Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change #29639

albyrock87 · 2025-05-23T11:50:28Z

Description of Change

GridViewLayout has a special positioning override when there's only one item.

if (ScrollDirection == UICollectionViewScrollDirection.Vertical && NeedsSingleItemHorizontalAlignmentAdjustment(layoutAttributesForRectElements))
{
	// If there's exactly one item in a vertically scrolling grid, for some reason UICollectionViewFlowLayout
	// tries to center it. This corrects that issue.
	var currentFrame = layoutAttributesForRectElements[0].Frame;
	var newFrame = new CGRect(CollectionView.Frame.Left + CollectionView.ContentInset.Right,
	currentFrame.Top, currentFrame.Width, currentFrame.Height);
	layoutAttributesForRectElements[0].Frame = newFrame;
}

So we have to invalidate the layout entirely to trigger that special case, instead of just simply invalidate single cells.

Issues Fixed

Fixes #29595
Fixes #29634

rmarinho

I think we just need to update the screenshot.

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29595_29634.cs

rmarinho · 2025-05-27T18:07:11Z

@albyrock87 seems theres still a slight difference, I wonder if we should change the threshold of the comparison .

VisualTestUtils.VisualTestFailedException :
Snapshot different than baseline: VerifyGridItemsLayoutSingleAndEmptyViewResize.png (0.50% difference)
If the correct baseline has changed (this isn't a a bug), then update the baseline image.
See test attachment or download the build artifacts to get the new snapshot file.

mattleibow

Thanks for the PR, I have a few questions:

I am not seeing a visible difference in the final logic of the CV2 code
Similar with CV1 - except for a final if and layout all
The tests is very complex and I am not sure what we are testing
The PR has a fix for 2 things, but there is only 1 test
The CV code has logic for horizontal and vertical grids, should we add tests for each
Does this just manifest if the items change after the page loads, or also on the page init? Should we cover both cases?

mattleibow · 2025-05-30T20:57:15Z

src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewController2.cs

-			List<NSIndexPath> invalidatedPaths = null;
+			List<TemplatedCell2> invalidatedCells = null;


Why did this have to change? I see before we get the index and store it here, then invalidate. Now you get the cell, store it, and then later get the index.

Does this different path do different things? Looks like in the end you still use the same cell index in the invalidate.

I wanted to avoid a reference to NS objects when possible.

mattleibow · 2025-05-30T21:01:05Z

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewController.cs

+				if (ItemsSource.ItemCount == 1)
+				{
+					CollectionView.CollectionViewLayout.InvalidateLayout();
+				}


Is this extra code path not needed in CV2?

mattleibow · 2025-05-30T21:10:09Z

src/Controls/tests/TestCases.HostApp/Issues/Issue29595_29634.cs

+using System.Windows.Input;
+using Microsoft.Maui.Controls.Shapes;
+
+namespace Maui.Controls.Sample.Issues


This test is really complex and there are many things here. Does this issue not repro in a case without all of this special work?

I see multiple collection views, shell, pages, tabs and all sorts of delay things.

Can this not be broken into a simple test where the page loads and then the UI test taps a button to add an item if we need things loaded later.

Also, the fix for the empty view has no tests I think?

…t left aligning single item

src/Controls/tests/TestCases.HostApp/Issues/Issue29634.cs

PureWeen · 2025-06-19T20:17:26Z

/azp run

azure-pipelines · 2025-06-19T20:17:48Z

Azure Pipelines successfully started running 3 pipeline(s).

PureWeen · 2025-06-20T16:23:20Z

/azp run MAUI-UITests-public

azure-pipelines · 2025-06-20T16:23:33Z

Azure Pipelines successfully started running 1 pipeline(s).

PureWeen · 2025-06-21T12:09:50Z

/backport to release/9.0.1xx-sr8

github-actions · 2025-06-21T12:09:58Z

Started backporting to release/9.0.1xx-sr8: https://github.com/dotnet/maui/actions/runs/15795546965

…resizing when bounds change (#29639) * Fix CV1 empty view not resizing when bounds change and grid layout not left aligning single item * - rework test * - fix test --------- Co-authored-by: Shane Neuville <shneuvil@microsoft.com>

