[iOS] Fix ScrollView with RTL FlowDirection and Horizontal Orientation scrolls in the wrong direction

[devanathan-vaithiyanathan]

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!

Issue Details

When a ScrollView is set to RightToLeft (RTL) flow direction and its Orientation is changed at runtime, the scrolling behavior is not working on iOS.

Description of Change

Added orientation tracking and enabled the logic to perform RTL layout handling during cross-platform arrange.

Issues Fixed

Fixes #32271

Tested the behavior in the following platforms.

• Android
• Windows
• iOS
• Mac

Before	After
iOS Before.mov	iOS After.mov

[Copilot]

Pull Request Overview

This PR fixes an iOS-specific issue where ScrollView with RTL (Right-To-Left) FlowDirection fails to scroll correctly when the Orientation property is changed at runtime from Vertical to Horizontal. The fix adds orientation change tracking to ensure RTL layout adjustments are properly recalculated.

Key changes:

• Added OnOrientationChanged() method to MauiScrollView to reset RTL layout state
• Updated MapOrientation handler to call OnOrientationChanged() when orientation changes at runtime
• Added UI test coverage with Issue32271 test case

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/Core/src/Platform/iOS/MauiScrollView.cs	Adds OnOrientationChanged() method to reset cached RTL layout direction and trigger re-layout when orientation changes
src/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cs	Calls OnOrientationChanged() in MapOrientation when the platform view is loaded to handle runtime orientation changes
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs	Adds NUnit test that toggles orientation and verifies scrolling behavior via screenshot
src/Controls/tests/TestCases.HostApp/Issues/Issue32271.cs	Adds test host page with RTL ScrollView that supports runtime orientation toggling and scroll-to commands

[rmarinho]

🤖 AI Summary

📊 Expand Full Review

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🔍 Pre-Flight — Context & Validation

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📝 Review Session — Update Issue32271.cs · dc92906

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Issue: #32271 - ScrollView with RTL FlowDirection and Horizontal Orientation scrolls in the wrong direction on iOS
PR: #32529 by @devanathan-vaithiyanathan (Syncfusion partner)
Platforms Affected: iOS only
Files Changed: 2 implementation files, 2 test files

Issue Summary

When a ScrollView is set to FlowDirection = RightToLeft and its Orientation is changed at runtime (Vertical → Horizontal), the RTL scrolling logic in MauiScrollView.CrossPlatformArrange() is not re-applied. The RTL layout block is gated on _previousEffectiveUserInterfaceLayoutDirection != EffectiveUserInterfaceLayoutDirection, which after the initial layout pass evaluates to RTL != RTL (false), so it never fires again even when orientation changes. The result: the content can only be scrolled into empty space instead of the correct RTL direction.

Expected: Dragging right-to-left reveals content on the right side
Actual: Scroll direction is reversed; scrolling into empty space

Prior Agent Review (Same Commit dc92906)

A prior agent review exists from the same commit dc92906. Labels: s/agent-changes-requested, s/agent-gate-failed, s/agent-fix-pr-picked.

• Pre-Flight: COMPLETE
• Gate: FAILED (missing VerifyScreenshot baseline snapshot)
• Fix: SKIPPED (rate limit), code analysis confirms fix is correct
• Report: REQUEST CHANGES (baseline snapshot missing)

Reviewer Feedback

File:Line	Reviewer Says	Status
MauiScrollView.cs:113	Check EffectiveUserInterfaceLayoutDirection == RTL instead of _previousEffectiveUserInterfaceLayoutDirection == RTL	🔍 ANALYZED - NOT A REAL BUG (see Fix phase)
TestCases.HostApp/Issues/Issue32271.cs	Orientation mismatch between ScrollView declaration and ViewModel	✅ FIXED (commit dc92906, thread is Outdated)

Files Changed

Implementation (Fix):

• src/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cs (+8) — Calls mauiScrollView.OnOrientationChanged() in MapOrientation when view is loaded
• src/Core/src/Platform/iOS/MauiScrollView.cs (+14) — Adds OnOrientationChanged() method that resets _previous to null and forces layout

