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

client/observable/EventBatch.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.
-
-/**
- * Accumulates change events from several observable objects.
- *
- * wrap() is public and used by client code.  The other methods are used by
- * AbstractObservable, which works with this class to implement batching.
- */
-class EventBatch {
-
-  /** The current active batch, if any. */
-  static EventBatch current;
-
-  /** Used to generate unique ids for observable objects. */
-  static int nextUid;
-
-  /** Map from observable object's uid to their tracked events. */
-  // TODO(sigmund): use [Observable] instead of [int] when [Map] can support it,
-  Map<int, EventSummary> summaries;
-
-  /** Whether this batch is currently firing and therefore is sealed. */
-  bool sealed = false;
-
-  /**
-   * Private constructor that shouldn't be used externally. Use [wrap] to ensure
-   * that a batch exists when running a function.
-   */
-  EventBatch._internal() : summaries = new Map<int, EventSummary>();
-
-  /**
-   * Ensure there is an event batch where [userFunction] can accumuluate events.
-   * When the batch is complete, fire all events at once.
-   */
-  static Function wrap(userFunction(var a)) {
-    return (e) {
-      if (current == null) {
-        // Not in a batch so create one.
-        final batch = new EventBatch._internal();
-        current = batch;
-        var result = null;
-        try {
-          // TODO(jmesserly): don't return here, otherwise an exception in
-          // the finally clause will cause it to rerun. See bug#5350131.
-          result = userFunction(e);
-        } finally {
-          assert(current == batch); // no one should've changed this
-          // TODO(jmesserly): VM doesn't seem to like nested try/finally, so
-          // set current to null before _notify. That will ensure we're back
-          // to the right state, even if _notify throws.
-          current = null;
-          batch._notify();
-        }
-        return result;
-      } else {
-        // Already in a batch, so just use it.
-        // TODO(rnystrom): Re-entrant calls to wrap() are kind of hairy. They
-        // can occur in at least one known place:
-        // 1. You respond to an event handler by calling a function with wrap()
-        //    (i.e. the normal way we wrap event handlers).
-        // 2. In that handler, you spawn an XHR. You give it a callback which
-        //    is also calling wrap, so that when it's later invoked, that is in
-        //    a batch too.
-        // 3. Because of an error the XHR fails and calls the callback
-        //    immediately instead of unwinding the stack past the first wrap()
-        //    and then calling it asynchronously.
-        // This check handles that, but ideally we'd have a more elegant way of
-        // notifying after a series of changes like a onEventHandlerFinished
-        // event or something built into the DOM API.
-        return userFunction(e);
-      }
-    };
-  }
-
-  /** Returns a unique global id for observable objects. */
-  static int genUid() {
-    if (nextUid == null) {
-      nextUid = 1;
-    }
-    return nextUid++;
-  }
-
-  /** Retrieves the events associated with {@code obj}. */
-  EventSummary getEvents(Observable obj) {
-    int uid = obj.uid;
-    EventSummary summary = summaries[uid];
-    if (summary == null) {
-      assert (!sealed);
-      summary = new EventSummary(obj);
-      summaries[uid] = summary;
-    }
-    return summary;
-  }
-
-  /** Fires all events at once. */
-  void _notify() {
-    assert(!sealed);
-    sealed = true;
-    for (final summary in summaries.getValues()) {
-      summary.notify();
-    }
-  }
-}