[Windows] Fixed ItemSpacing doesn't work in Carousel View

[SubhikshaSf4851]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Root Cause:

CarouselView does not utilize the ItemSpacing property during layout styling

Description of Change

Added an item container style based on the horizontal or vertical orientation of the CarouselView, and applied a corresponding style to the ListViewBase

Issues Fixed

Fixes #29772

Tested the behaviour in the following platforms

• Windows
• Android
• iOS
• Mac

Screenshot

Before Issue Fix	After Issue Fix

[jsuarezruiz]

/azp run MAUI-UITests-public

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[jsuarezruiz]

/azp run MAUI-UITests-public

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Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull Request Overview

This PR enables ItemSpacing for CarouselView on Windows by applying an ItemContainerStyle and adjusting item size calculations, and adds a UI test to verify the fix.

• Added a host app page and shared UI test for Issue 29772
• Updated CarouselViewHandler.Windows to set container padding and account for ItemSpacing when measuring items

Reviewed Changes

Copilot reviewed 3 out of 6 changed files in this pull request and generated 3 comments.

File	Description
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29772.cs	Added a UI test for ItemSpacing but gated to iOS/Catalyst only
src/Controls/tests/TestCases.HostApp/Issues/Issue29772.cs	Host app page with a CarouselView setup, binding, and automation ID for testing ItemSpacing
src/Controls/src/Core/Handlers/Items/CarouselViewHandler.Windows.cs	Applied ItemContainerStyle and updated GetItemWidth/GetItemHeight to subtract spacing

[MauiBot]

🤖 AI Summary

📊 Expand Full Review — b692a87 · Implemented the suggested approach

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🔍 Pre-Flight — Context & Validation

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Issue: #29772 - ItemSpacing on CarouselView is not applied on Windows.
PR: #30014 - [Windows] Fixed ItemSpacing doesn't work in Carousel View
Platforms Affected: Windows (primary); Android/iOS/Mac also tested by author
Files Changed: 1 implementation, 2 test (+ 5 snapshot PNG files)

Key Findings

• LinearItemsLayout.ItemSpacing was being ignored on Windows in CarouselViewHandler; spacing was never applied to WinUI ListViewItem containers
• Fix approach: (1) New GetItemContainerStyle() creates a WStyle for ListViewItem with Control.PaddingProperty set to half-spacing on each side; (2) GetItemWidth()/GetItemHeight() unconditionally subtract ItemSpacing from item dimensions when orientation matches
• Current branch (b692a87) vs prior review commit (2ed72f7): The prior agent review (REQUEST CHANGES) flagged that ItemSpacing subtraction was gated on PeekAreaInsets > 0. That gate has been removed in the current branch — subtraction is now unconditional for matching orientation
• Dynamic update gap: GetItemContainerStyle() is called once at list creation; no mapper to re-apply style when ItemSpacing changes at runtime
• PlatformAffected.UWP in HostApp: [Issue(IssueTracker.Github, 29772, "...", PlatformAffected.UWP)] — should be PlatformAffected.All (cosmetic)
• CarouselViewShouldRenderCorrectly.png modified: An existing unrelated Windows snapshot was changed; PR description does not explain why
• Test uses VerifyScreenshot() with no [Platform] filter — runs on all platforms; Windows snapshot present
• Gate result: ✅ PASSED — tests FAIL without fix, PASS with fix (per task context)
• Prior agent review: s/agent-changes-requested + s/agent-fix-win were applied; PR has since been updated to address P1 issue

Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
PR	PR #30014	Add ItemContainerStyle with half-spacing padding on ListViewItem; unconditionally subtract ItemSpacing from item dimensions	✅ PASSED (Gate)	CarouselViewHandler.Windows.cs	P1 (gate) issue from prior review now fixed; dynamic update and UWP label remain

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🔧 Fix — Analysis & Comparison

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Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
1	try-fix (claude-opus-4.6)	Margin-based spacing: FrameworkElement.MarginProperty on ListViewItem with BasedOn style inheritance; unconditional ItemSpacing subtraction in GetItemWidth/GetItemHeight	✅ Pass	1 file	Margin creates gaps outside container; better semantic match for spacing between items
2	try-fix (claude-sonnet-4.6)	ItemContentControl.Margin via PropertyChangedCallback on existing ItemSpacingProperty; symmetric GetItemSpacing(); unconditional subtraction in GetItemWidth/GetItemHeight	✅ Pass	2 files	Activates existing data-binding infrastructure; no ItemContainerStyle at all
3	try-fix (gpt-5.3-codex)	ContainerContentChanging event handler to apply asymmetric ListViewItem.Padding per container	❌ Fail	1 file	5.22% visual diff — asymmetric padding produced inconsistent rendering
4	try-fix (gpt-5.4)	Runtime UpdateItemSpacing() method subscribed to LinearItemsLayout.ItemSpacing changes; reapplies Control.PaddingProperty style + invalidates item sizes dynamically	✅ Pass	1 file	Adds dynamic update support missing from PR; most complete solution
PR	PR #30014	Control.PaddingProperty on ListViewItem via ItemContainerStyle; unconditional ItemSpacing subtraction	✅ PASSED (Gate)	1 file	P1 gate issue from prior review addressed