Tests:

• src/Controls/tests/TestCases.HostApp/Issues/Issue32271.cs (+146) — UI test host page with RTL ScrollView + Toggle Orientation button
• src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs (+20) — NUnit test: tap Toggle → tap Scroll → VerifyScreenshot

Test Type: UI Tests (Appium-based, VerifyScreenshot)

Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
PR	PR #32529	Reset _previousEffectiveUserInterfaceLayoutDirection to null in OnOrientationChanged(), force layout	⏳ PENDING (Gate)	ScrollViewHandler.iOS.cs (+8), MauiScrollView.cs (+14)	Logic analyzed as correct

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🚦 Gate — Test Verification

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📝 Review Session — Update Issue32271.cs · dc92906

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Result: ❌ FAILED
Platform: ios
Mode: Full Verification

• Tests FAIL without fix ✅ (expected - bug detected)
• Tests PASS with fix ❌ (unexpected - fix doesn't resolve test)

Root Cause of Gate Failure

The test VerifyScrollViewDirection() calls VerifyScreenshot() which requires a committed baseline snapshot file. No baseline exists in the repository:

src/Controls/tests/TestCases.iOS.Tests/snapshots/ios/VerifyScrollViewDirection.png

(or similar path — file does not exist)

Both test runs (with and without fix) fail because the snapshot infrastructure cannot find a baseline to compare against. This is NOT a bug in the fix — the build succeeds and the fix is logically correct. The test cannot pass until the PR author:

1. Runs the test locally on iOS to generate the baseline snapshot
2. Commits the baseline snapshot PNG to the repository

Note

This is the SECOND review on the same commit dc92906. The prior agent review (prior run, same commit) also failed Gate for this same reason. The PR author has not yet addressed the missing baseline.

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🔧 Fix — Analysis & Comparison

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📝 Review Session — Update Issue32271.cs · dc92906

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Fix Candidates

#	Source	Approach	Test Result	Files Changed	Notes
PR	PR #32529	Reset _previousEffectiveUserInterfaceLayoutDirection to null via OnOrientationChanged() when orientation changes at runtime; force layout via SetNeedsLayout() + LayoutIfNeeded()	❌ NOT VERIFIED (Gate baseline missing)	ScrollViewHandler.iOS.cs (+8), MauiScrollView.cs (+14)	Code analysis confirms logic is correct (see below)

Exhausted: No (Fix phase skipped — Gate did not pass)

Selected Fix: PR's fix — Code analysis (below) confirms the approach is logically sound.

Code Analysis of PR's Fix

Root cause: In MauiScrollView.CrossPlatformArrange() (line 486), the RTL content offset logic is gated on:

if (_previousEffectiveUserInterfaceLayoutDirection != EffectiveUserInterfaceLayoutDirection)

After the initial layout pass, _previous = RightToLeft. On subsequent layout passes (even after orientation change), RTL != RTL evaluates to false — the RTL positioning is never re-applied for the new orientation dimensions.

Fix logic (OnOrientationChanged):

if (_previousEffectiveUserInterfaceLayoutDirection == UIUserInterfaceLayoutDirection.RightToLeft)
{
    _previousEffectiveUserInterfaceLayoutDirection = null;    // Reset to force re-evaluation
    SetNeedsLayout();
    LayoutIfNeeded();                                         // Synchronous layout pass
}

Setting _previous = null makes the condition null != RTL → true, forcing the RTL layout block to execute for the new orientation dimensions.

Correctness trace (repeated toggles):

1. Initial (RTL, Horizontal): null != RTL → RTL layout applied → _previous = RTL ✅
2. Toggle to Vertical: OnOrientationChanged() → _previous = null → layout pass → null != RTL → RTL layout applied → _previous = RTL ✅
3. Toggle back to Horizontal: OnOrientationChanged() → _previous = RTL (TRUE) → _previous = null → layout pass → null != RTL → RTL layout applied → _previous = RTL ✅
4. Repeated toggles: same pattern ✅

Copilot reviewer's suggestion analysis: The Copilot reviewer suggested changing the condition to EffectiveUserInterfaceLayoutDirection == RightToLeft. This concern is based on an incorrect assumption that _previous becomes null after step 2 and stays null. In reality, the LayoutIfNeeded() call in OnOrientationChanged() triggers ArrangeContent() which sets _previous = RTL before returning. So on step 3, _previous == RTL is TRUE and the fix works correctly. The Copilot suggestion is not needed.

