FlyoutPage.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Microsoft.Maui.Controls.Internals;
using Microsoft.Maui.Devices;
using Microsoft.Maui.Graphics;

namespace Microsoft.Maui.Controls
{
	/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="Type[@FullName='Microsoft.Maui.Controls.FlyoutPage']/Docs" />
	[ContentProperty(nameof(Detail))]
	public partial class FlyoutPage : Page, IFlyoutPageController, IElementConfiguration<FlyoutPage>
	{
		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='IsGestureEnabledProperty']/Docs" />
		public static readonly BindableProperty IsGestureEnabledProperty = BindableProperty.Create(nameof(IsGestureEnabled), typeof(bool), typeof(FlyoutPage), true);

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='IsPresentedProperty']/Docs" />
		public static readonly BindableProperty IsPresentedProperty = BindableProperty.Create(nameof(IsPresented), typeof(bool), typeof(FlyoutPage), default(bool),
			propertyChanged: OnIsPresentedPropertyChanged, propertyChanging: OnIsPresentedPropertyChanging, defaultValueCreator: GetDefaultValue);

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='FlyoutLayoutBehaviorProperty']/Docs" />
		public static readonly BindableProperty FlyoutLayoutBehaviorProperty = BindableProperty.Create(nameof(FlyoutLayoutBehavior), typeof(FlyoutLayoutBehavior), typeof(FlyoutPage), default(FlyoutLayoutBehavior),
			propertyChanged: OnFlyoutLayoutBehaviorPropertyChanged);

		Page _detail;

		Rect _detailBounds;

		Page _flyout;

		Rect _flyoutBounds;

		IFlyoutPageController FlyoutPageController => this;

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='Detail']/Docs" />
		public Page Detail
		{
			get { return _detail; }
			set
			{
				if (_detail != null && value == null)
					throw new ArgumentNullException("value", "Detail cannot be set to null once a value is set.");

				if (_detail == value)
					return;

				if (value.RealParent != null)
					throw new InvalidOperationException("Detail must not already have a parent.");

				var previousDetail = _detail;
				// TODO MAUI refine this to fire earlier
				_detail?.SendNavigatingFrom(new NavigatingFromEventArgs());

				OnPropertyChanging();
				if (_detail != null)
					InternalChildren.Remove(_detail);
				_detail = value;
				InternalChildren.Add(_detail);
				OnPropertyChanged();

				if (this.HasAppeared)
				{
					previousDetail?.SendDisappearing();
					_detail?.SendAppearing();
				}

				previousDetail?.SendNavigatedFrom(new NavigatedFromEventArgs(_detail));
				_detail?.SendNavigatedTo(new NavigatedToEventArgs(previousDetail));
			}
		}

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='IsGestureEnabled']/Docs" />
		public bool IsGestureEnabled
		{
			get { return (bool)GetValue(IsGestureEnabledProperty); }
			set { SetValue(IsGestureEnabledProperty, value); }
		}

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='IsPresented']/Docs" />
		public bool IsPresented
		{
			get { return (bool)GetValue(IsPresentedProperty); }
			set { SetValue(IsPresentedProperty, value); }
		}

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='Flyout']/Docs" />
		public Page Flyout
		{
			get { return _flyout; }
			set
			{
				if (_flyout != null && value == null)
					throw new ArgumentNullException("value", "Flyout cannot be set to null once a value is set");

				if (string.IsNullOrEmpty(value.Title))
					throw new InvalidOperationException("Title property must be set on Flyout page");

				if (_flyout == value)
					return;

				if (value.RealParent != null)
					throw new InvalidOperationException("Flyout must not already have a parent.");

				// TODO MAUI refine this to fire earlier
				var previousFlyout = _flyout;
				// TODO MAUI refine this to fire earlier
				_flyout?.SendNavigatingFrom(new NavigatingFromEventArgs());

