Inline toggle style feature (#169)

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

   /// Source of the last text or selection change.
   ChangeSource get lastChangeSource => _lastChangeSource;
 
+  /// Store any styles attribute that got toggled by the tap of a button
+  /// and that has not been applied yet.
+  /// It gets reseted after each format action within the [document].
+  NotusStyle get toggledStyles => _toggledStyles;
+  NotusStyle _toggledStyles = new NotusStyle();
+
   /// Updates selection with specified [value].
   ///
   /// [value] and [source] cannot be `null`.
   /// Resulting change is registered as produced by user action, e.g.
   /// using [ChangeSource.local].
   ///
+  /// It also applies the toggledStyle if needed. And then it resets it
+  /// in any cases as we don't want to keep it except on inserts.
+  ///
   /// Optionally updates selection if provided.
   void replaceText(int index, int length, String text,
       {TextSelection selection}) {
 
     if (length > 0 || text.isNotEmpty) {
       delta = document.replace(index, length, text);
+      // If the delta is a classical insert operation and we have toggled
+      // some style, then we apply it to our document.
+      if (delta != null &&
+          toggledStyles.isNotEmpty &&
+          delta.length == 2 &&
+          delta[1].isInsert) {
+        // Apply it.
+        Delta retainDelta = new Delta()
+          ..retain(index)
+          ..retain(1, toggledStyles.toJson());
+        document.compose(retainDelta, ChangeSource.local);
+      }
     }
 
+    // Always reset it after any user action, even if it has not been applied.
+    _toggledStyles = new NotusStyle();
+
     if (selection != null) {
       if (delta == null) {
         _updateSelectionSilent(selection, source: ChangeSource.local);
   void formatText(int index, int length, NotusAttribute attribute) {
     final change = document.format(index, length, attribute);
     _lastChangeSource = ChangeSource.local;
+
+    if (length == 0 &&
+        (attribute.key == NotusAttribute.bold.key ||
+            attribute.key == NotusAttribute.italic.key)) {
+      // Add the attribute to our toggledStyle. It will be used later upon insertion.
+      _toggledStyles = toggledStyles.put(attribute);
+    }
+
     // Transform selection against the composed change and give priority to
     // the change. This is needed in cases when format operation actually
     // inserts data into the document (e.g. embeds).
     formatText(index, length, attribute);
   }
 
+  /// Returns style of specified text range.
+  ///
+  /// If nothing is selected but we've toggled an attribute,
+  ///  we also merge those in our style before returning.
   NotusStyle getSelectionStyle() {
     int start = _selection.start;
     int length = _selection.end - start;
-    return _document.collectStyle(start, length);
+    var lineStyle = _document.collectStyle(start, length);
+
+    lineStyle = lineStyle.mergeAll(toggledStyles);
+
+    return lineStyle;
   }
 
   TextEditingValue get plainTextEditingValue {

packages/zefyr/test/widgets/controller_test.dart

       expect(controller.lastChangeSource, ChangeSource.local);
     });
 
+    test('formatText with toggled style enabled', () {
+      bool notified = false;
+      controller.addListener(() {
+        notified = true;
+      });
+      controller.replaceText(0, 0, 'Words');
+      controller.formatText(2, 0, NotusAttribute.bold);
+      // Test that doing nothing does reset the toggledStyle.
+      controller.replaceText(2, 0, '');
+      controller.replaceText(2, 0, 'n');
+      controller.formatText(3, 0, NotusAttribute.bold);
+      controller.replaceText(3, 0, 'B');
+      expect(notified, isTrue);
+
+      expect(
+        controller.document.toDelta(),
+        new Delta()
+          ..insert('Won')
+          ..insert('B', NotusAttribute.bold.toJson())
+          ..insert('rds')
+          ..insert('\n'),
+      );
+      expect(controller.lastChangeSource, ChangeSource.local);
+    });
+
+    test('insert text with toggled style unset', () {
+      bool notified = false;
+      controller.addListener(() {
+        notified = true;
+      });
+      controller.replaceText(0, 0, 'Words');
+      controller.formatText(1, 0, NotusAttribute.bold);
+      controller.replaceText(1, 0, 'B');
+      controller.formatText(2, 0, NotusAttribute.bold.unset);
+      controller.replaceText(2, 0, 'u');
+
+      expect(notified, isTrue);
+      expect(
+        controller.document.toDelta(),
+        new Delta()
+          ..insert('W')
+          ..insert('B', NotusAttribute.bold.toJson())
+          ..insert('uords')
+          ..insert('\n'),
+      );
+      expect(controller.lastChangeSource, ChangeSource.local);
+    });
+
     test('formatSelection', () {
       bool notified = false;
       controller.addListener(() {
       var result = controller.getSelectionStyle();
       expect(result.values, [NotusAttribute.bold]);
     });
+
+    test('getSelectionStyle with toggled style', () {
+      var selection = new TextSelection.collapsed(offset: 3);
+      controller.replaceText(0, 0, 'Words', selection: selection);
+      controller.formatText(3, 0, NotusAttribute.bold);
+
+      var result = controller.getSelectionStyle();
+      expect(result.values, [NotusAttribute.bold]);
+    });
   });
 }