[cupertino_ui] Fix CupertinoSheetRoute throwing when a drag ends during a pending relayout by theprantadutta · Pull Request #13316 · flutter/packages

theprantadutta · 2026-10-19T05:42:59Z

Dragging a CupertinoSheetRoute converts drag deltas and the release velocity into fractions of the sheet's height. Both drag paths read that height from context.size: _CupertinoDragGestureDetectorState.sheetHeight for regular sheets, and _dragUpdate / _handleDragEnd in _CupertinoDraggableScrollableSheetState for sheets built with scrollableBuilder. Element.size asserts when the render object is dirty for layout, so a drag that ends while a relayout is pending throws Cannot get size from a render object that has been marked dirty for layout. The reporter saw it cascade into _drag == null asserts in ScrollableState, after which the sheet stopped responding. In release the assert is stripped and the read returns the last laid out size.

The fix reads the height from the RenderBox directly. That's the size the sheet was last laid out at, which is the size the drag was made against, and it's what release builds were already using. The Material BottomSheet reads its height for drag updates and fling velocity the same way (_childHeight).

Tests

Two regression tests, one per drag path. Each starts a partial drag, marks the box the sheet measures as dirty, and releases before the next frame. Both fail on main with the assertion above, and both pass with the fix, with the sheet settling back to where it started. The rest of sheet_test.dart passes as well (44 tests in total).

One limitation: the reporter hit this on a device when the keyboard was dismissed mid-drag. Changing the view insets mid-drag in a widget test doesn't reproduce it, because the relayout that follows lands before the pointer up. So the tests set up the condition from the reporter's stack trace directly, not the keyboard sequence.

Fixes flutter/flutter#194681

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…ng a pending relayout The sheet's drag handlers read context.size to convert drag deltas and velocities into fractions of the sheet height. Element.size asserts when the render object is dirty for layout, so a drag that ended while a relayout was pending threw 'Cannot get size from a render object that has been marked dirty for layout'. Read the size from the render box instead, which is the last laid out height and what release builds already used.

gemini-code-assist

Code Review

This pull request updates the sheet height retrieval in CupertinoSheetRoute to use the render box instead of context.size, preventing assertions when a drag ends during a pending relayout. Corresponding regression tests and a changelog entry are included. The review feedback suggests caching the _sheetHeight value in a local variable within _dragUpdate to avoid redundant render object lookups during drag events.

gemini-code-assist · 2026-10-19T05:44:35Z

  void _dragUpdate(double delta) {
    assert(mounted);
    if (_dragGestureController != null) {
      _dragGestureController!.dragUpdate(
-        delta / (context.size!.height - (context.size!.height * _kTopGapRatio)),
+        delta / (_sheetHeight - (_sheetHeight * _kTopGapRatio)),
        null,
      );
    }


During a drag update, _sheetHeight is accessed twice. Since _sheetHeight performs a tree lookup via context.findRenderObject(), caching this value in a local variable avoids redundant lookups during high-frequency drag events.

Suggested change

void _dragUpdate(double delta) {

assert(mounted);

if (_dragGestureController != null) {

_dragGestureController!.dragUpdate(

delta / (context.size!.height - (context.size!.height * _kTopGapRatio)),

delta / (_sheetHeight - (_sheetHeight * _kTopGapRatio)),

null,

);

}

void _dragUpdate(double delta) {

assert(mounted);

if (_dragGestureController != null) {

final double sheetHeight = _sheetHeight;

_dragGestureController!.dragUpdate(

delta / (sheetHeight - (sheetHeight * _kTopGapRatio)),

null,

);

}

}

…drag-size-during-layout

dkwingsmt

LGTM except for a nit. Thank you for the fix!

dkwingsmt · 2026-11-10T07:42:17Z

+  // Reads the height from the render box instead of context.size, which asserts
+  // when the box is dirty for layout. A drag can end while a relayout is
+  // pending, and the last laid out height is the one the drag was made against.


nit: The verb "assert" is typically followed by the correct behavior, making the sentence a bit awkward to read at first glance.

Suggested change

// Reads the height from the render box instead of context.size, which asserts

// when the box is dirty for layout. A drag can end while a relayout is

// pending, and the last laid out height is the one the drag was made against.

// Reads the height from the render box instead of context.size, which throws

// in debug mode when the box is dirty for layout. A drag can end while a relayout is

// pending, and the last laid out height is the one the drag was made against.

Done in babcf0b, thanks!

dkwingsmt · 2026-11-10T07:45:18Z

  }

+  // See _CupertinoDragGestureDetectorState.sheetHeight.
+  double get _sheetHeight => (context.findRenderObject()! as RenderBox).size.height;


nit: It may help to extract the two methods into a global function. Non-blocking comment. Feel free to decide whether to do it.

