream for KeyEvents for the specified target. */
+  Stream<KeyEvent> forTarget(EventTarget e, {bool useCapture: false}) {
+    _initializeAllEventListeners(e);
+    return _controller.stream;
+  }
+
+  /**
+   * General constructor, performs basic initialization for our improved
+   * KeyboardEvent controller.
+   */
+  _KeyboardEventHandler(String type) {
+    _type = type;
+    _controller = new StreamController.broadcast();
+    _callbacks = [];
+  }
+
+  /**
+   * Hook up all event listeners under the covers so we can estimate keycodes
+   * and charcodes when they are not provided.
+   */
+  _initializeAllEventListeners(EventTarget target) {
+    _target = target;
+    _keyDownList = [];
+    Element.keyDownEvent.forTarget(_target, useCapture: true).listen(
+        processKeyDown);
+    Element.keyPressEvent.forTarget(_target, useCapture: true).listen(
+        processKeyPress);
+    Element.keyUpEvent.forTarget(_target, useCapture: true).listen(
+        processKeyUp);
+  }
+
+  /**
+   * Notify all callback listeners that a KeyEvent of the relevant type has
+   * occurred.
+   */
+  bool _dispatch(KeyEvent event) {
+    if (event.type == _type)
+      _controller.add(event);
+  }
+
+  /** Determine if caps lock is one of the currently depressed keys. */
+  bool get _capsLockOn =>
+      _keyDownList.any((var element) => element.keyCode == KeyCode.CAPS_LOCK);
+
+  /**
+   * Given the previously recorded keydown key codes, see if we can determine
+   * the keycode of this keypress [event]. (Generally browsers only provide
+   * charCode information for keypress events, but with a little
+   * reverse-engineering, we can also determine the keyCode.) Returns
+   * KeyCode.UNKNOWN if the keycode could not be determined.
+   */
+  int _determineKeyCodeForKeypress(KeyboardEvent event) {
+    // Note: This function is a work in progress. We'll expand this function
+    // once we get more information about other keyboards.
+    for (var prevEvent in _keyDownList) {
+      if (prevEvent._shadowCharCode == event.charCode) {
+        return prevEvent.keyCode;
+      }
+      if ((event.shiftKey || _capsLockOn) && event.charCode >= "A".codeUnits[0]
+          && event.charCode <= "Z".codeUnits[0] && event.charCode +
+          _ROMAN_ALPHABET_OFFSET == prevEvent._shadowCharCode) {
+        return prevEvent.keyCode;
+      }
+    }
+    return KeyCode.UNKNOWN;
+  }
+
+  /**
+   * Given the charater code returned from a keyDown [event], try to ascertain
+   * and return the corresponding charCode for the character that was pressed.
+   * This information is not shown to the user, but used to help polyfill
+   * keypress events.
+   */
+  int _findCharCodeKeyDown(KeyboardEvent event) {
+    if (event.keyLocation == 3) { // Numpad keys.
+      switch (event.keyCode) {
+        case KeyCode.NUM_ZERO:
+          // Even though this function returns _charCodes_, for some cases the
+          // KeyCode == the charCode we want, in which case we use the keycode
+          // constant for readability.
+          return KeyCode.ZERO;
+        case KeyCode.NUM_ONE:
+          return KeyCode.ONE;
+        case KeyCode.NUM_TWO:
+          return KeyCode.TWO;
+        case KeyCode.NUM_THREE:
+          return KeyCode.THREE;
+        case KeyCode.NUM_FOUR:
+          return KeyCode.FOUR;
+        case KeyCode.NUM_FIVE:
+          return KeyCode.FIVE;
+        case KeyCode.NUM_SIX:
+          return KeyCode.SIX;
+        case KeyCode.NUM_SEVEN:
+          return KeyCode.SEVEN;
+        case KeyCode.NUM_EIGHT:
+          return KeyCode.EIGHT;
+        case KeyCode.NUM_NINE:
+          return KeyCode.NINE;
+        case KeyCode.NUM_MULTIPLY:
+          return 42; // Char code for *
+        case KeyCode.NUM_PLUS:
+          return 43; // +
+        case KeyCode.NUM_MINUS:
+          return 45; // -
+        case KeyCode.NUM_PERIOD:
+          return 46; // .
