Fix Shell RTL layout and content propagation on iOS/MacCatalyst

[Copilot]

Fixes dotnet#32419

Shell with FlowDirection="RightToLeft" on iOS/MacCatalyst had two issues:

1. With FlyoutBehavior="Locked", flyout and content positioning ignored RTL (both appeared in LTR layout)
2. Content pages inside Shell remained LTR regardless of Shell's FlowDirection

Changes

SlideFlyoutTransition.cs - Fixed flyout/content positioning for RTL

Refactored LayoutViews() to check SemanticContentAttribute and position views accordingly:

bool isRtl = shell.SemanticContentAttribute == UISemanticContentAttribute.ForceRightToLeft;

if (behavior == FlyoutBehavior.Locked)
{
    if (isRtl)
    {
        // RTL: flyout right, content left
        shell.Frame = new CGRect(bounds.X, bounds.Y, bounds.Width - flyoutWidth, flyoutHeight);
        flyout.Frame = new CGRect(bounds.Width - flyoutWidth, 0, flyoutWidth, flyoutHeight);
    }
    else
    {
        // LTR: flyout left, content right (original behavior)
        shell.Frame = new CGRect(bounds.X + flyoutWidth, bounds.Y, bounds.Width - flyoutWidth, flyoutHeight);
        flyout.Frame = new CGRect(0, 0, flyoutWidth, flyoutHeight);
    }
}

ShellSectionRootRenderer.cs - Propagate RTL to content pages

Enhanced UpdateFlowDirection() to update current content page's platform view:

void UpdateFlowDirection()
{
    if (_shellContext?.Shell?.CurrentItem?.CurrentItem == ShellSection)
    {
        this.View.UpdateFlowDirection(_shellContext.Shell);
        
        // Propagate to content page
        if (_currentContent != null)
        {
            var page = ((IShellContentController)_currentContent).GetOrCreateContent();
            if (page?.Handler?.PlatformView is UIView pageView)
            {
                pageView.UpdateFlowDirection(page);
            }
        }
    }
}

Also added UpdateFlowDirection() call when current content changes to ensure new pages inherit correct direction.

Tests

Added UI tests (Issue32419.xaml, Issue32419Page.xaml, Issue32419.cs) validating:

• Locked flyout positions correctly in RTL (flyout right, content left)
• Content page elements align right in RTL mode
• Screenshot verification for visual correctness

Platforms

• iOS ✓
• MacCatalyst ✓ (shares iOS implementation)

Original prompt

fix dotnet#32419

Custom agent used: issue-resolver
Specialized agent for investigating and resolving community-reported .NET MAUI issues through hands-on testing and implementation

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.