@kubaflo

For more information about inflight process check https://github.com/dotnet/maui/wiki/Inflight-Branch-Process # .NET MAUI Release Notes - Inflight/Candidate Branch ## What's Changed ### MAUI Product Fixes * [iOS] CarouselView with CarouselViewHandler2 make app crash when Loop="False" and user scroll to the last position - fixes #26863 by @kubaflo in #26868 * Fixes Setting BackgroundColor to null does not actually changes BackgroundColor - fixes #22914 and #19576 by @jgonzalez-gft in #22917 * Fixed the picker title's color - fixes #16737 by @kubaflo in #23075 * [android] Fallback to default icons in SearchHandler by @aheubusch in #25067 * ScrollView's Background on iOS - fixes #24016 by @kubaflo in #25541 * [iOS] Enabled MultiTouch Support for Handling Multi-Touch Points in GraphicsView - fixes #29461 by @prakashKannanSf3972 in #29895 * Optimize converters for GridLength, ColumnDefinition, and RowDefinition - performance improvement by @emiller in #20048 * Add defensive IsAlive check to Android ViewExtensions.OnUnloaded - fixes #28051 by @jfversluis in #29934 * [Windows] Fixed runtime update issue for SearchBar PlaceholderColor and BackgroundColor - fixes #29962 by @Tamilarasan-Paranthaman in #29965 * Weak subscription to CanExecuteChange events - fixes #16124 by @sneumaier in #29837 * [iOS, Mac] Fix for downsized image retaining original dimensions in GraphicsView - fixes #30006 by @SyedAbdulAzeemSF4852 in #30007 * [Android] Prevent Picker from Gaining Focus on Touch - fixes #19739, #8546, #13503, #24862, #28121, #21704, #15394 by @bhavanesh2001 in #29068 * Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change - fixes #29595, #29634 by @albyrock87 in #29639 ### Testing * [Testing] Feature Matrix UITest Cases for Button by @TamilarasanSF4853 in #29803 * [Testing] Feature matrix UITest Cases for BoxView Control by @HarishKumarSF4517 in #29808 * [Testing] Enable HandlerDoesNotLeak for Button and ProgressBar by @bhavanesh2001 in #29896 * [Testing] Add Validation Test For Issue28051 On Android by @prakashKannanSf3972 in #30026 * [Testing] Fixed Test case failure in PR 30115 - [2025/06/23] Candidate by @HarishKumarSF4517 in #30136 ### Dependency Updates * Bump to 1.7.250606001 of WindowsAppSDK by @sneumaier in #29915 ### Housekeeping * [housekeeping] Update namespaces in HostApp and Shared tests projects by @bhavanesh2001 in #29904 * Update SetterSpecificity.cs Remove Extra Line From Bad Merge by @sneumaier in #29987 * Revert - Fixed the Label not sized correctly on Android by @Ahamed-Ali in #30023 * Revert "Fixes Setting BackgroundColor to null does not actually changes BackgroundColor #22914 (#22917)" by @mattleibow in #30031 * [create-pull-request] automated change by @github-actions[bot] in #30019 * [create-pull-request] automated change by @github-actions[bot] in #30043 * [create-pull-request] automated change by @github-actions[bot] in #30078 * Update Controls.TestCases.HostApp.csproj by @HarishKumarSF4517 in #30124 ## New Contributors * @albyrock87 made their first contribution in #29639 * @SyedAbdulAzeemSF4852 made their first contribution in #30007 * @emiller made their first contribution in #20048 * @jgonzalez-gft made their first contribution in #22917 * @aheubusch made their first contribution in #25067 **Full Changelog**: https://github.com/dotnet/maui/compare/main..inflight/candidate

albyrock87 requested a review from a team as a code owner May 23, 2025 11:50

albyrock87 requested review from PureWeen and jsuarezruiz May 23, 2025 11:50

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albyrock87 force-pushed the fix-29595 branch from b72cfa1 to b44f21a Compare May 23, 2025 14:30

albyrock87 changed the title ~~Fix CV1 GridLayout special behavior~~ Fix CV1 GridItemsLayout not centering single item, Empty view not resizing when bounds change May 23, 2025

jsuarezruiz added the area-controls-collectionview CollectionView, CarouselView, IndicatorView label May 26, 2025

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mattleibow changed the title ~~Fix CV1 GridItemsLayout not centering single item, Empty view not resizing when bounds change~~ Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change May 30, 2025

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PureWeen added p/0 Work that we can't release without p/1 Work that is important, and has been scheduled for release in this or an upcoming sprint and removed p/0 Work that we can't release without labels Jun 2, 2025

albyrock87 force-pushed the fix-29595 branch 2 times, most recently from 6ebf2cb to ca9132b Compare June 5, 2025 11:08

Fix CV1 empty view not resizing when bounds change and grid layout no…

da55e18

…t left aligning single item

PureWeen added this to the .NET 9 SR9 milestone Jun 9, 2025

PureWeen requested review from mattleibow and rmarinho June 9, 2025 23:29

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- rework test

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- fix test

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PureWeen approved these changes Jun 21, 2025

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PureWeen changed the base branch from main to inflight/current June 21, 2025 12:09

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[release/9.0.1xx-sr8] Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change #30107

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[2025/06/23] Candidate - In Flight Branch #30115

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Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change #29639

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		List<NSIndexPath> invalidatedPaths = null;
		List<TemplatedCell2> invalidatedCells = null;

Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change #29639

Fix CV1 GridItemsLayout centering single item AND Fix Empty view not resizing when bounds change #29639

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Description of Change

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