+        case KeyCode.NUM_DIVISION:
+          return 47; // /
+      }
+    } else if (event.keyCode >= 65 && event.keyCode <= 90) {
+      // Set the "char code" for key down as the lower case letter. Again, this
+      // will not show up for the user, but will be helpful in estimating
+      // keyCode locations and other information during the keyPress event.
+      return event.keyCode + _ROMAN_ALPHABET_OFFSET;
+    }
+    switch(event.keyCode) {
+      case KeyCode.SEMICOLON:
+        return KeyCode.FF_SEMICOLON;
+      case KeyCode.EQUALS:
+        return KeyCode.FF_EQUALS;
+      case KeyCode.COMMA:
+        return 44; // Ascii value for ,
+      case KeyCode.DASH:
+        return 45; // -
+      case KeyCode.PERIOD:
+        return 46; // .
+      case KeyCode.SLASH:
+        return 47; // /
+      case KeyCode.APOSTROPHE:
+        return 96; // `
+      case KeyCode.OPEN_SQUARE_BRACKET:
+        return 91; // [
+      case KeyCode.BACKSLASH:
+        return 92; // \
+      case KeyCode.CLOSE_SQUARE_BRACKET:
+        return 93; // ]
+      case KeyCode.SINGLE_QUOTE:
+        return 39; // '
+    }
+    return event.keyCode;
+  }
+
+  /**
+   * Returns true if the key fires a keypress event in the current browser.
+   */
+  bool _firesKeyPressEvent(KeyEvent event) {
+    if (!Device.isIE && !Device.isWebKit) {
+      return true;
+    }
+
+    if (Device.userAgent.contains('Mac') && event.altKey) {
+      return KeyCode.isCharacterKey(event.keyCode);
+    }
+
+    // Alt but not AltGr which is represented as Alt+Ctrl.
+    if (event.altKey && !event.ctrlKey) {
+      return false;
+    }
+
+    // Saves Ctrl or Alt + key for IE and WebKit, which won't fire keypress.
+    if (!event.shiftKey &&
+        (_keyDownList.last.keyCode == KeyCode.CTRL ||
+         _keyDownList.last.keyCode == KeyCode.ALT ||
+         Device.userAgent.contains('Mac') &&
+         _keyDownList.last.keyCode == KeyCode.META)) {
+      return false;
+    }
+
+    // Some keys with Ctrl/Shift do not issue keypress in WebKit.
+    if (Device.isWebKit && event.ctrlKey && event.shiftKey && (
+        event.keyCode == KeyCode.BACKSLASH ||
+        event.keyCode == KeyCode.OPEN_SQUARE_BRACKET ||
+        event.keyCode == KeyCode.CLOSE_SQUARE_BRACKET ||
+        event.keyCode == KeyCode.TILDE ||
+        event.keyCode == KeyCode.SEMICOLON || event.keyCode == KeyCode.DASH ||
+        event.keyCode == KeyCode.EQUALS || event.keyCode == KeyCode.COMMA ||
+        event.keyCode == KeyCode.PERIOD || event.keyCode == KeyCode.SLASH ||
+        event.keyCode == KeyCode.APOSTROPHE ||
+        event.keyCode == KeyCode.SINGLE_QUOTE)) {
+      return false;
+    }
+
+    switch (event.keyCode) {
+      case KeyCode.ENTER:
+        // IE9 does not fire keypress on ENTER.
+        return !Device.isIE;
+      case KeyCode.ESC:
+        return !Device.isWebKit;
+    }
+
+    return KeyCode.isCharacterKey(event.keyCode);
+  }
+
+  /**
+   * Normalize the keycodes to the IE KeyCodes (this is what Chrome, IE, and
+   * Opera all use).
+   */
+  int _normalizeKeyCodes(KeyboardEvent event) {
+    // Note: This may change once we get input about non-US keyboards.
