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Allow a zero scale change in InteractiveViewer - #194949
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_matrixScale asserted that the scale change is not 0.0. A pinch that moves both pointers to one point, a trackpad pan-zoom, or a PointerScaleEvent can give a scale change of 0.0. The clamp to minScale and maxScale that follows already gives a valid matrix for this value. Fixes flutter#82115
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This pull request removes the assert(scale != 0.0); statement from _InteractiveViewerState in interactive_viewer.dart. Additionally, it introduces two regression tests in interactive_viewer_test.dart to ensure that pinching both pointers to the same point and receiving a scale pointer event with a scale of 0.0 do not trigger exceptions. No review comments were provided for this pull request.
navaronbracke
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Oct 21, 2026
navaronbracke
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victorsanni
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LGTM pending review from Justin who wrote InteractiveViewer.
Use an infinite boundaryMargin and minScale 0.1, so the clamp to minScale is the active guard. Expect the exact end scale of 0.1.
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Roll Flutter from 3623d2d34543 to 09175cdeac89 (61 revisions) flutter/flutter@3623d2d...09175cd 2026-11-06 [email protected] Roll Skia from ae35b7b2221f to 793b8ac73d4b (3 revisions) (flutter/flutter#196091) 2026-11-06 [email protected] [web] Rasterize scenes at the size passed to `FlutterView.render` (flutter/flutter#196052) 2026-11-06 [email protected] Roll Skia from 4aa043a81e0c to ae35b7b2221f (1 revision) (flutter/flutter#196086) 2026-11-06 [email protected] Roll Fuchsia Linux SDK from Fqe3UlLwAohsPbsCS... to KIc0XZbhLmvDpTluZ... (flutter/flutter#196085) 2026-11-06 [email protected] Allow a zero scale change in InteractiveViewer (flutter/flutter#194949) 2026-11-06 [email protected] Roll Skia from dd5c2553a856 to 4aa043a81e0c (2 revisions) (flutter/flutter#196079) 2026-11-06 [email protected] [web] Keep ImageFilter.blur bounds in equality and description (flutter/flutter#196013) 2026-11-06 [email protected] iOS: Remove unused PlatformViewIOS setup from FlutterPlatformViewsTest (flutter/flutter#196033) 2026-11-06 [email protected] Serialize LoggerTests that mutate the shared Logger (flutter/flutter#196028) 2026-11-06 [email protected] Use reverseDuration for the AnimatedCrossFade size animation (flutter/flutter#194860) 2026-11-05 [email protected] Roll Skia from a5aacd103e68 to dd5c2553a856 (8 revisions) (flutter/flutter#196073) 2026-11-05 [email protected] Fix ListWheelScrollView null check error when it reads itemIndex before content dimensions are set (flutter/flutter#194859) 2026-11-05 [email protected] Allow zero cross axis extent in SliverGridDelegateWithMaxCrossAxisExtent (flutter/flutter#194858) 2026-11-05 [email protected] Revert: Allow color delta tolerance in in-memory fuzzy image comparator (flutter/flutter#196067) 2026-11-05 [email protected] Revert: Mitigate snapshot race in 3D transform test by reducing loop density (flutter/flutter#196066) 2026-11-05 [email protected] Delegate createStream in ResizeImage and ScrollAwareImageProvider (flutter/flutter#194756) 2026-11-05 [email protected] [iOS] Introduce FlutterShell and move thread host and profiler (flutter/flutter#195388) 2026-11-05 [email protected] [web] Support FragmentShader.getImageSampler on CanvasKit and Skwasm (flutter/flutter#195854) 2026-11-05 [email protected] Deprecates setFloat API (flutter/flutter#195505) 2026-11-05 [email protected] [flutter_tools] Remove public GlobalToolContext and globals from runner (flutter/flutter#195561) 2026-11-05 [email protected] Defer TLHC PlatformViewWrapper frame post and avoid initial 1x1 buffer resize (flutter/flutter#195861) 2026-11-05 [email protected] Roll Skia from b5abed66da86 to a5aacd103e68 (17 revisions) (flutter/flutter#196054) 2026-11-05 [email protected] Made `FlutterWindowControllerSizeTest.SizedToContentNotResizable` more robust (flutter/flutter#195845) 2026-11-05 [email protected] Update docs for contributor ladder (flutter/flutter#196011) 2026-11-05 [email protected] [Impeller] Use the transfer stage for the Vulkan readback barrier (flutter/flutter#194991) 2026-11-05 [email protected] Remove Mac mac_unopt builder (flutter/flutter#196027) 