Minor concerns:

• Double layout pass: OnOrientationChanged() calls LayoutIfNeeded() synchronously, then MapOrientation calls InvalidateMeasure(). Minor performance cost for complex layouts.
• No platform guard on NUnit test: PlatformAffected.iOS in HostApp page but test has no [Ignore] for other platforms.

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📋 Report — Final Recommendation

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📝 Review Session — Update Issue32271.cs · dc92906

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⚠️ Final Recommendation: REQUEST CHANGES

Summary

PR #32529 fixes a real and confirmed iOS bug where a ScrollView with FlowDirection = RightToLeft loses its RTL scrolling behavior after the Orientation is changed at runtime. The fix approach is logically sound and minimal. However:

1. [Blocking] The VerifyScrollViewDirection test calls VerifyScreenshot() but no baseline snapshot has been committed to the repository — the test will fail in CI on every run until this is added.
2. [Non-blocking] The Copilot reviewer's inline suggestion at MauiScrollView.cs:113 has NOT been addressed (still open/unresolved), though code analysis confirms the suggestion is actually not needed (see analysis below).
3. [Minor] The Issue32271.cs NUnit test file is missing a newline at end of file.
4. [Minor] The NUnit test has no platform guard, but the HostApp page declares PlatformAffected.iOS.

This is the second agent review on the same commit (dc92906). The prior review also failed Gate for the identical reason. The PR author has not yet addressed the missing baseline.

Root Cause

In MauiScrollView.CrossPlatformArrange(), the RTL content offset logic is protected by:

if (_previousEffectiveUserInterfaceLayoutDirection != EffectiveUserInterfaceLayoutDirection)

After the initial layout pass sets _previous = RightToLeft, this condition always evaluates to false on subsequent passes — the RTL positioning is never re-applied when orientation changes (which changes content dimensions, requiring a new offset calculation).

Fix Analysis

PR's Approach: Add OnOrientationChanged() to MauiScrollView that resets _previousEffectiveUserInterfaceLayoutDirection = null (when it was RTL), then calls SetNeedsLayout() + LayoutIfNeeded() to synchronously re-trigger the RTL layout block.

Is the fix correct? Yes. The logic handles repeated orientation toggles correctly:

• After each toggle, LayoutIfNeeded() restores _previous = RTL before the method returns
• So on the next toggle, _previous == RTL is always true → the reset works for all subsequent toggles

Copilot reviewer's suggestion: The suggestion to change the condition to EffectiveUserInterfaceLayoutDirection == RightToLeft is based on an incorrect assumption that _previous stays null after a toggle. In reality, ArrangeContent() (called by LayoutIfNeeded()) sets _previous = RTL before returning. The original PR's condition is functionally equivalent for the bug scenario. The suggestion is NOT required.

Issues Requiring Changes

[Blocking] Missing baseline snapshot for VerifyScrollViewDirection test

Evidence from Gate: Both test runs (WITH and WITHOUT fix) failed because the baseline snapshot does not exist:

• src/Controls/tests/TestCases.iOS.Tests/snapshots/ios/VerifyScrollViewDirection.png — MISSING

Required action:

1. Run the test locally on iOS to generate the baseline screenshot
2. Commit the baseline PNG to the PR branch
3. See visual test workflow

[Minor] Missing newline at EOF

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs — no newline at end of file.

[Minor] NUnit test runs on all platforms but HostApp page is iOS-only

The NUnit test has no [Category] or [Ignore] to restrict it to iOS, while Issue32271 : ContentPage declares PlatformAffected.iOS. This may cause failures on other platforms if the test infrastructure can't find the page.

