add search operation

packages/notus/lib/notus.dart

 
 export 'src/document.dart';
 export 'src/history.dart';
+export 'src/search.dart' show SearchResultEntity;
 export 'src/document/attributes.dart';
 export 'src/document/block.dart';
 export 'src/document/leaf.dart';

packages/notus/lib/src/document.dart

         // _delta = Delta()..insert('\n') {
       _history = NotusHistory(),
         _delta = Delta()..insert('\n') {
-      _searchController = NotusSearch(_delta);
+      _searchController = NotusSearch();
     _loadDocument(_delta);
   }
 
       : _heuristics = NotusHeuristics.fallback,
       _history = NotusHistory(),
         _delta = Delta.fromJson(data) {
-          _searchController = NotusSearch(_delta);
+          _searchController = NotusSearch();
     _loadDocument(_delta);
   }
 
       : assert(delta != null),
         _heuristics = NotusHeuristics.fallback,
         _history = NotusHistory(),
-        _searchController = NotusSearch(delta),
+        _searchController = NotusSearch(),
         _delta = delta {
     _loadDocument(_delta);
   }
     final notusChange = NotusChange(before, change, source);
     _controller.add(notusChange);
     if (history != true && search != true) _history?.handleDocChange(notusChange);
-    if (search != true) _searchController = NotusSearch(_delta);
+    // if (search != true) {
+    //   _searchController = NotusSearch(_delta);
+    // }
   }
 
   //
     }
   }
 
-  void search(String text) {
-    _searchController.search(this, text);
+  SearchResultEntity search(String text) {
+    return _searchController.search(this, text);
+  }
+
+  SearchResultEntity searchPrev() {
+    return _searchController.prev(this);
+  }
+
+  SearchResultEntity searchNext() {
+    return _searchController.next(this);
   }
 
   Delta undo() {

packages/notus/lib/src/document/attributes.dart

   static const line = LineAttributeBuilder._();
 
   // SearchHighLight attributes
-  static const highlight = _HighlightAttribute();
+  static const highlight = HighlightAttributeBuilder._();
 
   // Color attributes
   static const color = ColorAttributeBuilder._();
 ///
 /// There is no need to use this class directly, consider using
 /// [NotusAttribute.highlight] instead.
-class _HighlightAttribute extends NotusAttribute<bool> {
-  const _HighlightAttribute() : super._('highlight', NotusAttributeScope.inline, true);
+class HighlightAttributeBuilder extends NotusAttributeBuilder<double> {
+
+  static const _kColor = 'highlight';
+  const HighlightAttributeBuilder._()
+      : super._(_kColor, NotusAttributeScope.inline);
+
+  /// Creates a Highlight attribute with specified Highlight [value].
+  NotusAttribute<double> fromDouble(double value) =>
+      NotusAttribute<double>._(key, scope, value);
 }
 
 /// Builder for color attribute values.

packages/notus/lib/src/document/node.dart

 
   /// Offset in characters of this node in the document.
   int get documentOffset {
-    final parentOffset = (_parent is! RootNode) ? _parent.documentOffset : 0;
+    final parentOffset = (_parent is! RootNode && _parent != null) ? _parent.documentOffset : 0;
     return parentOffset + offset;
   }
 

packages/notus/lib/src/search.dart

 /// used for redo or undo function
 ///
 class NotusSearch {
-  const NotusSearch(this.delta);
-  final Delta delta;
+  
+  Delta undoDelta;
+  List<RegExpMatch> _result = [];
+  SearchResultEntity _entity = const SearchResultEntity();
 
