Smart text nodes rerendering.

src/view/renderer.js

@@ -18,6 +18,7 @@ import remove from '@ckeditor/ckeditor5-utils/src/dom/remove';
 import ObservableMixin from '@ckeditor/ckeditor5-utils/src/observablemixin';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
 import isText from '@ckeditor/ckeditor5-utils/src/dom/istext';
+import diffToChanges from '@ckeditor/ckeditor5-utils/src/difftochanges';
 
 /**
  * Renderer updates DOM structure and selection, to make them a reflection of the view structure and selection.
@@ -426,7 +427,15 @@ export default class Renderer {
 		}
 
 		if ( actualText != expectedText ) {
-			domText.data = expectedText;
+			const actions = diffToChanges( diff( actualText, expectedText ), expectedText );
+
+			for ( const action of actions ) {
+				if ( action.type === 'insert' ) {
+					domText.insertData( action.index, action.values.join( '' ) );
+				} else { // 'delete'
+					domText.deleteData( action.index, action.howMany );
+				}
+			}
 		}
 	}