Avalonia/src/Avalonia.Controls/Primitives/PopupRoot.cs

// Copyright (c) The Avalonia Project. All rights reserved.
// Licensed under the MIT license. See licence.md file in the project root for full license information.

using System;
using System.Collections.Generic;
using System.Reactive.Disposables;
using Avalonia.Controls.Primitives.PopupPositioning;
using Avalonia.Interactivity;
using Avalonia.Media;
using Avalonia.Platform;
using Avalonia.Styling;
using Avalonia.VisualTree;
using JetBrains.Annotations;

namespace Avalonia.Controls.Primitives
{
    /// <summary>
    /// The root window of a <see cref="Popup"/>.
    /// </summary>
    public sealed class PopupRoot : WindowBase, IInteractive, IHostedVisualTreeRoot, IDisposable, IStyleHost, IPopupHost
    {
        private readonly TopLevel _parent;
        private PopupPositionerParameters _positionerParameters;

        /// <summary>
        /// Initializes static members of the <see cref="PopupRoot"/> class.
        /// </summary>
        static PopupRoot()
        {
            BackgroundProperty.OverrideDefaultValue(typeof(PopupRoot), Brushes.White);
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="PopupRoot"/> class.
        /// </summary>
        public PopupRoot(TopLevel parent, IPopupImpl impl)
            : this(parent, impl,null)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="PopupRoot"/> class.
        /// </summary>
        /// <param name="dependencyResolver">
        /// The dependency resolver to use. If null the default dependency resolver will be used.
        /// </param>
        public PopupRoot(TopLevel parent, IPopupImpl impl, IAvaloniaDependencyResolver dependencyResolver)
            : base(impl, dependencyResolver)
        {
            _parent = parent;
        }

        /// <summary>
        /// Gets the platform-specific window implementation.
        /// </summary>
        [CanBeNull]
        public new IPopupImpl PlatformImpl => (IPopupImpl)base.PlatformImpl;

        /// <summary>
        /// Gets the parent control in the event route.
        /// </summary>
        /// <remarks>
        /// Popup events are passed to their parent window. This facilitates this.
        /// </remarks>
        IInteractive IInteractive.InteractiveParent => Parent;

        /// <summary>
        /// Gets the control that is hosting the popup root.
        /// </summary>
        IVisual IHostedVisualTreeRoot.Host => Parent;

        /// <summary>
        /// Gets the styling parent of the popup root.
        /// </summary>
        IStyleHost IStyleHost.StylingParent => Parent;

        /// <inheritdoc/>
        public void Dispose() => PlatformImpl?.Dispose();

        private void UpdatePosition()
        {
            PlatformImpl?.PopupPositioner.Update(_positionerParameters);
        }

        public void ConfigurePosition(IVisual target, PlacementMode placement, Point offset,
            PopupPositioningEdge anchor = PopupPositioningEdge.None,
            PopupPositioningEdge gravity = PopupPositioningEdge.None)
        {
            _positionerParameters.ConfigurePosition(_parent, target,
                placement, offset, anchor, gravity);

            if (_positionerParameters.Size != default)
                UpdatePosition();
        }

        public void SetChild(IControl control) => Content = control;

        IVisual IPopupHost.HostedVisualTreeRoot => this;
        
        public IDisposable BindConstraints(AvaloniaObject popup, StyledProperty<double> widthProperty, StyledProperty<double> minWidthProperty,
            StyledProperty<double> maxWidthProperty, StyledProperty<double> heightProperty, StyledProperty<double> minHeightProperty,
            StyledProperty<double> maxHeightProperty, StyledProperty<bool> topmostProperty)
        {
            var bindings = new List<IDisposable>();

            void Bind(AvaloniaProperty what, AvaloniaProperty to) => bindings.Add(this.Bind(what, popup[~to]));
            Bind(WidthProperty, widthProperty);
            Bind(MinWidthProperty, minWidthProperty);
            Bind(MaxWidthProperty, maxWidthProperty);
            Bind(HeightProperty, heightProperty);
            Bind(MinHeightProperty, minHeightProperty);
            Bind(MaxHeightProperty, maxHeightProperty);
            Bind(TopmostProperty, topmostProperty);
            return Disposable.Create(() =>
            {
                foreach (var x in bindings)
                    x.Dispose();
            });
        }

        /// <summary>
        /// Carries out the arrange pass of the window.
        /// </summary>
        /// <param name="finalSize">The final window size.</param>
        /// <returns>The <paramref name="finalSize"/> parameter unchanged.</returns>
        protected override Size ArrangeOverride(Size finalSize)
        {
            using (BeginAutoSizing())
            {
                _positionerParameters.Size = finalSize;
                UpdatePosition();
            }

            return base.ArrangeOverride(PlatformImpl?.ClientSize ?? default(Size));
        }
    }
}