-  void search(NotusDocument doc, String text) {
-    doc.compose(delta, ChangeSource.remote, search: true);
+  SearchResultEntity search(NotusDocument doc, String text) {
+    // 恢复
+    for (var i = 0; i < _result.length; i++) {
+      RegExpMatch item = _result[i];
+      doc.format(item.start, item.end - item.start, NotusAttribute.highlight.unset, search: true);
+    }
     if (text.isNotEmpty) {
-      var result = RegExp(r''+ text + '', caseSensitive: false, multiLine: true).allMatches(NotusDocument.fromDelta(delta).toPlainText()).toList();
-      for (var item in result) {
-        doc.format(item.start, item.end - item.start, NotusAttribute.highlight, search: true);
+      int offset = 0;
+      _result = RegExp(r''+ text + '', caseSensitive: false, multiLine: true).allMatches(doc.toPlainText()).toList();
+      for (var i = 0; i < _result.length; i++) {
+        RegExpMatch item = _result[i];
+        if (i == 0) {
+          offset = item.end;
+        }
+        doc.format(item.start, item.end - item.start, NotusAttribute.highlight.fromDouble(i == 0 ? 0.8 : 0.5), search: true);
       }
+      _entity = _entity.copyWith(current: _result.isEmpty ? 0 : 1, total: _result.length, offset: offset);
+    } else {
+      _entity = SearchResultEntity();
+    }
+    return _entity;
+  }
+
+  SearchResultEntity next(NotusDocument doc) {
+    if (_entity.hasNext) {
+      RegExpMatch current = _result[_entity.current - 1]; // 0 => 1
+      doc.format(current.start, current.end - current.start, NotusAttribute.highlight.fromDouble(0.5), search: true);
+
+      RegExpMatch item = _result[_entity.current];
+      doc.format(item.start, item.end - item.start, NotusAttribute.highlight.fromDouble(0.8), search: true);
+      int next = _entity.current + 1;
+      _entity = _entity.copyWith(current: next, offset: item.end); // 1 => 2
     }
+    return _entity;
+  }
+  SearchResultEntity prev(NotusDocument doc) {
+    if (_entity.hasPrev) {
+      RegExpMatch current = _result[_entity.current - 1];
+      doc.format(current.start, current.end - current.start, NotusAttribute.highlight.fromDouble(0.5), search: true);
+      
+      RegExpMatch item = _result[_entity.current - 2];
+      doc.format(item.start, item.end - item.start, NotusAttribute.highlight.fromDouble(0.8), search: true);
+      int prev = _entity.current - 1;
+      _entity = _entity.copyWith(current: prev == 0 ? 1 : prev, offset: item.end); // 1 => 2
+    }
+    return _entity;
+  }
+}
+
+class SearchResultEntity {
+  final int total;
+  final int current;
+  final bool hasPrev;
+  final bool hasNext;
+  final int offset;
+
+  const SearchResultEntity({this.total = 0, this.current = 0, this.offset = 0}) : hasPrev = current > 1, hasNext = current < total;
+
+  SearchResultEntity copyWith({
+    int total,
+    int current,
+    int offset,
+  }) {
+    return SearchResultEntity(
+      total: total ?? this.total,
+      current: current ?? this.current,
+      offset: offset ?? this.offset,
+    );
   }
 }

packages/zefyr/example/lib/src/full_page.dart

   bool _editing = false;
   StreamSubscription<NotusChange> _sub;
   bool _darkTheme = false;
+  SearchResultEntity _searchResultEntity = SearchResultEntity();
 
