fix: 🐛 Showcase stuck when animation is disabled on web

- Fix detailscreen to use cached version of the scope to avoid race conditions.

Author: aditya-chavda

example/lib/detailscreen.dart

@@ -11,16 +11,16 @@ class Detail extends StatefulWidget {
 class _DetailState extends State<Detail> {
   final GlobalKey _one = GlobalKey();
   BuildContext? myContext;
-  final scopeName = "_detailsScreen";
+
+  // This is optional but if you need different configuration in
+  // ShowcaseView then you can register new ShowcaseView
+  final showcaseDetailScope = ShowcaseView.register(scope: "_detailsScreen");
 
   @override
   void initState() {
     super.initState();
-    // This is optional but if you need different configuration in
-    // ShowcaseView then you can register new ShowcaseView
-    ShowcaseView.register(scope: scopeName);
     WidgetsBinding.instance.addPostFrameCallback(
-      (_) => ShowcaseView.getNamed(scopeName)
+      (_) => showcaseDetailScope
         ..startShowCase([_one], delay: const Duration(milliseconds: 200))
         ..addOnFinishCallback(_onShowcaseFinished)
         ..addOnDismissCallback(_onShowcaseDismissed),
@@ -29,7 +29,7 @@ class _DetailState extends State<Detail> {
 
   @override
   void dispose() {
-    ShowcaseView.getNamed(scopeName)
+    showcaseDetailScope
       ..removeOnFinishCallback(_onShowcaseFinished)
       ..removeOnDismissCallback(_onShowcaseDismissed);
     super.dispose();
@@ -76,7 +76,7 @@ class _DetailState extends State<Detail> {
                     style: ElevatedButton.styleFrom(
                       backgroundColor: const Color(0xffEE5366),
                     ),
-                    onPressed: ShowcaseView.getNamed(scopeName).dismiss,
+                    onPressed: showcaseDetailScope.dismiss,
                     child: const Text(
                       'Close Showcase',
                       style: TextStyle(

lib/src/showcase/showcase_controller.dart

@@ -19,9 +19,11 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+import 'dart:async';
 import 'dart:math';
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 
 import '../models/flutter_inherited_data.dart';
@@ -210,7 +212,7 @@ class ShowcaseController {
     bool shouldUpdateOverlay = true,
   }) {
     if (!showcaseView.enableShowcase || !showcaseView.isShowcaseRunning) return;
-    WidgetsBinding.instance.addPostFrameCallback((_) {
+    _runLater(() {
       if (!context.mounted ||
           !showcaseView.enableShowcase ||
           !showcaseView.isShowcaseRunning) {
@@ -443,6 +445,18 @@ class ShowcaseController {
   FloatingActionWidget? get _getFloatingActionWidget =>
       config.floatingActionWidget ?? globalFloatingActionWidget;
 
+  /// Schedules a callback to run after the current frame with guarantee.
+  void _runLater(VoidCallback process) {
+    final scheduler = SchedulerBinding.instance;
+    // Schedule a frame if none is scheduled to ensure the callback runs.
+    // This is useful particularly when [disableMovingAnimation] is true and so
+    // flutter doesn't another frame on web.
+    if (!scheduler.hasScheduledFrame) {
+      scheduler.scheduleFrame();
+    }
+    scheduler.addPostFrameCallback((_) => process());
+  }
+
   @override
   int get hashCode => Object.hash(id, key);