Done in babcf0b: both drag paths now call a top-level _sheetHeightOf(context), and each handler reads it once.

Moves the render box height read into a top-level function used by both sheet drag paths, and rewords its comment to say context.size throws in debug mode.

…er#196381) flutter/packages@08faf64...653628e 2026-11-11 [email protected] Roll Flutter from fffd8c2 to b98afb5 (31 revisions) (flutter/packages#13623) 2026-11-11 [email protected] [material_ui] Document how to programmatically clear DropdownMenu selection (flutter/packages#13266) 2026-11-11 [email protected] [pigeon] Fix basePath resolution when paths share a string prefix with basePath (flutter/packages#13342) 2026-11-11 [email protected] [cupertino_ui] Fix CupertinoSheetRoute throwing when a drag ends during a pending relayout (flutter/packages#13316) 2026-11-11 [email protected] [shared_preferences] Updates Pigeon to 30.0.1 to support multi-engine registration and deregistration. (flutter/packages#13617) 2026-11-11 [email protected] [vector_graphics] Catch any throwable in useHtmlRenderObject() and cache HTML fallback (flutter/packages#13545) 2026-11-11 [email protected] [cupertino_ui] Include selectionHandleColor in NoDefaultCupertinoThemeData equality (flutter/packages#13450) 2026-11-11 [email protected] [flutter_svg] Remove failed async loads from Cache._pending (flutter/packages#13604) 2026-11-11 [email protected] [pigeon] Adds Native Interop FFI codec serialization for NS types (flutter/packages#13616) 2026-11-10 [email protected] [pigeon] Support multi-engine Native Interop registration and instance-aware unregistration (flutter/packages#13576) 2026-11-10 [email protected] [image_picker_ios] Convert the iOS example app and UI tests to Swift (flutter/packages#13570) 2026-11-10 [email protected] [cupertino_ui] Localize CupertinoActionSheet semantics label (flutter/packages#13377) 2026-11-10 [email protected] [camera_android] Fix stopVideoRecording returning JPEG when takePicture runs during recording (flutter/packages#13070) 2026-11-10 [email protected] [google_sign_in_android] Rename keep.xml to google_sign_in_keep.xml (flutter/packages#13475) 2026-11-10 [email protected] [web_benchmarks] Fix benchmark stalling when only repainting views that are dirty (flutter/packages#13089) 2026-11-10 [email protected] Roll Flutter from d463821 to fffd8c2 (21 revisions) (flutter/packages#13614) If this roll has caused a breakage, revert this CL and set the roller to dry run mode using the controls here: https://autoroll.skia.org/r/flutter-packages-flutter-autoroll Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

github-actions Bot added p: cupertino_ui triage-design Should be looked at in design triage labels Oct 19, 2026

theprantadutta mentioned this pull request Oct 19, 2026

CupertinoSheetRoute asserts when a drag ends in the frame a relayout lands flutter/flutter#194681

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gemini-code-assist Bot reviewed Oct 19, 2026

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Read the sheet height once per drag update

4d2619a

Piinks requested a review from dkwingsmt October 20, 2026 21:25

Merge remote-tracking branch 'upstream/main' into cupertino_ui/sheet-…

862ba14

…drag-size-during-layout

dkwingsmt approved these changes Nov 10, 2026

View reviewed changes

dkwingsmt requested a review from pjkammer November 10, 2026 07:43

dkwingsmt reviewed Nov 10, 2026

View reviewed changes

Share one sheet height helper between both drag paths

babcf0b

Moves the render box height read into a top-level function used by both sheet drag paths, and rewords its comment to say context.size throws in debug mode.

dkwingsmt added the CICD Run CI/CD label Nov 10, 2026

pjkammer approved these changes Nov 11, 2026

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pjkammer added the autosubmit Merge PR when tree becomes green via auto submit App label Nov 11, 2026

auto-submit Bot merged commit 054d9d1 into flutter:main Nov 11, 2026
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This was referenced Nov 11, 2026

Roll Packages from 08faf6409187 to b9397f207c07 (15 revisions) flutter/flutter#196380

Closed

Roll Packages from 08faf6409187 to 653628e8a646 (16 revisions) flutter/flutter#196381

Merged

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[cupertino_ui] Fix CupertinoSheetRoute throwing when a drag ends during a pending relayout - #13316

[cupertino_ui] Fix CupertinoSheetRoute throwing when a drag ends during a pending relayout#13316
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theprantadutta commented Oct 19, 2026

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