fix search

packages/notus/lib/src/document.dart

     }
   }
 
-  SearchResultEntity search(String text) {
+  SearchResultEntity search([String text = '']) {
     return _searchController.search(this, text);
   }
 

packages/notus/lib/src/search.dart

   List<RegExpMatch> _result = [];
   SearchResultEntity _entity = const SearchResultEntity();
 
-  SearchResultEntity search(NotusDocument doc, String text) {
+  SearchResultEntity search(NotusDocument doc, [String text = '']) {
     // 恢复
     for (var i = 0; i < _result.length; i++) {
       RegExpMatch item = _result[i];

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

     final RenderAbstractViewport viewport = RenderAbstractViewport.of(object);
     assert(viewport != null);
     final lineTheme = ZefyrTheme.of(context).defaultLineTheme;
+    final lineHieght = lineTheme.textStyle.fontSize * lineTheme.textStyle.height;
 
     final double offset = scrollable.position.pixels;
     double target = viewport.getOffsetToReveal(object, 0.0).offset;
     if (target - offset < 0.0) {
-      scrollable.position.jumpTo(target + lineTheme.textStyle.fontSize);
+      scrollable.position.jumpTo(target + lineHieght);
       return;
     }
     target = viewport.getOffsetToReveal(object, 1.0).offset;
     if (target - offset > 0.0) {
-      scrollable.position.jumpTo(target + lineTheme.textStyle.fontSize);
+      scrollable.position.jumpTo(target + lineHieght);
     }
   }
 

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

   SearchResultEntity search(String text) {
     SearchResultEntity result = document.search(text);
     updateSelection(TextSelection.collapsed(offset: result.offset), source: ChangeSource.remote);
-    notifyListeners();
+    return result;
+  }
+
+  SearchResultEntity closeSearch() {
+    SearchResultEntity result = document.search();
+    updateSelection(TextSelection.collapsed(offset: result.offset), source: ChangeSource.remote);
     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;
   }