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

client/touch/ScrollWatcher.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.
-
-interface ScrollListener {
-  /**
-   * The callback invoked for a scroll event.
-   * [decelerating] specifies whether or not the content is moving due
-   * to deceleration. It should be false if the content is moving because the
-   * user is dragging the content.
-   */
-  void onScrollerMoved(double scrollX, double scrollY, bool decelerating);
-}
-
-/**
- * The scroll watcher is intended to provide a single way to
- * listen for scroll events from instances of Scroller.
- * TODO(jacobr): this class is obsolete.
- */
-class ScrollWatcher {
-  Scroller _scroller;
-
-  List<ScrollListener> _listeners;
-
-  Element _scrollerEl;
-
-  ScrollWatcher(Scroller scroller)
-      : _scroller = scroller, _listeners = new List<ScrollListener>() {
-  }
-
-  void addListener(ScrollListener listener) {
-    _listeners.add(listener);
-  }
-
-  /**
-   * Send the scroll event to all listeners.
-   * [decelerating] is true if the offset is changing because of deceleration.
-   */
-  void _dispatchScroll(num scrollX, num scrollY,
-                       [bool decelerating = false]) {
-    for (final listener in _listeners) {
-      listener.onScrollerMoved(scrollX, scrollY, decelerating);
-    }
-  }
-
-  /**
-   * Initializes elements and event handlers. Must be called after construction
-   * and before usage.
-   */
-  void initialize() {
-    _scrollerEl = _scroller.getElement();
-    _scroller.onContentMoved.add((e) { _onContentMoved(e); });
-  }
-
-  /**
-   * This callback is invoked any time the scroller content offset changes.
-   */
-  void _onContentMoved(Event e) {
-    num scrollX = _scroller.getHorizontalOffset();
-    num scrollY = _scroller.getVerticalOffset();
-    _dispatchScroll(scrollX, scrollY);
-  }
-}