				OnPropertyChanging();
				if (_flyout != null)
					InternalChildren.Remove(_flyout);
				_flyout = value;
				InternalChildren.Add(_flyout);
				OnPropertyChanged();

				if (this.HasAppeared)
				{
					previousFlyout?.SendDisappearing();
					_flyout?.SendAppearing();
				}

				previousFlyout?.SendNavigatedFrom(new NavigatedFromEventArgs(_flyout));
				_flyout?.SendNavigatedTo(new NavigatedToEventArgs(previousFlyout));
			}
		}

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='FlyoutLayoutBehavior']/Docs" />
		public FlyoutLayoutBehavior FlyoutLayoutBehavior
		{
			get { return (FlyoutLayoutBehavior)GetValue(FlyoutLayoutBehaviorProperty); }
			set { SetValue(FlyoutLayoutBehaviorProperty, value); }
		}

		bool IFlyoutPageController.CanChangeIsPresented { get; set; } = true;

		Rect IFlyoutPageController.DetailBounds
		{
			get { return _detailBounds; }
			set
			{
				_detailBounds = value;
				if (_detail == null)
					throw new InvalidOperationException("Detail must be set before using a FlyoutPage");
				_detail.Layout(value);
			}
		}

		Rect IFlyoutPageController.FlyoutBounds
		{
			get { return _flyoutBounds; }
			set
			{
				_flyoutBounds = value;
				if (_flyout == null)
					throw new InvalidOperationException("Flyout must be set before using a FlyoutPage");
				_flyout.Layout(value);
			}
		}

		bool IFlyoutPageController.ShouldShowSplitMode
		{
			get
			{
				if (DeviceInfo.Idiom == DeviceIdiom.Phone)
					return false;

				FlyoutLayoutBehavior behavior = FlyoutLayoutBehavior;
				var orientation = Window.GetOrientation();

				bool isSplitOnLandscape = (behavior == FlyoutLayoutBehavior.SplitOnLandscape || behavior == FlyoutLayoutBehavior.Default) && orientation.IsLandscape();
				bool isSplitOnPortrait = behavior == FlyoutLayoutBehavior.SplitOnPortrait && orientation.IsPortrait();
				return behavior == FlyoutLayoutBehavior.Split || isSplitOnLandscape || isSplitOnPortrait;
			}
		}

		public event EventHandler IsPresentedChanged;

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='ShouldShowToolbarButton']/Docs" />
		public virtual bool ShouldShowToolbarButton()
		{
			if (DeviceInfo.Idiom == DeviceIdiom.Phone)
				return true;

			FlyoutLayoutBehavior behavior = FlyoutLayoutBehavior;
			var orientation = DeviceDisplay.MainDisplayInfo.Orientation;

			bool isSplitOnLandscape = (behavior == FlyoutLayoutBehavior.SplitOnLandscape || behavior == FlyoutLayoutBehavior.Default) && orientation.IsLandscape();
			bool isSplitOnPortrait = behavior == FlyoutLayoutBehavior.SplitOnPortrait && orientation.IsPortrait();
			return behavior != FlyoutLayoutBehavior.Split && !isSplitOnLandscape && !isSplitOnPortrait;
		}

		protected override void LayoutChildren(double x, double y, double width, double height)
		{
			if (Flyout == null || Detail == null)
				throw new InvalidOperationException("Flyout and Detail must be set before using a FlyoutPage");

#if !ANDROID
			_flyout.Layout(_flyoutBounds);
			_detail.Layout(_detailBounds);
#endif
		}

		protected override void OnAppearing()
		{
			Flyout?.SendAppearing();
			Detail?.SendAppearing();

			FlyoutPageController.CanChangeIsPresented = true;
			UpdateFlyoutLayoutBehavior(this);
			base.OnAppearing();
		}

		protected override bool OnBackButtonPressed()
		{
			if (IsPresented)
			{
				if (Flyout.SendBackButtonPressed())
					return true;
			}

