fix bug #1696

lib/src/models/documents/document.dart

@@ -114,14 +114,32 @@ class Document {
   /// Returns an instance of [Delta] actually composed into this document.
   Delta replace(int index, int len, Object? data) {
     assert(index >= 0);
-    assert(data is String || data is Embeddable);
+    assert(data is String || data is Embeddable || data is Delta);
+
+    var delta = Delta();
+
+    if (data is Delta) {
+      // move to insertion point and add the inserted content
+      if (index > 0) {
+        delta.retain(index);
+      }
+
+      // remove any text we are replacing
+      if (len > 0) {
+        delta.delete(len);
+      }
 
+      // add the pasted content
+      for (final op in data.operations) {
+        delta.push(op);
+      }
+
+      compose(delta, ChangeSource.local);
+    } else {
       final dataIsNotEmpty = (data is String) ? data.isNotEmpty : true;
 
       assert(dataIsNotEmpty || len > 0);
 
-    var delta = Delta();
-
       // We have to insert before applying delete rules
       // Otherwise delete would be operating on stale document snapshot.
       if (dataIsNotEmpty) {
@@ -132,6 +150,7 @@ class Document {
         final deleteDelta = delete(index, len);
         delta = delta.compose(deleteDelta);
       }
+    }
 
     return delta;
   }

lib/src/widgets/quill/quill_controller.dart

@@ -291,7 +291,7 @@ class QuillController extends ChangeNotifier {
     bool ignoreFocus = false,
     bool shouldNotifyListeners = true,
   }) {
-    assert(data is String || data is Embeddable);
+    assert(data is String || data is Embeddable || data is Delta);
 
     if (onReplaceText != null && !onReplaceText!(index, len, data)) {
       return;

lib/src/widgets/raw_editor/raw_editor_state.dart

@@ -221,22 +221,12 @@ class QuillRawEditorState extends EditorState
         final htmlBody = html_parser.parse(html).body?.outerHtml;
         final deltaFromClipboard = Document.fromHtml(htmlBody ?? html);
 
-        var newDelta = Delta();
-        newDelta = newDelta.compose(deltaFromClipboard);
-        if (!controller.document.isEmpty()) {
-          newDelta = newDelta.compose(controller.document.toDelta());
-        }
-
-        controller
-          ..setContents(
-            newDelta,
-          )
-          ..updateSelection(
+        controller.replaceText(
+            textEditingValue.selection.start,
+            textEditingValue.selection.end - textEditingValue.selection.start,
+            deltaFromClipboard,
             TextSelection.collapsed(
-              offset: controller.document.length,
-            ),
-            ChangeSource.local,
-          );
+                offset: textEditingValue.selection.end));
 
         bringIntoView(textEditingValue.selection.extent);