Fix unexpected shown of Scrollbar #159386

hgraceb · 2024-11-24T08:59:45Z

Fixes Narrow DatePickerDialog has unnecessary scrollbar on months with 6 rows #141348

Details

288 / 7 + 288 / 7 * 6 = 288.00000000000006

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

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victorsanni

LGTM. cc @nate-thegrate who fixed a similar problem recently in NestedScrollView.

Piinks · 2024-12-03T23:16:10Z

packages/flutter/lib/src/widgets/scrollbar.dart

@@ -516,8 +516,7 @@ class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
    _lastMetrics = metrics;
    _lastAxisDirection = axisDirection;

-    bool needPaint(ScrollMetrics? metrics) => metrics != null && metrics.maxScrollExtent > metrics.minScrollExtent;


Removing this public method would be a breaking change, can you revert that?

Much like in a previous PR by @hgraceb, the narrow GitHub diffs make it kinda difficult to see the context of this change. Fortunately this is a local function defined inside the ScrollbarPainter.update method, so I believe we're good 👍

As @nate-thegrate said, thanks for the explanation.

Oh it is indeed! Sorry I did not catch that! :)

nate-thegrate

One of the few things I remember from college is the huge potential for precision loss when evaluating the difference between two numbers that are very close together.

I also remember how difficult it was for me to figure out what was going wrong while working on #157756.

Thanks for catching this and implementing the fix!

nate-thegrate · 2024-12-04T01:00:31Z

packages/flutter/lib/src/widgets/scrollbar.dart

@@ -516,8 +516,7 @@ class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
    _lastMetrics = metrics;
    _lastAxisDirection = axisDirection;

-    bool needPaint(ScrollMetrics? metrics) => metrics != null && metrics.maxScrollExtent > metrics.minScrollExtent;


Much like in a previous PR by @hgraceb, the narrow GitHub diffs make it kinda difficult to see the context of this change. Fortunately this is a local function defined inside the ScrollbarPainter.update method, so I believe we're good 👍

victorsanni · 2024-12-05T00:00:11Z

I'm investigating the google testing failures. I haven't looked too deeply but this change might be causing an issue with horizontal scrollbars.

hgraceb · 2024-12-11T09:46:29Z

I'm investigating the google testing failures. I haven't looked too deeply but this change might be causing an issue with horizontal scrollbars.

Is there any update or more information?

victorsanni · 2024-12-11T18:56:15Z

Is there any update or more information?

Still trying to reproduce. But the tests pass if I lower precisionErrorTolerance from 1e-10 to 1e-14.

victorsanni · 2024-12-17T23:38:28Z

@hgraceb this test in data_table_2 fails due to the changes in this PR:

https://github.com/maxim-saplin/data_table_2/blob/ceacea5279769fcd35b01e01f3eb21207c6fea61/test/custom_features_test.dart#L27

hgraceb · 2024-12-18T14:17:19Z

@victorsanni I can confirm that this test failed because it was written with an incorrect expected result. If you change the width from 250 to 250 + precisionErrorTolerance or 250 + 1e-10, this test will fail even without the changes from the current PR.

 testWidgets(
     'Horizontal scrollbar is visible if isHorizontalScrollBarVisible=true',
     (WidgetTester tester) async {
   await wrapWidgetSetSurf(tester,
-      buildTable(isHorizontalScrollBarVisible: true), const Size(250, 300));
+      buildTable(isHorizontalScrollBarVisible: true), const Size(250 + precisionErrorTolerance, 300));
 
   await tester.pumpAndSettle();
 
   expect(find.byType(Scrollbar).first, paints..rect());
 });

victorsanni · 2025-01-27T18:55:15Z

Hi @hgraceb, thanks for your patience. We're currently working on a patch to apply the fixes you proposed to the failing google tests, and will move forward with merging this PR once that work is done.

victorsanni · 2025-01-29T17:58:52Z

Hi @hgraceb, this PR has some merge conflicts. Once they are fixed, google testing should pass when rerun.

hgraceb · 2025-01-30T11:25:59Z

Hi @victorsanni, the Google tests are still failing. Are there any other unit tests that are broken?

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goderbauer requested a review from victorsanni November 26, 2024 23:04

victorsanni approved these changes Dec 3, 2024

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victorsanni requested a review from nate-thegrate December 3, 2024 21:34

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hgraceb mentioned this pull request Dec 19, 2024

Fix the erroneous scrollbar tests maxim-saplin/data_table_2#330

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hgraceb mentioned this pull request Jan 22, 2025

Scrollbar test written based on incorrect behavior maxim-saplin/data_table_2#344

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Fix unexpected shown of Scrollbar

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Fix unexpected shown of Scrollbar #159386

Fix unexpected shown of Scrollbar #159386

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hgraceb commented Nov 24, 2024

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