Unified iOS FlyoutViewHandler

[PureWeen]

Unified iOS FlyoutViewHandler

Target: .NET 10

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Goal

Implement FlyoutViewHandler for iOS, replacing the legacy PhoneFlyoutPageRenderer. Learn from both the existing renderer implementation and Shell's flyout handling to build a unified handler that both FlyoutPage and Shell can use.

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Background

• WinUI already has a shared flyout handling approach
• iOS currently uses PhoneFlyoutPageRenderer (in Microsoft.Maui.Controls.Handlers.Compatibility)
• There's also TabletFlyoutPageRenderer for iPad split view scenarios
• Shell has its own flyout implementation that duplicates much of the same logic

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Rollout Strategy

1. Implement FlyoutViewHandler for .NET 10

2. Gate behind AppContext switch - Wire FlyoutPage to use the new handler when the switch is enabled

3. Switch disabled by default initially - Allows testing and validation without affecting existing apps

4. Enable for FlyoutPage and Shell - Once validated, flip the switch to make it the default path

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Guidelines

1. Implement FlyoutViewHandler for iOS - Handle both phone and tablet scenarios

2. Learn from PhoneFlyoutPageRenderer - Extract patterns for flyout presentation, gestures, FlyoutLayoutBehavior handling

3. Learn from Shell flyout handling - Incorporate patterns that work well for Shell's flyout

4. FlyoutPage and Shell both use it - Same handler, different consumers

5. Keep handler internal initially - Flexibility to iterate without public API commitment

6. Align with WinUI patterns - Use WinUI's unified approach as the reference model

7. Handle FlyoutLayoutBehavior modes - Default, Popover, Split, SplitOnLandscape, SplitOnPortrait

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Success Criteria

• FlyoutViewHandler works on iOS (phone and tablet)
• FlyoutPage uses the new handler (when switch enabled)
• Shell can use the same handler for flyout (when switch enabled)
• All existing FlyoutPage tests pass with switch enabled
• All existing Shell flyout tests pass with switch enabled