Fix EditableText _justResumed is not accurate (flutter#177658)

## Description

This PR tweaks the selection logic added in
flutter#157399.
Before this PR (and since
flutter#157399) when the app resumed
while a TextField was selected the selection of the TextField is
maintained. This is the right behavior for the currently focused
TextField. But when there are several TextFields, after the app resumed
and the user move the focus to a another TextField, the behavior should
be to select all the content of the newly focused TextField. To achieve
this the `_justResumed`flag added in
flutter#157399 should be reset as soon
as the focus move as it is needed only for the current focused TextField
to restore its selection just after the app resumed.

## Related Issue

Fixes [Pressing tab does select all content when app is resumed for
TextFields which were not
focused](flutter#177650)

## Tests

- Adds 1 test

Author: bleroux

packages/flutter/lib/src/widgets/editable_text.dart

@@ -3214,10 +3214,23 @@ class EditableTextState extends State<EditableText>
     widget.focusNode.addListener(_handleFocusChanged);
     _cursorVisibilityNotifier.value = widget.showCursor;
     _spellCheckConfiguration = _inferSpellCheckConfiguration(widget.spellCheckConfiguration);
-    _appLifecycleListener = AppLifecycleListener(onResume: () => _justResumed = true);
+    _appLifecycleListener = AppLifecycleListener(onResume: _onResume);
     _initProcessTextActions();
   }
 
+  void _onResume() {
+    _justResumed = true;
+    // To prevent adding multiple listeners, remove any existing one first.
+    FocusManager.instance.removeListener(_resetJustResumed);
+    // Reset _justResumed as soon as there is a focus change.
+    FocusManager.instance.addListener(_resetJustResumed);
+  }
+
+  void _resetJustResumed() {
+    _justResumed = false;
+    FocusManager.instance.removeListener(_resetJustResumed);
+  }
+
   /// Query the engine to initialize the list of text processing actions to show
   /// in the text selection toolbar.
   Future<void> _initProcessTextActions() async {
@@ -3436,6 +3449,7 @@ class EditableTextState extends State<EditableText>
     _cursorVisibilityNotifier.dispose();
     _appLifecycleListener.dispose();
     FocusManager.instance.removeListener(_unflagInternalFocus);
+    FocusManager.instance.removeListener(_resetJustResumed);
     _disposeScrollNotificationObserver();
     super.dispose();
     assert(_batchEditDepth <= 0, 'unfinished batch edits: $_batchEditDepth');

packages/flutter/test/widgets/editable_text_test.dart

@@ -16306,6 +16306,15 @@ void main() {
   });
 
   group('selection behavior when receiving focus', () {
+    Future<void> setAppLifecycleState(AppLifecycleState state) async {
+      final ByteData? message = const StringCodec().encodeMessage(state.toString());
+      await TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        'flutter/lifecycle',
+        message,
+        (_) {},
+      );
+    }
+
     testWidgets('tabbing between fields', (WidgetTester tester) async {
       final bool isDesktop =
           debugDefaultTargetPlatformOverride == TargetPlatform.macOS ||
@@ -16590,12 +16599,6 @@ void main() {
 
     // Regression test for https://github.com/flutter/flutter/issues/156078.
     testWidgets('when having focus regained after the app resumed', (WidgetTester tester) async {
-      Future<void> setAppLifeCycleState(AppLifecycleState state) async {
-        final ByteData? message = const StringCodec().encodeMessage(state.toString());
-        await TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
-            .handlePlatformMessage('flutter/lifecycle', message, (_) {});
-      }
-
       final TextEditingController controller = TextEditingController(text: 'Flutter!');
       addTearDown(controller.dispose);
       final FocusNode focusNode = FocusNode();
@@ -16620,12 +16623,82 @@ void main() {
       expect(focusNode.hasFocus, true);
       expect(controller.selection, collapsedAtEnd('Flutter!').selection);
 
-      await setAppLifeCycleState(AppLifecycleState.inactive);
-      await setAppLifeCycleState(AppLifecycleState.resumed);
+      await setAppLifecycleState(AppLifecycleState.inactive);
+      await setAppLifecycleState(AppLifecycleState.resumed);
 
       expect(focusNode.hasFocus, true);
       expect(controller.selection, collapsedAtEnd('Flutter!').selection);
     }, variant: TargetPlatformVariant.all());
+
+    testWidgets(
+      'moving focus after the app resumed should select all the content on desktop',
+      (WidgetTester tester) async {
+        final TextEditingController controller1 = TextEditingController.fromValue(
+          collapsedAtEnd('Flutter!'),
+        );
+        addTearDown(controller1.dispose);
+        final TextEditingController controller2 = TextEditingController.fromValue(
+          collapsedAtEnd('Dart!'),
+        );
+        addTearDown(controller2.dispose);
+        final FocusNode focusNode1 = FocusNode();
+        addTearDown(focusNode1.dispose);
+        final FocusNode focusNode2 = FocusNode();
+        addTearDown(focusNode2.dispose);
+
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Center(
+              child: Column(
+                children: <Widget>[
+                  EditableText(
+                    key: ValueKey<String>(controller1.text),
+                    controller: controller1,
+                    focusNode: focusNode1,
+                    autofocus: true,
+                    style: Typography.material2018().black.titleMedium!,
+                    cursorColor: Colors.blue,
+                    backgroundCursorColor: Colors.grey,
+                  ),
+                  EditableText(
+                    key: ValueKey<String>(controller2.text),
+                    controller: controller2,
+                    focusNode: focusNode2,
+                    style: Typography.material2018().black.titleMedium!,
+                    cursorColor: Colors.blue,
+                    backgroundCursorColor: Colors.grey,
+                  ),
+                ],
+              ),
+            ),
+          ),
+        );
+
+        expect(focusNode1.hasFocus, true);
+        expect(focusNode2.hasFocus, false);
+        expect(controller1.selection, collapsedAtEnd('Flutter!').selection);
+        expect(controller2.selection, collapsedAtEnd('Dart!').selection);
+
+        // Pause and resume the application.
+        await setAppLifecycleState(AppLifecycleState.inactive);
+        await setAppLifecycleState(AppLifecycleState.resumed);
+
+        // Change focus to the second EditableText.
+        await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+        await tester.pumpAndSettle();
+
+        expect(focusNode1.hasFocus, false);
+        expect(focusNode2.hasFocus, true);
+        expect(controller1.selection, collapsedAtEnd('Flutter!').selection);
+
+        // The text of the second EditableText should be entirely selected.
+        expect(
+          controller2.selection,
+          TextSelection(baseOffset: 0, extentOffset: controller2.text.length),
+        );
+      },
+      variant: TargetPlatformVariant.desktop(),
+    );
   });
 
   testWidgets('EditableText respects MediaQuery.boldText', (WidgetTester tester) async {