+    if (Device.isFirefox) {
+      switch(event.keyCode) {
+        case KeyCode.FF_EQUALS:
+          return KeyCode.EQUALS;
+        case KeyCode.FF_SEMICOLON:
+          return KeyCode.SEMICOLON;
+        case KeyCode.MAC_FF_META:
+          return KeyCode.META;
+        case KeyCode.WIN_KEY_FF_LINUX:
+          return KeyCode.WIN_KEY;
+      }
+    }
+    return event.keyCode;
+  }
+
+  /** Handle keydown events. */
+  void processKeyDown(KeyboardEvent e) {
+    // Ctrl-Tab and Alt-Tab can cause the focus to be moved to another window
+    // before we've caught a key-up event.  If the last-key was one of these
+    // we reset the state.
+    if (_keyDownList.length > 0 &&
+        (_keyDownList.last.keyCode == KeyCode.CTRL && !e.ctrlKey ||
+         _keyDownList.last.keyCode == KeyCode.ALT && !e.altKey ||
+         Device.userAgent.contains('Mac') &&
+         _keyDownList.last.keyCode == KeyCode.META && !e.metaKey)) {
+      _keyDownList = [];
+    }
+
+    var event = new KeyEvent(e);
+    event._shadowKeyCode = _normalizeKeyCodes(event);
+    // Technically a "keydown" event doesn't have a charCode. This is
+    // calculated nonetheless to provide us with more information in giving
+    // as much information as possible on keypress about keycode and also
+    // charCode.
+    event._shadowCharCode = _findCharCodeKeyDown(event);
+    if (_keyDownList.length > 0 && event.keyCode != _keyDownList.last.keyCode &&
+        !_firesKeyPressEvent(event)) {
+      // Some browsers have quirks not firing keypress events where all other
+      // browsers do. This makes them more consistent.
+      processKeyPress(event);
+    }
+    _keyDownList.add(event);
+    _dispatch(event);
+  }
+
+  /** Handle keypress events. */
+  void processKeyPress(KeyboardEvent event) {
+    var e = new KeyEvent(event);
+    // IE reports the character code in the keyCode field for keypress events.
+    // There are two exceptions however, Enter and Escape.
+    if (Device.isIE) {
+      if (e.keyCode == KeyCode.ENTER || e.keyCode == KeyCode.ESC) {
+        e._shadowCharCode = 0;
+      } else {
+        e._shadowCharCode = e.keyCode;
+      }
+    } else if (Device.isOpera) {
+      // Opera reports the character code in the keyCode field.
+      e._shadowCharCode = KeyCode.isCharacterKey(e.keyCode) ? e.keyCode : 0;
+    }
+    // Now we guestimate about what the keycode is that was actually
+    // pressed, given previous keydown information.
+    e._shadowKeyCode = _determineKeyCodeForKeypress(e);
+
+    // Correct the key value for certain browser-specific quirks.
+    if (e._shadowKeyIdentifier != null &&
+        _keyIdentifier.containsKey(e._shadowKeyIdentifier)) {
+      // This is needed for Safari Windows because it currently doesn't give a
+      // keyCode/which for non printable keys.
+      e._shadowKeyCode = _keyIdentifier[e._shadowKeyIdentifier];
+    }
+    e._shadowAltKey = _keyDownList.any((var element) => element.altKey);
+    _dispatch(e);
+  }
+
+  /** Handle keyup events. */
+  void processKeyUp(KeyboardEvent event) {
+    var e = new KeyEvent(event);
+    KeyboardEvent toRemove = null;
+    for (var key in _keyDownList) {
+      if (key.keyCode == e.keyCode) {
+        toRemove = key;
+      }
+    }
+    if (toRemove != null) {
+      _keyDownList =
+          _keyDownList.where((element) => element != toRemove).toList();
+    } else if (_keyDownList.length > 0) {
+      // This happens when we've reached some international keyboard case we
+      // haven't accounted for or we haven't correctly eliminated all browser
+      // inconsistencies. Filing bugs on when this is reached is welcome!
+      _keyDownList.removeLast();
+    }
+    _dispatch(e);
+  }
+}
+
+
+/**
+ * Records KeyboardEvents that occur on a particular element, and provides a
+ * stream of outgoing KeyEvents with cross-browser consistent keyCode and
+ * charCode values despite the fact that a multitude of browsers that have
+ * varying keyboard default behavior.
+ *
+ * Example usage:
+ *
+ *     new KeyboardEventStream.onKeyDown(document.body).listen(
+ *         keydownHandlerTest);
+ *
+ * This class is very much a work in progress, and we'd love to get information
+ * on how we can make this class work with as many international keyboards as
+ * possible. Bugs welcome!
