Add flutter_web samples (#75)

web/charts/flutter/lib/src/behaviors/a11y/domain_a11y_explore_behavior.dart

@@ -0,0 +1,112 @@
+// Copyright 2018 the Charts project authors. Please see the AUTHORS file
+// for details.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:charts_common/common.dart' as common
+    show DomainA11yExploreBehavior, VocalizationCallback, ExploreModeTrigger;
+import 'package:flutter_web/widgets.dart' show hashValues;
+import '../chart_behavior.dart' show ChartBehavior, GestureType;
+
+/// Behavior that generates semantic nodes for each domain.
+class DomainA11yExploreBehavior
+    extends ChartBehavior<common.DomainA11yExploreBehavior> {
+  /// Returns a string for a11y vocalization from a list of series datum.
+  final common.VocalizationCallback vocalizationCallback;
+
+  final Set<GestureType> desiredGestures;
+
+  /// The gesture that activates explore mode. Defaults to long press.
+  ///
+  /// Turning on explore mode asks this [A11yBehavior] to generate nodes within
+  /// this chart.
+  final common.ExploreModeTrigger exploreModeTrigger;
+
+  /// Minimum width of the bounding box for the a11y focus.
+  ///
+  /// Must be 1 or higher because invisible semantic nodes should not be added.
+  final double minimumWidth;
+
+  /// Optionally notify the OS when explore mode is enabled.
+  final String exploreModeEnabledAnnouncement;
+
+  /// Optionally notify the OS when explore mode is disabled.
+  final String exploreModeDisabledAnnouncement;
+
+  DomainA11yExploreBehavior._internal(
+      {this.vocalizationCallback,
+      this.exploreModeTrigger,
+      this.desiredGestures,
+      this.minimumWidth,
+      this.exploreModeEnabledAnnouncement,
+      this.exploreModeDisabledAnnouncement});
+
+  factory DomainA11yExploreBehavior(
+      {common.VocalizationCallback vocalizationCallback,
+      common.ExploreModeTrigger exploreModeTrigger,
+      double minimumWidth,
+      String exploreModeEnabledAnnouncement,
+      String exploreModeDisabledAnnouncement}) {
+    final desiredGestures = new Set<GestureType>();
+    exploreModeTrigger ??= common.ExploreModeTrigger.pressHold;
+
+    switch (exploreModeTrigger) {
+      case common.ExploreModeTrigger.pressHold:
+        desiredGestures..add(GestureType.onLongPress);
+        break;
+      case common.ExploreModeTrigger.tap:
+        desiredGestures..add(GestureType.onTap);
+        break;
+    }
+
+    return new DomainA11yExploreBehavior._internal(
+      vocalizationCallback: vocalizationCallback,
+      desiredGestures: desiredGestures,
+      exploreModeTrigger: exploreModeTrigger,
+      minimumWidth: minimumWidth,
+      exploreModeEnabledAnnouncement: exploreModeEnabledAnnouncement,
+      exploreModeDisabledAnnouncement: exploreModeDisabledAnnouncement,
+    );
+  }
+
+  @override
+  common.DomainA11yExploreBehavior<D> createCommonBehavior<D>() {
+    return new common.DomainA11yExploreBehavior<D>(
+        vocalizationCallback: vocalizationCallback,
+        exploreModeTrigger: exploreModeTrigger,
+        minimumWidth: minimumWidth,
+        exploreModeEnabledAnnouncement: exploreModeEnabledAnnouncement,
+        exploreModeDisabledAnnouncement: exploreModeDisabledAnnouncement);
+  }
+
+  @override
+  void updateCommonBehavior(common.DomainA11yExploreBehavior commonBehavior) {}
+
+  @override
+  String get role => 'DomainA11yExplore-${exploreModeTrigger}';
+
+  @override
+  bool operator ==(Object o) =>
+      o is DomainA11yExploreBehavior &&
+      vocalizationCallback == o.vocalizationCallback &&
+      exploreModeTrigger == o.exploreModeTrigger &&
+      minimumWidth == o.minimumWidth &&
+      exploreModeEnabledAnnouncement == o.exploreModeEnabledAnnouncement &&
+      exploreModeDisabledAnnouncement == o.exploreModeDisabledAnnouncement;
+
+  @override
+  int get hashCode {
+    return hashValues(minimumWidth, vocalizationCallback, exploreModeTrigger,
+        exploreModeEnabledAnnouncement, exploreModeDisabledAnnouncement);
+  }
+}