Set thumbVisibility true for grammar activity scrolling (#3942)

* Set thumbVisibility true for grammar activity scrolling

* always show scrollbar

---------

Co-authored-by: ggurdin <ggurdin@gmail.com>
Co-authored-by: ggurdin <46800240+ggurdin@users.noreply.github.com>

lib/pangea/toolbar/reading_assistance_input_row/reading_assistance_input_bar.dart

@@ -12,7 +12,7 @@ import 'package:fluffychat/pangea/toolbar/widgets/practice_mode_buttons.dart';
 
 const double minContentHeight = 120;
 
-class ReadingAssistanceInputBar extends StatelessWidget {
+class ReadingAssistanceInputBar extends StatefulWidget {
   final ChatController controller;
   final MessageOverlayController overlayController;
 
@@ -22,6 +22,21 @@ class ReadingAssistanceInputBar extends StatelessWidget {
     super.key,
   });
 
+  @override
+  ReadingAssistanceInputBarState createState() =>
+      ReadingAssistanceInputBarState();
+}
+
+class ReadingAssistanceInputBarState extends State<ReadingAssistanceInputBar> {
+  final ScrollController _scrollController = ScrollController();
+  MessageOverlayController get overlayController => widget.overlayController;
+
+  @override
+  void dispose() {
+    _scrollController.dispose();
+    super.dispose();
+  }
+
   Widget barContent(BuildContext context) {
     Widget? content;
     final target =
@@ -120,8 +135,13 @@ class ReadingAssistanceInputBar extends StatelessWidget {
               duration: const Duration(
                 milliseconds: AppConfig.overlayAnimationDuration,
               ),
-              child: SingleChildScrollView(
-                child: barContent(context),
+              child: Scrollbar(
+                thumbVisibility: true,
+                controller: _scrollController,
+                child: SingleChildScrollView(
+                  controller: _scrollController,
+                  child: barContent(context),
+                ),
               ),
             ),
           ),

lib/pangea/toolbar/widgets/practice_activity/multiple_choice_activity.dart

@@ -258,15 +258,12 @@ class MultipleChoiceActivityState extends State<MultipleChoiceActivity> {
 
     return ConstrainedBox(
       constraints: const BoxConstraints(
-        // see https://github.com/pangeachat/client/issues/1422
         maxWidth: AppConfig.toolbarMinWidth,
         maxHeight: AppConfig.toolbarMaxHeight,
       ),
-      child: SingleChildScrollView(
-        child: Padding(
-          padding: const EdgeInsets.all(8),
-          child: content,
-        ),
+      child: Padding(
+        padding: const EdgeInsets.all(8),
+        child: content,
       ),
     );
   }