			EventHandler<BackButtonPressedEventArgs> handler = BackButtonPressed;
			if (handler != null)
			{
				var args = new BackButtonPressedEventArgs();
				handler(this, args);
				if (args.Handled)
					return true;
			}

			if (Detail.SendBackButtonPressed())
			{
				return true;
			}

			return base.OnBackButtonPressed();
		}

		protected override void OnParentSet()
		{
			if (RealParent != null && (Flyout == null || Detail == null))
				throw new InvalidOperationException("Flyout and Detail must be set before adding FlyoutPage to a container");
			base.OnParentSet();
		}

		[EditorBrowsable(EditorBrowsableState.Never)]
		public event EventHandler<BackButtonPressedEventArgs> BackButtonPressed;

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='UpdateFlyoutLayoutBehavior']/Docs" />
		[EditorBrowsable(EditorBrowsableState.Never)]
		public void UpdateFlyoutLayoutBehavior()
		{
			UpdateFlyoutLayoutBehavior(this);
		}

		internal static void UpdateFlyoutLayoutBehavior(FlyoutPage page)
		{
			if (page is IFlyoutPageController fpc && fpc.ShouldShowSplitMode)
			{
				page.SetValueCore(IsPresentedProperty, true);
				if (page.FlyoutLayoutBehavior != FlyoutLayoutBehavior.Default)
					fpc.CanChangeIsPresented = false;
			}
		}

		static void OnIsPresentedPropertyChanged(BindableObject sender, object oldValue, object newValue)
			=> ((FlyoutPage)sender).IsPresentedChanged?.Invoke(sender, EventArgs.Empty);

		static void OnIsPresentedPropertyChanging(BindableObject sender, object oldValue, object newValue)
		{
			if (sender is Maui.IElement element && element.IsShimmed())
			{
				if (sender is FlyoutPage fp && fp is IFlyoutPageController fpc && !fpc.CanChangeIsPresented)
					throw new InvalidOperationException(string.Format("Can't change IsPresented when setting {0}", fp.FlyoutLayoutBehavior));
			}
			else
			{
				if ((!(bool)newValue) && sender is IFlyoutPageController fpc && fpc.ShouldShowSplitMode && sender is FlyoutPage fp)
				{
					throw new InvalidOperationException(string.Format("Can't change IsPresented when setting {0}", fp.FlyoutLayoutBehavior));
				}
			}
		}

		static void OnFlyoutLayoutBehaviorPropertyChanged(BindableObject sender, object oldValue, object newValue)
		{
			var page = (FlyoutPage)sender;
			UpdateFlyoutLayoutBehavior(page);
		}

		static object GetDefaultValue(BindableObject bindable)
		{
			return DeviceInfo.Platform == DevicePlatform.macOS;
		}

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='.ctor']/Docs" />
		public FlyoutPage()
		{
			_platformConfigurationRegistry = new Lazy<PlatformConfigurationRegistry<FlyoutPage>>(() => new PlatformConfigurationRegistry<FlyoutPage>(this));

			this.Loaded += OnLoaded;
			this.Unloaded += OnUnloaded;
		}

		readonly Lazy<PlatformConfigurationRegistry<FlyoutPage>> _platformConfigurationRegistry;

		/// <include file="../../docs/Microsoft.Maui.Controls/FlyoutPage.xml" path="//Member[@MemberName='On']/Docs" />
		public new IPlatformElementConfiguration<T, FlyoutPage> On<T>() where T : IConfigPlatform
		{
			return _platformConfigurationRegistry.Value.On<T>();
		}

		void OnUnloaded(object sender, EventArgs e)
		{
			DeviceDisplay.MainDisplayInfoChanged -= OnMainDisplayInfoChanged;
		}

		void OnLoaded(object sender, EventArgs e)
		{
			DeviceDisplay.MainDisplayInfoChanged += OnMainDisplayInfoChanged;
			Handler?.UpdateValue(nameof(FlyoutBehavior));
		}

		void OnMainDisplayInfoChanged(object sender, DisplayInfoChangedEventArgs e)
		{
			Handler?.UpdateValue(nameof(FlyoutBehavior));
		}
	}
}