Avalonia/Perspex.Controls/Popup.cs

// -----------------------------------------------------------------------
// <copyright file="Popup.cs" company="Steven Kirk">
// Copyright 2014 MIT Licence. See licence.md for more information.
// </copyright>
// -----------------------------------------------------------------------

namespace Perspex.Controls
{
    using System;
    using Perspex.Interactivity;
    using Perspex.Collections;
    using Perspex.Rendering;
    using Perspex.VisualTree;

    public class Popup : Control, ILogical, IVisualTreeHost
    {
        public static readonly PerspexProperty<Control> ChildProperty =
            PerspexProperty.Register<Popup, Control>("Child");

        public static readonly PerspexProperty<bool> IsOpenProperty =
            PerspexProperty.Register<Popup, bool>("IsOpen");

        public static readonly PerspexProperty<PlacementMode> PlacementModeProperty =
            PerspexProperty.Register<Popup, PlacementMode>("PlacementMode", defaultValue: PlacementMode.Bottom);

        public static readonly PerspexProperty<Control> PlacementTargetProperty =
            PerspexProperty.Register<Popup, Control>("PlacementTarget");

        public static readonly PerspexProperty<bool> StaysOpenProperty =
            PerspexProperty.Register<Popup, bool>("StaysOpen", true);

        private PopupRoot popupRoot;

        private TopLevel topLevel;

        private PerspexSingleItemList<ILogical> logicalChild = new PerspexSingleItemList<ILogical>();

        static Popup()
        {
            IsOpenProperty.Changed.Subscribe(IsOpenChanged);
        }

        public Popup()
        {
            this.GetObservableWithHistory(ChildProperty).Subscribe(ChildChanged);
        }

        public event EventHandler Closed;

        public event EventHandler Opened;

        public event EventHandler PopupRootCreated;

        public Control Child
        {
            get { return this.GetValue(ChildProperty); }
            set { this.SetValue(ChildProperty, value); }
        }

        public bool IsOpen
        {
            get { return this.GetValue(IsOpenProperty); }
            set { this.SetValue(IsOpenProperty, value); }
        }

        public PlacementMode PlacementMode
        {
            get { return this.GetValue(PlacementModeProperty); }
            set { this.SetValue(PlacementModeProperty, value); }
        }

        public Control PlacementTarget
        {
            get { return this.GetValue(PlacementTargetProperty); }
            set { this.SetValue(PlacementTargetProperty, value); }
        }

        public PopupRoot PopupRoot
        {
            get { return this.popupRoot; }
        }

        public bool StaysOpen
        {
            get { return this.GetValue(StaysOpenProperty); }
            set { this.SetValue(StaysOpenProperty, value); }
        }

        IPerspexReadOnlyList<ILogical> ILogical.LogicalChildren
        {
            get { return this.logicalChild; }
        }

        IVisual IVisualTreeHost.Root
        {
            get { return this.popupRoot; }
        }

        public void Open()
        {
            if (this.popupRoot == null)
            {
                this.popupRoot = new PopupRoot()
                {
                    Parent = this,
                    [~PopupRoot.ContentProperty] = this[~ChildProperty],
                    [~PopupRoot.WidthProperty] = this[~WidthProperty],
                    [~PopupRoot.HeightProperty] = this[~HeightProperty],
                    [~PopupRoot.MinWidthProperty] = this[~MinWidthProperty],
                    [~PopupRoot.MaxWidthProperty] = this[~MaxWidthProperty],
                    [~PopupRoot.MinHeightProperty] = this[~MinHeightProperty],
                    [~PopupRoot.MaxHeightProperty] = this[~MaxHeightProperty],
                };
            }

            this.popupRoot.SetPosition(this.GetPosition());
            this.topLevel.Deactivated += this.MaybeClose;
            this.popupRoot.AddHandler(PopupRoot.PointerPressedEvent, this.MaybeClose, RoutingStrategies.Bubble, true);
            this.topLevel.AddHandler(TopLevel.PointerPressedEvent, this.MaybeClose, RoutingStrategies.Tunnel);

            this.PopupRootCreated?.Invoke(this, EventArgs.Empty);

            this.popupRoot.Show();
            this.IsOpen = true;
            this.Opened?.Invoke(this, EventArgs.Empty);
        }

        public void Close()
        {
            if (this.popupRoot != null)
            {
                this.popupRoot.PointerPressed -= this.MaybeClose;
                this.topLevel.RemoveHandler(TopLevel.PointerPressedEvent, this.MaybeClose);
                this.topLevel.Deactivated -= this.MaybeClose;
                this.popupRoot.Hide();
            }

            this.IsOpen = false;
            this.Closed?.Invoke(this, EventArgs.Empty);
        }

        protected override Size MeasureCore(Size availableSize)
        {
            return new Size();
        }

        protected override void OnAttachedToVisualTree(IRenderRoot root)
        {
            base.OnAttachedToVisualTree(root);
            this.topLevel = root as TopLevel;
        }

        protected override void OnDetachedFromVisualTree(IRenderRoot oldRoot)
        {
            base.OnDetachedFromVisualTree(oldRoot);
            this.topLevel = null;
        }

        private static void IsOpenChanged(PerspexPropertyChangedEventArgs e)
        {
            Popup popup = e.Sender as Popup;

            if (popup != null)
            {
                if ((bool)e.NewValue)
                {
                    popup.Open();
                }
                else
                {
                    popup.Close();
                }
            }
        }

        private void ChildChanged(Tuple<Control, Control> values)
        {
            if (values.Item1 != null)
            {
                values.Item1.Parent = null;
            }

            if (values.Item2 != null)
            {
                values.Item2.Parent = this;
            }

            this.logicalChild.SingleItem = values.Item2;
        }

        private Point GetPosition()
        {
            var target = this.PlacementTarget ?? this.GetVisualParent<Control>();
            Point point;

            switch (this.PlacementMode)
            {
                case PlacementMode.Bottom:
                    point = target.Bounds.BottomLeft;
                    break;
                case PlacementMode.Right:
                    point = target.Bounds.TopRight;
                    break;
                default:
                    throw new InvalidOperationException("Invalid value for Popup.PlacementMode");
            }

            if (target != null)
            {
                return target.PointToScreen(point);
            }
            else
            {
                return new Point();
            }
        }

        private void MaybeClose(object sender, EventArgs e)
        {
            if (!this.StaysOpen)
            {
                var routed = e as RoutedEventArgs;

                if (routed != null)
                {
                    routed.Handled = true;
                }

                this.Close();
            }
        }
    }
}