+ */
+class KeyboardEventStream implements Stream<KeyEvent> {
+  _KeyboardEventHandler _handler;
+  Stream<KeyEvent> _stream;
+
+  /** Named constructor to produce a stream for onKeyPress events. */
+  KeyboardEventStream.onKeyPress(EventTarget target) {
+    _handler = new _KeyboardEventHandler('keypress');
+    _stream = _handler.forTarget(target);
+  }
+
+  /** Named constructor to produce a stream for onKeyUp events. */
+  KeyboardEventStream.onKeyUp(EventTarget target) {
+    _handler = new _KeyboardEventHandler('keyup');
+    _stream = _handler.forTarget(target);
+  }
+
+  /** Named constructor to produce a stream for onKeyDown events. */
+  KeyboardEventStream.onKeyDown(EventTarget target) {
+    _handler = new _KeyboardEventHandler('keydown');
+    _stream = _handler.forTarget(target);
+  }
+
+  /**
+   * Unlike regular KeyboardEvents, you can programmatically add KeyEvents to
+   * this stream. Be careful, though! If you add a keyDown event without a
+   * corresponding keyUp event later, the stream may have difficulty estimating
+   * future key codes.
+   */
+  void addKeyDown(KeyEvent e) {
+    _handler.processKeyDown(e);
+  }
+
+  /**
+   * Unlike regular KeyboardEvents, you can programmatically add KeyEvents to
+   * this stream. Be careful, though! If you add a keyUp event without a
+   * corresponding keyDown event previously, the stream may have difficulty
+   * estimating future key codes.
+   */
+  void addKeyUp(KeyEvent e) {
+    _handler.processKeyUp(e);
+  }
+
+  /**
+   * Unlike regular KeyboardEvents, you can programmatically add KeyEvents to
+   * this stream.
+   */
+  void addKeyPress(KeyEvent e) {
+    _handler.processKeyPress(e);
+  }
+
+  // ---------------- Stream implementation methods: ---------------
+  /**
+   * Adds a subscription to this stream.
+   *
+   * On each data event from this stream, the subscriber's [onData] handler
+   * is called. If [onData] is null, nothing happens.
+   *
+   * On errors from this stream, the [onError] handler is given a
+   * [AsyncError] object describing the error.
+   *
+   * If this stream closes, the [onDone] handler is called.
+   *
+   * If [unsubscribeOnError] is true, the subscription is ended when
+   * the first error is reported. The default is false.
+   */
+  StreamSubscription<KeyEvent> listen(void onData(KeyEvent event),
+      {void onError(AsyncError error), void onDone(),
+      bool unsubscribeOnError}) => _stream.listen(onData, onError:
+      onError, onDone: onDone, unsubscribeOnError: unsubscribeOnError);
+
+  /**
+   * Reports whether this stream is a broadcast stream.
+   */
+  bool get isBroadcast => _stream.isBroadcast;
+
+  /** Counts the elements in the stream. */
+  Future<int> get length => _stream.length;
+
+  /** Reports whether this stream contains any elements. */
+  Future<bool> get isEmpty => _stream.isEmpty;
+
+  /**
+   * Returns the first element.
+   *
+   * If [this] is empty throws a [StateError]. Otherwise this method is
+   * equivalent to [:this.elementAt(0):]
+   */
+  Future<KeyEvent> get first => _stream.first;
+
+  /**
+   * Returns the last element.
+   *
+   * If [this] is empty throws a [StateError].
+   */
+  Future<KeyEvent> get last => _stream.last;
+
+  /**
+   * Returns the single element.
+   *
+   * If [this] is empty or has more than one element throws a [StateError].
+   */
+  Future<KeyEvent> get single => _stream.single;
+
+  /**
+   * Creates a new stream from this stream that converts each element
+   * into zero or more events.
+   *
+   * Each incoming event is converted to an [Iterable] of new events,
+   * and each of these new events are then sent by the returned stream
+   * in order.
+   */
+  Stream<dynamic> expand(Iterable convert(KeyEvent value)) =>
+      _stream.expand(convert);
+
+  /**
+   * Chains this stream as the input of the provided [StreamTransformer].
