Send empty composing range to engine if invalid

packages/fleather/lib/src/widgets/editor_input_client_mixin.dart

@@ -2,6 +2,8 @@ import 'dart:math';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/painting.dart';
+import 'package:flutter/rendering.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
@@ -95,7 +97,7 @@ mixin RawEditorStateTextInputClientMixin on EditorState
     // with the last known remote value.
     // It is important to prevent excessive remote updates as it can cause
     // race conditions.
-    final actualValue = value.copyWith(
+    var actualValue = value.copyWith(
       composing: _lastKnownRemoteTextEditingValue?.composing,
     );
 
@@ -107,6 +109,16 @@ mixin RawEditorStateTextInputClientMixin on EditorState
       performSpellCheck(value.text);
     }
 
+    // This is to prevent sending an editing state with invalid composing range
+    // to engine.
+    // TODO: Maybe it's better to also include composing range in controller?
+    // Actions like [_DeleteTextAction] are using controller's editing value
+    // to update remote value.
+    // See https://github.com/fleather-editor/fleather/issues/259#issuecomment-2032404450
+    if (!actualValue.isComposingRangeValid) {
+      actualValue = actualValue.copyWith(composing: TextRange.empty);
+    }
+
     _lastKnownRemoteTextEditingValue = actualValue;
     _textInputConnection!.setEditingState(actualValue);
   }