Phases Completed

Phase	Status	Notes
Pre-Flight	✅ COMPLETE	Context gathered; prior review imported
Gate	❌ FAILED	Missing baseline snapshot (same as prior review)
Fix	⏩ SKIPPED	Gate did not pass; code analysis performed manually
Report	✅ COMPLETE	REQUEST CHANGES for baseline snapshot

PR Quality Assessment

Aspect	Assessment
Fix correctness	✅ Logically correct
Fix scope	✅ Minimal, iOS-only
Code quality	✅ Well-commented, follows conventions
Test structure	✅ Correct (orientation mismatch fixed in prior commit)
Test baseline	❌ Missing — CI will fail every run
Title accuracy	✅ Accurate

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📋 Expand PR Finalization Review

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Title: ✅ Good

Current: [iOS] Fix ScrollView with RTL FlowDirection and Horizontal Orientation scrolls in the wrong direction

Description: ✅ Good

Description needs updates. See details below.

✨ Suggested PR Description

[!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

When a ScrollView has FlowDirection=RightToLeft and its Orientation is changed at runtime, the RTL content-offset adjustment in MauiScrollView.CrossPlatformArrange is not re-triggered.

The RTL adjustment logic (which repositions content and sets ContentOffset for right-to-left scrolling) only runs when _previousEffectiveUserInterfaceLayoutDirection != EffectiveUserInterfaceLayoutDirection. On initial load this fires once (previous is null, current is RightToLeft), then _previousEffectiveUserInterfaceLayoutDirection is set to RightToLeft. On subsequent layout passes (including those triggered by an orientation change), both values are RightToLeft, so the condition is false and the RTL adjustment is skipped — leaving the content offset wrong for the new orientation.

Description of Change

MauiScrollView.cs (iOS platform layer)

Added internal void OnOrientationChanged(). When the current layout direction is RightToLeft, this method resets _previousEffectiveUserInterfaceLayoutDirection to null, then calls SetNeedsLayout() and LayoutIfNeeded(). This tricks the RTL adjustment logic into believing the layout direction "changed" on the next arrange pass, causing it to recalculate the horizontal content offset for the new orientation.

ScrollViewHandler.iOS.cs

In MapOrientation, after updating the enabled state and before calling InvalidateMeasure, the handler now calls mauiScrollView.OnOrientationChanged() when the platform view is a MauiScrollView and IsLoaded() is true. The IsLoaded() guard prevents interference during the initial load path, where the RTL adjustment already works correctly.

Test files

Added Issue32271.cs in TestCases.HostApp/Issues/ and TestCases.Shared.Tests/Tests/Issues/. The host app page sets up a ScrollView with FlowDirection=RightToLeft, binds Orientation to a viewmodel, and provides a "Toggle Orientation" button and a "Scroll" button. The NUnit test taps "Toggle Orientation" (Vertical → Horizontal), taps "Scroll", and verifies via screenshot.

Key Technical Details

Relevant field: _previousEffectiveUserInterfaceLayoutDirection (UIUserInterfaceLayoutDirection?) in MauiScrollView

• Tracks last-seen layout direction to gate the RTL one-time adjustment
• Setting it to null re-arms the RTL adjustment for the next layout pass

Affected scenario: RTL + runtime Orientation change only. Initial load (Vertical or Horizontal with RTL) is unaffected because the direction tracking fires normally on first arrange.

IsLoaded() guard: Prevents calling OnOrientationChanged() during initial mapper setup, where _previousEffectiveUserInterfaceLayoutDirection is already null and no reset is needed.

