Remove Primary Scroll Controller for Flutter Desktop apps #100264

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1. domesticmouse

   assigned

   cbracken

   and

   Piinks

   on Mar 17, 2022
2. darshankawar

   added

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   c: proposalA detailed proposal for a change to FlutterA detailed proposal for a change to Flutter

   frameworkflutter/packages/flutter repository. See also f: labels.flutter/packages/flutter repository. See also f: labels.

   f: scrollingViewports, list views, slivers, etc.Viewports, list views, slivers, etc.

   a: desktopRunning on desktopRunning on desktop

   p: material_uimaterial_ui package in flutter/packagesmaterial_ui package in flutter/packages

   and removed

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   on Mar 17, 2022
3. Piinks commented on Mar 17, 2022

   

   Piinks

   on Mar 17, 2022

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   So I think the primary scroll controller is only used in the framework to automatically support the iOS scroll to top function. If this is true, we can likely disable the PSC automatically attaching to every vertical scroll position on desktop...

   I need to investigate if the PSC is relied upon for anything else that would make such a change a breaking one.

   👍React with 👍1Reacted by Brett Morgan
4. Piinks

   unassigned

   cbracken

   on Mar 17, 2022
5. Piinks

   added

   P2Important issues not at the top of the work listImportant issues not at the top of the work list

   on Mar 17, 2022
6. Piinks commented on Mar 29, 2022

   

   Piinks

   on Mar 29, 2022

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   Unfortunately I do not think this will be ass straightforward as I had hoped. Couple of findings:

   1. The PrimaryScrollController is also used in the NestedScrollView in order to have the inner scroll view inherit the scroll controller that it manipulates to keep the 2 positions in sync.

   • So we would have to find a way around this or it would break the NestedScrollView for desktop applications.

   2. Default keyboard scroll actions on desktop actually rely on the PrimaryScrollController to work. A PSC is created for each route, and when the user taps the arrow keys, if the current focus is not enclosed by a scrollable, it looks up the PSC as a fallback to automatically have keyboard scrolling shortcuts work.

   • In this case, I think the same more than one position attached... issue actually applies to scroll actions too, if not I do not think the user would want multiple scroll views to move in response to a key stroke. If we disable the automatic attachment of PSC completely, the user would have to specify which scrollview they want to be the default for scroll actions by setting ScrollView.primary to true. I think this would be an ok trade-off but it is still one to consider carefully.

   ⭐ ➡️ I think for now, the best workaround is to set primary: false on ScrollViews that should not connect to the PSC. I think it is better than setting an individual scroll controller for each.

   If anyone has thoughts on this, please do share. I am still investigating a few more options here.
7. Piinks

   closed this as completedin #102099on Jun 9, 2022
8. github-actions commented on Jun 23, 2022

   

   github-actionsbot

   on Jun 23, 2022

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   This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
9. github-actions

   locked as resolved and limited conversation to collaborators on Jun 23, 2022