fix: unpredictable endless loop of '_handleFocusChanged' in the phase of page route changing when editor is set to readonly. (singerdmx#2488)

Co-authored-by: chaos <[email protected]>

Author: chaosue

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Remove unnecessary content change listeners in read-only mode to avoid triggering infinite loops of **FocusNode** callbacks [#2488](https://github.com/singerdmx/flutter-quill/pull/2488).
 - Remove unicode from `QuillText` element that causes weird caret behavior on empty lines [#2453](https://github.com/singerdmx/flutter-quill/pull/2453).
 - Focus and open context menu on right click if unfocused [#2477](https://github.com/singerdmx/flutter-quill/pull/2477).
 - Update QuillController `length` extension method deprecation message [#2483](https://github.com/singerdmx/flutter-quill/pull/2483).

lib/src/editor/raw_editor/raw_editor_state.dart

@@ -814,8 +814,6 @@ class QuillRawEditorState extends EditorState
       _clipboardStatus!.addListener(_onChangedClipboardStatus);
     }
 
-    controller.addListener(_didChangeTextEditingValueListener);
-
     _scrollController = widget.config.scrollController;
     _scrollController.addListener(_updateSelectionOverlayForScroll);
 
@@ -829,9 +827,6 @@ class QuillRawEditorState extends EditorState
     _floatingCursorResetController = AnimationController(vsync: this);
     _floatingCursorResetController.addListener(onFloatingCursorResetTick);
 
-    // listen to composing range changes
-    composingRange.addListener(_onComposingRangeChanged);
-
     if (isKeyboardOS) {
       _keyboardVisible = true;
     } else if (!kIsWeb && isFlutterTest) {
@@ -858,8 +853,13 @@ class QuillRawEditorState extends EditorState
       });
     }
 
-    // Focus
-    widget.config.focusNode.addListener(_handleFocusChanged);
+    if (!widget.config.readOnly) {
+      controller.addListener(_didChangeTextEditingValueListener);
+      // listen to composing range changes
+      composingRange.addListener(_onComposingRangeChanged);
+      // Focus
+      widget.config.focusNode.addListener(_handleFocusChanged);
+    }
   }
 
   // KeyboardVisibilityController only checks for keyboards that
@@ -965,10 +965,12 @@ class QuillRawEditorState extends EditorState
     assert(!hasConnection);
     _selectionOverlay?.dispose();
     _selectionOverlay = null;
-    controller.removeListener(_didChangeTextEditingValueListener);
-    widget.config.focusNode.removeListener(_handleFocusChanged);
+    if (!widget.config.readOnly) {
+      controller.removeListener(_didChangeTextEditingValueListener);
+      widget.config.focusNode.removeListener(_handleFocusChanged);
+      composingRange.removeListener(_onComposingRangeChanged);
+    }
     _cursorCont.dispose();
-    composingRange.removeListener(_onComposingRangeChanged);
     if (_clipboardStatus != null) {
       _clipboardStatus!
         ..removeListener(_onChangedClipboardStatus)