Issues Fixed

Fixes #32271

Platforms Tested

• Android
• Windows
• iOS
• Mac

Code Review: ✅ Passed

Code Review — PR #32529

🟡 Suggestions

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1. LayoutIfNeeded() in OnOrientationChanged() may be redundant

File: src/Core/src/Platform/iOS/MauiScrollView.cs

internal void OnOrientationChanged()
{
    if (_previousEffectiveUserInterfaceLayoutDirection == UIUserInterfaceLayoutDirection.RightToLeft)
    {
        _previousEffectiveUserInterfaceLayoutDirection = null;
        SetNeedsLayout();
        LayoutIfNeeded();  // <-- concern
    }
}

LayoutIfNeeded() forces a synchronous layout pass. At this point the orientation hasn't actually been applied to the cross-platform layout yet — InvalidateMeasure (the call that follows in MapOrientation) is what drives the full re-measure+arrange cycle. If the scroll view's frame hasn't changed, LayoutSubviews will see frameChanged = false and skip CrossPlatformArrange, meaning the _previousEffectiveUserInterfaceLayoutDirection = null reset will persist until the InvalidateMeasure-triggered pass anyway.

The LayoutIfNeeded() call is not harmful but its value is unclear. It could force an intermediate layout pass with stale dimensions. At minimum, a comment explaining why the immediate synchronous layout is necessary (vs. letting InvalidateMeasure handle it) would make this clearer.

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2. VerifyScreenshot() without a stability wait after scroll

File: src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs

public void VerifyScrollViewDirection()
{
    App.WaitForElement("ToggleOrientationButton");
    App.Tap("ToggleOrientationButton");
    App.Tap("ScrollToEndButton");
    VerifyScreenshot();  // called immediately after tap
}

The "Scroll" button triggers ScrollToAsync(..., animated: true). The animated scroll may not complete before VerifyScreenshot() is called, making the screenshot non-deterministic. Consider using VerifyScreenshot(retryTimeout: TimeSpan.FromSeconds(2)) to allow the animation to settle:

VerifyScreenshot(retryTimeout: TimeSpan.FromSeconds(2));

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3. Screenshot-only assertion does not verify scroll direction correctness

File: src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs

The test verifies visual appearance via screenshot but does not verify the actual scroll direction programmatically. If the scroll position is wrong (the original bug), the screenshot would differ from the baseline — but only after a baseline has been established with the fix applied. This is reasonable for a regression test, though a GetRect()-based position check would be more robust.

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4. Missing newline at end of test file

File: src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32271.cs

The diff shows \ No newline at end of file. All source files should end with a newline.

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5. Nullable annotation gap in test viewmodel

File: src/Controls/tests/TestCases.HostApp/Issues/Issue32271.cs

View _content;  // not nullable, but initialized via constructor path

The field _content is a reference type declared without ?. The compiler may emit a nullable warning since it's not initialized in the field declaration. It's initialized via the Content setter in the constructor (Content = new Label {...}), but the declaration should use View? _content; to match the nullable intent:

View? _content;

Similarly, the PropertyChanged event:

public event PropertyChangedEventHandler PropertyChanged;
// should be:
public event PropertyChangedEventHandler? PropertyChanged;

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6. Dead code: ContentText property in test viewmodel

File: src/Controls/tests/TestCases.HostApp/Issues/Issue32271.cs

public string ContentText
{
    get => _contentText;
    set { ... Content = new Label { Text = _contentText }; ... }
}

ContentText (and the backing field _contentText) is never bound or used in the test page. It appears to be carry-over from the issue reporter's original reproduction. It creates a dead Label on set and can be removed.

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✅ Looks Good

• IsLoaded() guard in MapOrientation correctly prevents the orientation-change path from firing during initial mapper setup — good defensive coding.
• OnOrientationChanged() scope — correctly scoped to internal, not public API.
• RTL-only guard — if (_previousEffectiveUserInterfaceLayoutDirection == UIUserInterfaceLayoutDirection.RightToLeft) correctly limits the reset to RTL views, avoiding interference with LTR scrollviews.
• Test page structure — uses viewmodel + binding for orientation, matching real-world usage patterns that trigger the bug.
• [Category(UITestCategories.ScrollView)] — correct category for the test.
• platformView is MauiScrollView type check — safe cast before calling the new method.

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[kubaflo]

Could you please add snapshot?

[sheiksyedm]

/azp run maui-pr-uitests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[devanathan-vaithiyanathan]

Could you please check the ai's suggestions?

@kubaflo , Based on AI suggestion, I have modified the fix

[kubaflo]

/review -b feature/enhanced-reviewer