   @override
   void initState() {
         children: <Widget>[
           Container(
             height: 50,
-            child: TextField(
-              onChanged: (text) {
-                _controller.search(text);
-              },
+            child: Row(
+              children: <Widget>[
+                Expanded(
+                                  child: TextField(
+                    onChanged: (text) {
+                      SearchResultEntity a = _controller.search(text);
+                      setState(() {
+                        _searchResultEntity = a;
+                      });
+                    },
+                  ),
+                ),
+                Container(
+                  padding: EdgeInsets.symmetric(horizontal: 10),
+                  child: Text('${_searchResultEntity.current} / ${_searchResultEntity.total}'),
+                )
+              ],
             )
           ),
+          Container(
+            child: Row(
+              children: <Widget>[
+                FlatButton(
+                  onPressed: () {
+                    SearchResultEntity a = _controller.searchPrev();
+                    setState(() {
+                      _searchResultEntity = a;
+                    });
+                  },
+                  child: Text('上一个'),
+                ),
+                FlatButton(
+                  onPressed: () {
+                    SearchResultEntity a = _controller.searchNext();
+                    setState(() {
+                      _searchResultEntity = a;
+                    });
+                  },
+                  child: Text('下一个'),
+                ),
+                FlatButton(
+                  onPressed: () {
+                    SearchResultEntity a = _controller.search('');
+                    setState(() {
+                      _searchResultEntity = a;
+                    });
+                  },
+                  child: Text('完成'),
+                ),
+              ],
+            ),
+          ),
           Expanded(
                       child: ZefyrScaffold(
                     child: ZefyrTheme(
     return GestureDetector(
       behavior: HitTestBehavior.translucent,
       onTap: () {
-        _focusNode.unfocus();
+        FocusScope.of(context).unfocus();
       },
       child: Theme(
         data: ThemeData(primarySwatch: Colors.cyan),

packages/zefyr/lib/src/widgets/common.dart

       result = result.merge(theme.attributeTheme.link);
     }
     if (style.contains(NotusAttribute.highlight)) {
-      result = result.merge(theme.attributeTheme.highlight);
+      result = result.merge(theme.attributeTheme.highlight.copyWith(
+        backgroundColor: theme.attributeTheme.highlight.backgroundColor.withOpacity(style.value<double>(NotusAttribute.highlight)),
+      ));
     }
     if (style.contains(NotusAttribute.color)) {
       final hexStringToColor = (String hex) {

packages/zefyr/lib/src/widgets/controller.dart

     }
   }
 
-  void search(String text) {
-    document.search(text);
-    _lastChangeSource = ChangeSource.remote;
+  SearchResultEntity search(String text) {
+    SearchResultEntity result = document.search(text);
+    updateSelection(TextSelection.collapsed(offset: result.offset), source: ChangeSource.remote);
     notifyListeners();
-    // var result = RegExp(r''+ text + '', caseSensitive: false, multiLine: true).allMatches(plainTextEditingValue.text).toList();
-    // for (var item in result) {
-    //   formatText(item.start, item.end - item.start, NotusAttribute.highlight, ignoreChange: true);
-    // }
+    return result;
+  }
+
+  SearchResultEntity searchPrev() {
+    SearchResultEntity result = document.searchPrev();
+    updateSelection(TextSelection.collapsed(offset: result.offset), source: ChangeSource.remote);
+    notifyListeners();
+    return result;
+  }
+
+  SearchResultEntity searchNext() {
+    SearchResultEntity result = document.searchNext();
+    updateSelection(TextSelection.collapsed(offset: result.offset), source: ChangeSource.remote);
+    notifyListeners();
+    return result;
   }
   
   /// Returns style of specified text range.

packages/zefyr/lib/src/widgets/editable_text.dart

       controls: widget.selectionControls ?? defaultSelectionControls(context),
     ));
 
-    return Stack(fit: StackFit.expand, children: layers);
+    return Stack(fit: StackFit.passthrough, children: layers);
   }
 
   @override

packages/zefyr/lib/src/widgets/input.dart

 
   @override
   void performAction(TextInputAction action) {
-    // no-op
+    final val = _lastKnownRemoteTextEditingValue;
+    onValueChanged(val.selection.start, '', '\n',TextSelection.collapsed(offset: val.selection.start + 1));
   }
 
   @override

packages/zefyr/lib/src/widgets/scaffold.dart

   @override
   Widget build(BuildContext context) {
     final toolbar =
-        (_toolbarBuilder == null) ? Container() : _toolbarBuilder(context);
+        (_toolbarBuilder == null) ? Container(height: MediaQuery.of(context).viewInsets.bottom,) : _toolbarBuilder(context);
     return _ZefyrScaffoldAccess(
         scaffold: this,
         child: Column(