2026-11-05 [email protected] Updated Instructions for Determining Gradle Version for `gradle_dists` in CIPD (flutter/flutter#193310) 2026-11-05 [email protected] Move ios_app_with_extensions_test into the tool integration shard (flutter/flutter#195609) 2026-11-05 [email protected] [web] Respect Uint8List view bounds when detecting animated WebP/GIF (flutter/flutter#196010) 2026-11-05 [email protected] Add platform_views_layout to build_tests so iOS/Android build breaks are caught in presubmit (flutter/flutter#192985) 2026-11-05 [email protected] [flutter_tools] Detect macOS TCC permission crashes and provide diagnostic guidance (flutter/flutter#192432) 2026-11-05 [email protected] Roll Packages from 670b30e to 0478162 (15 revisions) (flutter/flutter#196047) 2026-11-05 [email protected] [web] Support Skwasm rendering without bitmap capture (flutter/flutter#195103) 2026-11-05 [email protected] [flutter_tools] Reland fix for local CanvasKit asset paths on Windows (flutter/flutter#195770) 2026-11-05 [email protected] Roll Skia from f96be51af95d to b5abed66da86 (14 revisions) (flutter/flutter#196017) 2026-11-05 [email protected] Split chrome web engine test drone (flutter/flutter#195873) 2026-11-05 [email protected] Roll Dart SDK from c9153304136a to 6623b84628f3 (1 revision) (flutter/flutter#196026) 2026-11-05 [email protected] Roll ICU from 4fe960221710 to a0ea93436c52 (6 revisions) (flutter/flutter#196025) 2026-11-05 [email protected] Add more guidance in README and AGENTS for contributing to flutter_tools (flutter/flutter#195998) 2026-11-05 [email protected] Roll Fuchsia Linux SDK from p0HDXLISPIElJfSz7... to Fqe3UlLwAohsPbsCS... (flutter/flutter#196019) 2026-11-05 [email protected] Roll Dart SDK from e362a23e9738 to c9153304136a (18 revisions) (flutter/flutter#196014) 2026-11-05 [email protected] [Impeller] Fix dilation input bounds when clipping saveLayers (flutter/flutter#195652) 2026-11-05 [email protected] Add `variantOf` to the M3E migration checklist (flutter/flutter#195099) 2026-11-05 [email protected] [flutter_tools] Eliminate globals from remaining subsystem files (flutter/flutter#195555) 2026-11-05 [email protected] Fix gap flipping when dragging variable height reorderable items (flutter/flutter#194478) 2026-11-05 [email protected] [A11y] Send un-merged SemanticsNodes in the same update that first references them (flutter/flutter#195829) ...
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InteractiveViewerassertsscale != 0.0in_matrixScale. Some inputs give a scale change of 0.0, and then the assert fails. These inputs reach a scale change of 0.0:ScaleUpdateDetails.scaleis then 0.0. A pointer distance of 1e-300 also gives 0.0, because the coordinates round to the same value.PointerScaleEventwith a scale of 0.0.scrollDelta.dy, or with a very smallscaleFactor. Thenmath.exp(-event.scrollDelta.dy / widget.scaleFactor)underflows to 0.0.trackpadScrollCausesScale: trueand a very large delta.All of these inputs go through
_matrixScale.The code after the assert already handles a scale change of 0.0. It clamps the total scale with
clampDouble(totalScale, widget.minScale, widget.maxScale), and the constructor assertsminScale > 0. Thus, the new scale is at leastminScale, and the matrix values stay finite. The assert does not stop a negative scale change. Before this change,PointerScaleEvent(scale: -1)already went through the same clamp with no error. A scale change of 0.0 follows the same path.This PR removes the assert. For a scale change that is not 0.0, the behavior does not change.
Fixes #82115
Tests
I added two regression tests to
packages/flutter/test/widgets/interactive_viewer_test.dart. They use two different input paths to_matrixScale:PointerScaleEventwith a scale of 0.0. This input goes through the pointer signal handler.Each test makes sure that no exception occurs, that all matrix values are finite, and that the scale is more than 0.0.
test/widgets'scale != 0.0': is not true(interactive_viewer.dartline 647)interactive_viewer_test.dart: +62, all tests passed)The 1 failure also occurs on the base commit without this change. It is
ext.flutter.inspector.screenshotinwidget_inspector_test.dart, and it depends on the local environment.Pre-launch Checklist
///). No doc change is necessary.test/widgetstests pass locally, except one test that also fails on the base commit. The other tests run only in CI.If you need help, consider asking for advice on the #hackers-new channel on Discord.