Fix Hero animation when drag-dismissing WoltModalSheet at zero threshold

[ArinFaraj]

Description

Fixes an issue where Hero widgets fail to animate properly when drag-dismissing a WoltModalSheet that reaches a near-zero position. Previously, when dragging the sheet to a position very close to zero and releasing, the Hero widgets on the underlying route would not animate back correctly, while they worked fine when drag-dismissing from halfway or using fling gestures.

The fix prevents the animation controller from reaching a fully dismissed state during drag operations by implementing a minimum threshold of 0.01. This ensures the proper dismissal sequence is always followed, allowing Hero widgets to complete their transitions correctly.

Changes:

• Added minimum threshold check in vertical and horizontal drag update handlers
• Ensures consistent Hero widget behavior across all dismissal scenarios

Sample Code

import 'package:flutter/material.dart';
import 'package:wolt_modal_sheet/wolt_modal_sheet.dart';

void main() {
  runApp(
    MaterialApp(
      title: 'Flutter Demo',
      home: Builder(
        builder: (context) {
          return Scaffold(
            body: Padding(
              padding: const EdgeInsets.all(40),
              child: Align(
                alignment: Alignment.bottomCenter,
                child: ElevatedButton(
                  onPressed: () {
                    showWoltDialog(context);
                  },
                  child: Hero(
                    tag: 'hero',
                    child: const Icon(Icons.person, size: 100),
                  ),
                ),
              ),
            ),
          );
        },
      ),
    ),
  );
}

void showWoltDialog(BuildContext context) {
  WoltModalSheet.show(
    context: context,
    modalTypeBuilder: (context) => WoltModalType.bottomSheet(),
    pageListBuilder:
        (bottomSheetContext) => [
          WoltModalSheetPage(
            child: Hero(
              tag: 'hero',
              child: const Icon(Icons.person, size: 100),
            ),
          ),
        ],
  );
}

Sample video

Recording.2025-03-04.212803.mp4

Related Issues

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• My PR includes tests for all changed/updated/fixed behaviors.
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
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Breaking Change

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• Yes, this is a breaking change.
• No, this is not a breaking change.

[ulusoyca]

@TahaTesser Do you think you may have time to check this?

[TahaTesser]

Thank you for contributing!

Introducing a threshold might make sense with more information.

Previously, when dragging the sheet to a position very close to zero and releasing, the Hero widgets on the underlying route would not animate back correctly, while they worked fine when drag-dismissing from halfway or using fling gestures.

Could you please share a code sample to reproduce this behavior? It would be great in the context of this fix. I can reproduce the described behavior with a sample and write tests to verify that this fix is consistent.

[ArinFaraj]

Thank you for your time, I have updated the pr with a code sample and a video of the issue

[TahaTesser]

Thank you for your time, I have updated the pr with a code sample and a video of the issue

Thanks so much for the code sample and demo video. I've tried both iOS, Android, and macOS desktop. I couldn't reproduce the failed Hero animation as seen in your demo. Could you please share where you reproduced it and how you ensured this is consistent?

[ArinFaraj]

Since i can reproduce it in a new flutter project with the latest flutter version and package version, here are the steps to reproduce:

• Create a flutter project and add wolt_modal_sheet package
• Copy and paste the sample code into the main file
• Run on any platform
• Open the sheet
• Start dragging the sheet down until it reaches zero (completely hidden)
• Stop the drag and you will see that the sheet is gone but the hero widget has not come back to its original place (the hero did not have time to animate because the transition duration became 0, since the transition starts once you stop dragging)

[TahaTesser]

• Start dragging the sheet down until it reaches zero (completely hidden)
• Stop the drag and you will see that the sheet is gone but the hero widget has not come back to its original place (the hero did not have time to animate because the transition duration became 0, since the transition starts once you stop dragging)

Following these steps, Hero widget always appear in my sample reproduction. I couldn't get the blank button like show in your demo.

External.Device.mp4