+   *
+   * Returns the result of [:streamTransformer.bind:] itself.
+   */
+  Stream<dynamic> transform(StreamTransformer<KeyEvent, dynamic>
+      streamTransformer) => _stream.transform(streamTransformer);
+
+  /**
+   * Checks whether [test] accepts any element provided by this stream.
+   *
+   * Completes the [Future] when the answer is known.
+   * If this stream reports an error, the [Future] will report that error.
+   */
+  Future<bool> any(bool test(KeyEvent element)) => _stream.any(test);
+
+  /**
+   * Returns a multi-subscription stream that produces the same events as this.
+   *
+   * If this stream is single-subscription, return a new stream that allows
+   * multiple subscribers. It will subscribe to this stream when its first
+   * subscriber is added, and unsubscribe again when the last subscription is
+   * cancelled.
+   *
+   * If this stream is already a broadcast stream, it is returned unmodified.
+   */
+  Stream<KeyEvent> asBroadcastStream() => _stream;
+
+  /**
+   * Checks whether [match] occurs in the elements provided by this stream.
+   *
+   * Completes the [Future] when the answer is known.
+   * If this stream reports an error, the [Future] will report that error.
+   */
+  Future<bool> contains(KeyEvent match) => _stream.contains(match);
+
+  /**
+   * Skips data events if they are equal to the previous data event.
+   *
+   * The returned stream provides the same events as this stream, except
+   * that it never provides two consequtive data events that are equal.
+   *
+   * Equality is determined by the provided [equals] method. If that is
+   * omitted, the '==' operator on the last provided data element is used.
+   */
+  Stream<KeyEvent> distinct([bool equals(KeyEvent previous, KeyEvent next)]) =>
+      _stream.distinct(equals);
+
+   /**
+    * Returns the value of the [index]th data event of this stream.
+    *
+    * If an error event occurs, the future will end with this error.
+    *
+    * If this stream provides fewer than [index] elements before closing,
+    * an error is reported.
+    */
+  Future<KeyEvent> elementAt(int index) => _stream.elementAt(index);
+
+  /**
+   * Checks whether [test] accepts all elements provided by this stream.
+   *
+   * Completes the [Future] when the answer is known.
+   * If this stream reports an error, the [Future] will report that error.
+   */
+  Future<bool> every(bool test(KeyEvent element)) =>
+      _stream.every(test);
+
+  /**
+   * Finds the first element of this stream matching [test].
+   *
+   * Returns a future that is filled with the first element of this stream
+   * that [test] returns true for.
+   *
+   * If no such element is found before this stream is done, and a
+   * [defaultValue] function is provided, the result of calling [defaultValue]
+   * becomes the value of the future.
+   *
+   * If an error occurs, or if this stream ends without finding a match and
+   * with no [defaultValue] function provided, the future will receive an
+   * error.
+   */
+  Future<KeyEvent> firstWhere(bool test(KeyEvent value),
+      {KeyEvent defaultValue()}) => _stream.firstWhere(test);
+
+  /**
+   * Creates a wrapper Stream that intercepts some errors from this stream.
+   *
+   * If this stream sends an error that matches [test], then it is intercepted
+   * by the [handle] function.
+   *
+   * An [AsyncError] [:e:] is matched by a test function if [:test(e):] returns
+   * true. If [test] is omitted, every error is considered matching.
+   *
+   * If the error is intercepted, the [handle] function can decide what to do
+   * with it. It can throw if it wants to raise a new (or the same) error,
+   * or simply return to make the stream forget the error.
+   *
+   * If you need to transform an error into a data event, use the more generic
+   * [Stream.transformEvent] to handle the event by writing a data event to
+   * the output sink
+   */
+  Stream<KeyEvent> handleError(void handle(AsyncError error),
+      {bool test(error)}) => _stream.handleError(handle);
+
+  /**
+   * Finds the last element in this stream matching [test].
+   *
+   * As [firstWhere], except that the last matching element is found.
+   * That means that the result cannot be provided before this stream
+   * is done.
+   */
+  Future<KeyEvent> lastWhere(bool test(KeyEvent value),
+      {KeyEvent defaultValue()}) => _stream.lastWhere(test);
+
+  /**
+   * Creates a new stream that converts each element of this stream
+   * to a new value using the [convert] function.
