Fix: PreserveInlineStylesRule (#1980)

lib/src/models/documents/attribute.dart

@@ -116,7 +116,9 @@ class Attribute<T> extends Equatable {
 
   static const VideoAttribute video = VideoAttribute(null);
 
-  static final Set<String> inlineKeys = {
+  static final registeredAttributeKeys = Set.unmodifiable(_registry.keys);
+
+  static final inlineKeys = Set.unmodifiable(<String>{
     Attribute.bold.key,
     Attribute.subscript.key,
     Attribute.superscript.key,
@@ -128,7 +130,17 @@ class Attribute<T> extends Equatable {
     Attribute.color.key,
     Attribute.background.key,
     Attribute.placeholder.key,
-  };
+    Attribute.font.key,
+    Attribute.size.key,
+    Attribute.inlineCode.key,
+  });
+
+  static final ignoreKeys = Set.unmodifiable(<String>{
+    Attribute.width.key,
+    Attribute.height.key,
+    Attribute.style.key,
+    Attribute.token.key,
+  });
 
   static final Set<String> blockKeys = LinkedHashSet.of({
     Attribute.header.key,

lib/src/models/rules/insert.dart

@@ -556,26 +556,47 @@ class PreserveInlineStylesRule extends InsertRule {
       return null;
     }
 
-    final itr = DeltaIterator(document.toDelta());
+    final documentDelta = document.toDelta();
+    final itr = DeltaIterator(documentDelta);
     var prev = itr.skip(len == 0 ? index : index + 1);
 
     if (prev == null || prev.data is! String) return null;
 
-    if ((prev.data as String).endsWith('\n')) {
-      if (prev.attributes != null) {
-        for (final key in prev.attributes!.keys) {
-          if (!Attribute.inlineKeys.contains(key)) {
-            return null;
+    /// Trap for simple insertions at start of line
+    if (len == 0) {
+      final prevData = prev.data as String;
+      if (prevData.endsWith('\n')) {
+        /// If current line is empty get attributes from a prior line
+        final currLine = itr.next();
+        final currData = currLine.data as String?;
+        if (currData != null && (currData.isEmpty || currData[0] == '\n')) {
+          if (prevData.trimRight().isEmpty) {
+            final back =
+                DeltaIterator(documentDelta).skip(index - prevData.length);
+            if (back != null && back.data is String) {
+              prev = back;
+            }
           }
+        } else {
+          prev = currLine;
         }
       }
-      prev = itr
-          .next(); // at the start of a line, apply the style for the current line and not the style for the preceding line
     }
 
-    final attributes = prev.attributes;
+    final attributes = <String, dynamic>{};
+    if (prev.attributes != null) {
+      for (final entry in prev.attributes!.entries) {
+        if (Attribute.inlineKeys.contains(entry.key)) {
+          attributes[entry.key] = entry.value;
+        }
+      }
+    }
+    if (attributes.isEmpty) {
+      return null;
+    }
+
     final text = data;
-    if (attributes == null || !attributes.containsKey(Attribute.link.key)) {
+    if (attributes.isEmpty || !attributes.containsKey(Attribute.link.key)) {
       return Delta()
         ..retain(index + (len ?? 0))
         ..insert(text, attributes);

lib/src/widgets/raw_editor/raw_editor_actions.dart

@@ -460,6 +460,7 @@ class QuillEditorOpenSearchAction extends ContextAction<OpenSearchIntent> {
       );
     }
     await showDialog<String>(
+      barrierColor: Colors.transparent,
       context: context,
       builder: (_) => FlutterQuillLocalizationsWidget(
         child: QuillToolbarSearchDialog(

test/utils/attributes_test.dart

@@ -0,0 +1,47 @@
+import 'package:flutter_quill/flutter_quill.dart';
+import 'package:test/test.dart';
+
+void main() {
+  /// Attributes are assigned an AttributeScope to define how they are used.
+  /// Collections of Attribute keys are used to allow quick iteration by type of scope.
+  group('collections of keys', () {
+    test('unmodifiable inlineKeys', () {
+      expect(() => Attribute.inlineKeys.add('value'),
+          throwsA(const TypeMatcher<UnsupportedError>()));
+    });
+
+    /// All registered attributes should be listed in collections of keys.
+    test('collections of keys', () {
+      final all = <String>{}..addAll(Attribute.registeredAttributeKeys);
+      for (final key in Attribute.inlineKeys) {
+        expect(all.remove(key), true);
+      }
+      for (final key in Attribute.blockKeys) {
+        expect(all.remove(key), true);
+      }
+      for (final key in Attribute.embedKeys) {
+        expect(all.remove(key), true);
+      }
+      for (final key in Attribute.ignoreKeys) {
+        expect(all.remove(key), true);
+      }
+      expect(all, <String>{});
+    });
+
+    /// verify collections contain the correct AttributeScope.
+    test('collections of scope', () {
+      for (final key in Attribute.inlineKeys) {
+        expect(Attribute.fromKeyValue(key, null)!.scope, AttributeScope.inline);
+      }
+      for (final key in Attribute.blockKeys) {
+        expect(Attribute.fromKeyValue(key, null)!.scope, AttributeScope.block);
+      }
+      for (final key in Attribute.embedKeys) {
+        expect(Attribute.fromKeyValue(key, null)!.scope, AttributeScope.embeds);
+      }
+      for (final key in Attribute.ignoreKeys) {
+        expect(Attribute.fromKeyValue(key, null)!.scope, AttributeScope.ignore);
+      }
+    });
+  });
+}