SelectableText with NeverScrollableScrollPhysics needs unique PageStorageKey to not conflict with parent Scrollable

[saibotma]

Is there an existing issue for this?

• I have searched the existing issues
• I have read the guide to filing a bug

Steps to reproduce

1. Run the example (best on iOS)
2. Open "Tab 0"
3. Scroll down until the text is visible
4. Make sure that scrolling has ended, so that it got persisted in page storage
5. Switch to "Tab 1"
6. Switch back to "Tab 0"
7. Notice that the scroll position got restored correctly, but that the text scrolls weirdly
8. Switch back to "Tab 1"
9. Switch back to "Tab 0" and notice that the scroll position did reset to 0

Expected results

• Text should not scroll, because it has NeverScrollableScrollPhysics set.
• Scroll position should not reset to 0, but stay at the previous position.

Actual results

• Text scrolls, obviously restoring its scroll state from the previously stored scroll position of the parent ListView.
• Scroll position resets to 0, because this is what the SelectableText persisted to page storage.

It works, when the SelectableText gets its own unique PageStorageKey, however this is not very obvious because:

• you (me at least) don't expect that SelectableText can actually scroll.
• a scrollable with NeverScrollableScrollPhysics should have scrolling disabled.

Code sample

Code sample

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

final _bucket = PageStorageBucket();

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: PageStorageBug(),
    );
  }
}

class PageStorageBug extends StatefulWidget {
  const PageStorageBug({Key? key}) : super(key: key);

  @override
  State<PageStorageBug> createState() => _PageStorageBugState();
}

class _PageStorageBugState extends State<PageStorageBug> {
  int _tabIndex = 0;

  @override
  Widget build(BuildContext context) {
    return PageStorage(
      bucket: _bucket,
      child: Scaffold(
        body: _tabIndex == 0
            ? const Tab(key: ValueKey(0), title: "Tab 0")
            : const Tab(key: ValueKey(1), title: "Tab 1"),
        bottomNavigationBar: BottomNavigationBar(
          currentIndex: _tabIndex,
          items: const [
            BottomNavigationBarItem(
              icon: Icon(Icons.access_alarm),
              label: "Tab 0",
            ),
            BottomNavigationBarItem(icon: Icon(Icons.add), label: "Tab 1")
          ],
          onTap: (index) => setState(() => _tabIndex = index),
        ),
      ),
    );
  }
}

class Tab extends StatelessWidget {
  final String title;

  const Tab({required this.title, Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Scrollbar(
        child: ListView(
          key: PageStorageKey("$title-main"),
          children: [
            Container(height: 1000, color: Colors.blue),
            SelectableText(
              // It obviously works, when this key is set.
              //key: PageStorageKey("$title-text"),
              title,
              style: const TextStyle(fontSize: 50),
              scrollPhysics: const NeverScrollableScrollPhysics(),
            ),
            Container(height: 3000, color: Colors.red),
          ],
        ),
      ),
    );
  }
}

Screenshots or Video

Screenshots / Video demonstration

Screen.Recording.2023-06-19.at.14.56.24.mov

Logs

Logs

[Paste your logs here]

Flutter Doctor output

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! Doctor found issues in 1 category.

[darshankawar]

Thanks for the detailed report. This is replicable on Android too, so doesn't look specific to iOS.

stable, master flutter doctor -v

[!] Flutter (Channel stable, 3.10.5, on macOS 12.2.1 21D62 darwin-x64, locale
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[Piinks]

Hi @saibotma, this looks like based on the code in the OP this is working as expected.

a scrollable with NeverScrollableScrollPhysics should have scrolling disabled.

In the code sample, NeverScrollableScrollPhysics is set on the SelectableText, not the ListView. So the physics you have applied only applies to SelectableText.

To set scroll physics in a way that descendent scrollables will all uniformly adopt, use ScrollBehavior. I did notice looking at this that SelectableText does not inherit from ScrollBehavior, so I filed #129206 to follow up on that.

It looks like there is more than one issue stated in the OP, can you share details of the other issue, just to be sure we are mixing them up?

[saibotma]

Hi @Piinks, thanks for the answer. I think that you've not understood my issue correctly, yet.

The NeverScrollableScrollPhysics obviously should only apply to the SelectableText and they also do (you cannot scroll it with your finger). However when you take another close look at the video you will see that the SelectableText scrolls without user interaction, because (I assume) it tries to restore scroll state from PageStorage.

[Piinks]

Thank for providing more context! I am not sure what is happening here then... maybe @chunhtai or @Hangyujin have an idea? I think they are more familiar with SelectableText.

[gildaswise]

I'm having a similar issue in Flutter Web and I can confirm that adding a PageStorage above each SelectableText solves the issue. Without it, this happens even with NeverScrollableScrollPhysics:

Video demonstration

Screen.Recording.2023-09-18.at.11.45.22.mov