+   */
+  Stream map(convert(KeyEvent event)) => _stream.map(convert);
+
+  /**
+   * Finds the largest element in the stream.
+   *
+   * If the stream is empty, the result is [:null:].
+   * Otherwise the result is an value from the stream that is not smaller
+   * than any other value from the stream (according to [compare], which must
+   * be a [Comparator]).
+   *
+   * If [compare] is omitted, it defaults to [Comparable.compare].
+   *
+   * *Deprecated*. Use [reduce] with a binary max method if needed.
+   */
+  Future<KeyEvent> max([int compare(KeyEvent a, KeyEvent b)]) =>
+      _stream.max(compare);
+
+  /**
+   * Finds the least element in the stream.
+   *
+   * If the stream is empty, the result is [:null:].
+   * Otherwise the result is a value from the stream that is not greater
+   * than any other value from the stream (according to [compare], which must
+   * be a [Comparator]).
+   *
+   * If [compare] is omitted, it defaults to [Comparable.compare].
+   *
+   * *Deprecated*. Use [reduce] with a binary min method if needed.
+   */
+  Future<KeyEvent> min([int compare(KeyEvent a, KeyEvent b)]) =>
+      _stream.min(compare);
+
+  /**
+   * Binds this stream as the input of the provided [StreamConsumer].
+   */
+  Future pipe(StreamConsumer<KeyEvent, dynamic> streamConsumer) =>
+      _stream.pipe(streamConsumer);
+
+  Future pipeInto(EventSink<KeyEvent> sink, {void onError(AsyncError error),
+      bool unsubscribeOnError}) => _stream.pipeInto(sink, onError:
+      onError, unsubscribeOnError: unsubscribeOnError);
+
+  /** Reduces a sequence of values by repeatedly applying [combine]. */
+  Future reduce(initialValue, combine(previous, KeyEvent element)) =>
+      _stream.reduce(initialValue, combine);
+
+  /**
+   * Finds the single element in this stream matching [test].
+   *
+   * Like [lastMatch], except that it is an error if more than one
+   * matching element occurs in the stream.
+   */
+  Future<KeyEvent> singleWhere(bool test(KeyEvent value)) =>
+    _stream.singleWhere(test);
+
+  /**
+   * Skips the first [count] data events from this stream.
+   */
+  Stream<KeyEvent> skip(int count) => _stream.skip(count);
+
+  /**
+   * Skip data events from this stream while they are matched by [test].
+   *
+   * Error and done events are provided by the returned stream unmodified.
+   *
+   * Starting with the first data event where [test] returns true for the
+   * event data, the returned stream will have the same events as this stream.
+   */
+  Stream<KeyEvent> skipWhile(bool test(KeyEvent value)) =>
+      _stream.skipWhile(test);
+
+  /**
+   * Provides at most the first [n] values of this stream.
+   *
+   * Forwards the first [n] data events of this stream, and all error
+   * events, to the returned stream, and ends with a done event.
+   *
+   * If this stream produces fewer than [count] values before it's done,
+   * so will the returned stream.
+   */
+  Stream<KeyEvent> take(int count) => _stream.take(count);
+
+  /**
+   * Forwards data events while [test] is successful.
+   *
+   * The returned stream provides the same events as this stream as long
+   * as [test] returns [:true:] for the event data. The stream is done
+   * when either this stream is done, or when this stream first provides
+   * a value that [test] doesn't accept.
+   */
+  Stream<KeyEvent> takeWhile(bool test(KeyEvent value)) =>
+      _stream.takeWhile(test);
+
+  /** Collects the data of this stream in a [List]. */
+  Future<List<KeyEvent>> toList() => _stream.toList();
+
+  /** Collects the data of this stream in a [Set]. */
+  Future<Set<KeyEvent>> toSet() => _stream.toSet();
+
+  /**
+   * Creates a new stream from this stream that discards some data events.
+   *
+   * The new stream sends the same error and done events as this stream,
+   * but it only sends the data events that satisfy the [test].
+   */
+  Stream<KeyEvent> where(bool test(KeyEvent event)) =>
+      _stream.where(test);
+}