Cross-Pollination

Model	Round	New Ideas?	Details
claude-opus-4.6	2	No	ItemsStackPanel has no Spacing property; panel-level approach not viable
gpt-5.4	2	No	Agrees viable approaches exhausted

Exhausted: Yes
Selected Fix: PR's fix — Gate ✅ PASSED; P1 issue (PeekAreaInsets gate) addressed; approach is valid. Attempt 4 shows a dynamic update path is feasible, but that is a P2 enhancement. Recommend PR approval with minor required changes.

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📋 Report — Final Recommendation

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✅ Final Recommendation: APPROVE

Phase Status

Phase	Status	Notes
Pre-Flight	✅ COMPLETE	Issue #29772 — Windows CarouselView ItemSpacing ignored
Gate	✅ PASSED	windows — tests FAIL without fix, PASS with fix
Try-Fix	✅ COMPLETE	4 attempts: 3 passing, 1 failing; cross-pollination exhausted
Report	✅ COMPLETE

Summary

The PR fixes ItemSpacing not being applied on Windows CarouselView. The root cause is correctly identified and the fix approach is valid. The primary concern from the prior agent review (spacing subtraction gated on PeekAreaInsets > 0) has been addressed in the updated PR — the subtraction is now unconditional for matching orientation. All try-fix alternatives passed confirm this is a viable fix space; the PR's approach is the simplest and most focused.

Root Cause

CarouselViewHandler.CreateCarouselListLayout() never applied any padding or margin to ListViewItem containers, so ItemSpacing had no visual effect on Windows. The existing GetItemSpacing() method was unused for container styling.

Fix Quality

What the PR does right:

• GetItemContainerStyle() correctly uses Control.PaddingProperty on ListViewItem with half-spacing per side, creating the visual gap
• GetItemWidth()/GetItemHeight() now unconditionally subtract ItemSpacing when orientation matches — the P1 gate issue from the prior review is fixed
• ItemContainerStyle applied at list creation for both horizontal and vertical orientations
• UI test with Windows snapshot present; gate confirms it validates the fix

Minor issues (non-blocking):

1. GetItemContainerStyle() only called at list creation (P2): If ItemSpacing changes at runtime, the ItemContainerStyle won't update. Try-Fix attempt 4 showed a dynamic subscription approach is feasible. This is an acceptable known limitation for this PR scope.
2. PlatformAffected.UWP in HostApp (P3 — cosmetic): [Issue(IssueTracker.Github, 29772, "...", PlatformAffected.UWP)] — modern MAUI uses PlatformAffected.All for Windows. Cosmetic only.
3. CarouselViewShouldRenderCorrectly.png modified (P2): An existing unrelated Windows snapshot changed; PR description doesn't explain why. Should be verified to confirm the fix didn't regress the existing test.

Try-Fix Comparison

Approach	Files	Result	Notes
PR's fix	1	✅ Gate	Control.PaddingProperty + unconditional subtraction
Margin-based (attempt 1)	1	✅ Pass	FrameworkElement.MarginProperty — semantically different
ItemContentControl callback (attempt 2)	2	✅ Pass	Activates existing binding chain
Asymmetric padding (attempt 3)	1	❌ Fail	5.22% visual diff
Dynamic update (attempt 4)	1	✅ Pass	Adds runtime reactivity

Selected Fix: PR's fix — simplest single-file change, gate validated, P1 correctness issue resolved.

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[kubaflo]

Could you please review the AI's summary?

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://github.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 30014

Or

• Run remotely in PowerShell:

iex "& { $(irm https://github.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 30014"

[kubaflo]

The test is passing without a fix

[SubhikshaSf4851]

@kubaflo The gate-without-fix check passed incorrectly because old baseline snapshots used a red background, masking the ItemSpacing difference.

Now the baselines have been updated to green background. With corrected snapshots, the test will now fail without the fix

[kubaflo]

/azp run maui-pr-uitests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[kubaflo]

Could you please try:
Selected Fix: Attempt 4 approach — keep PR's Control.PaddingProperty ItemContainerStyle, remove PeekAreaInsets gate from GetItemWidth/GetItemHeight. Simplest, least invasive change that is provably correct.

[SubhikshaSf4851]

@kubaflo I have implemented the suggested approach

[sheiksyedm]

/azp run maui-pr-uitests

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Azure Pipelines successfully started running 1 pipeline(s).