maui-linux/Xamarin.Forms.Core/TemplatedView.cs

using System;
using System.Collections.Generic;

namespace Xamarin.Forms
{
	public class TemplatedView : Layout, IControlTemplated
	{
		public static readonly BindableProperty ControlTemplateProperty = BindableProperty.Create(nameof(ControlTemplate), typeof(ControlTemplate), typeof(TemplatedView), null,
			propertyChanged: TemplateUtilities.OnControlTemplateChanged);

		public ControlTemplate ControlTemplate
		{
			get { return (ControlTemplate)GetValue(ControlTemplateProperty); }
			set { SetValue(ControlTemplateProperty, value); }
		}

		IList<Element> IControlTemplated.InternalChildren => InternalChildren;

		protected override void LayoutChildren(double x, double y, double width, double height)
		{
			for (var i = 0; i < LogicalChildrenInternal.Count; i++)
			{
				Element element = LogicalChildrenInternal[i];
				var child = element as View;
				if (child != null)
					LayoutChildIntoBoundingRegion(child, new Rectangle(x, y, width, height));
			}
		}

		[Obsolete("OnSizeRequest is obsolete as of version 2.2.0. Please use OnMeasure instead.")]
		protected override SizeRequest OnSizeRequest(double widthConstraint, double heightConstraint)
		{
			double widthRequest = WidthRequest;
			double heightRequest = HeightRequest;
			var childRequest = new SizeRequest();

			if ((widthRequest == -1 || heightRequest == -1) && InternalChildren.Count > 0)
			{
				childRequest = ((View)InternalChildren[0]).Measure(widthConstraint, heightConstraint, MeasureFlags.IncludeMargins);
			}

			return new SizeRequest
			{
				Request = new Size { Width = widthRequest != -1 ? widthRequest : childRequest.Request.Width, Height = heightRequest != -1 ? heightRequest : childRequest.Request.Height },
				Minimum = childRequest.Minimum
			};
		}

		internal override void ComputeConstraintForView(View view)
		{
			bool isFixedHorizontally = (Constraint & LayoutConstraint.HorizontallyFixed) != 0;
			bool isFixedVertically = (Constraint & LayoutConstraint.VerticallyFixed) != 0;

			var result = LayoutConstraint.None;
			if (isFixedVertically && view.VerticalOptions.Alignment == LayoutAlignment.Fill)
				result |= LayoutConstraint.VerticallyFixed;
			if (isFixedHorizontally && view.HorizontalOptions.Alignment == LayoutAlignment.Fill)
				result |= LayoutConstraint.HorizontallyFixed;
			view.ComputedConstraint = result;
		}

		internal override void SetChildInheritedBindingContext(Element child, object context)
		{
			if (ControlTemplate == null)
				base.SetChildInheritedBindingContext(child, context);
		}

		void IControlTemplated.OnControlTemplateChanged(ControlTemplate oldValue, ControlTemplate newValue)
		{
			OnControlTemplateChanged(oldValue, newValue);
		}

		internal virtual void OnControlTemplateChanged(ControlTemplate oldValue, ControlTemplate newValue)
		{
		}
	}
}