/// <summary>
        /// Renders the specified visual.
        /// </summary>
        /// <param name="visual">The visual to render.</param>
        /// 
        /// <param name="context">The drawing context.</param>
        public static void Render(this DrawingContext context, IVisual visual)
        {
            var opacity = visual.Opacity;
            if (visual.IsVisible && opacity > 0)
            {
                var m = Matrix.CreateTranslation(visual.Bounds.Position);

                var renderTransform = Matrix.Identity;

                if (visual.RenderTransform != null)
                {
                    var origin = visual.TransformOrigin.ToPixels(new Size(visual.Bounds.Width, visual.Bounds.Height));
                    var offset = Matrix.CreateTranslation(origin);
                    renderTransform = (-offset)*visual.RenderTransform.Value*(offset);
                }
                m = renderTransform*m;

                using (context.PushPostTransform(m))
                using (context.PushOpacity(opacity))
                using (visual.ClipToBounds ? context.PushClip(new Rect(visual.Bounds.Size)) : default(DrawingContext.PushedState))
                using (context.PushTransformContainer())
                {
                    visual.Render(context);
                    foreach (var child in visual.VisualChildren.OrderBy(x => x.ZIndex))
                    {
                        context.Render(child);
                    }
                }
            }
        }

        /// <summary>
        /// Translates a point relative to this visual to coordinates that are relative to the specified visual.
        /// The visual and relativeTo should be descendants of the same root window
        /// </summary>
        /// <param name="visual">The visual.</param>
        /// <param name="point">The point value, as relative to this visual.</param>
        /// <param name="relativeTo">The visual to translate the given point into.</param>
        /// <returns>A point value, now relative to the target visual rather than this source element.</returns>
        public static Point TranslatePoint(this IVisual visual, Point point, IVisual relativeTo)
        {
            var pos = GetRootAndPosition(visual);
            var relToPos = GetRootAndPosition(relativeTo);

            return point - (relToPos.Item2 - pos.Item2);
        }

 public static AdornerLayer GetAdornerLayer(IVisual visual)
 {
     return visual.GetVisualAncestors()
         .OfType<AdornerDecorator>()
         .FirstOrDefault()
         ?.AdornerLayer;
 }

 public void StartVisuals()
 { 
     ParticleSystem ps = Instantiate(VFXPool.Instance.Sprays[SpellInformation.Elements[0].ToString()], StaffTransform.position, StaffTransform.rotation) as ParticleSystem;
     ps.transform.SetParent(StaffTransform);
     particleSystemAnchor = ps.GetComponent<IVisual>();
     particleSystemAnchor.AuthorizeCollisionDetection(ref SpellInformation);
 }

 /// <summary>
 /// Renders the specified visual with the specified transform and clip.
 /// </summary>
 /// <param name="visual">The visual to render.</param>
 /// <param name="handle">An optional platform-specific handle.</param>
 /// <param name="transform">The transform.</param>
 /// <param name="clip">An optional clip rectangle.</param>
 public virtual void Render(IVisual visual, IPlatformHandle handle, Matrix transform, Rect? clip = null)
 {
     using (var context = CreateDrawingContext(handle))
     using (clip.HasValue ? context.PushClip(clip.Value) : null)
     {
         Render(visual, context, Matrix.Identity, transform);
     }
 }

 /// <summary>
 /// Invalidates the render for the specified visual and raises <see cref="RenderNeeded"/>.
 /// </summary>
 /// <param name="visual">The visual.</param>
 public void InvalidateRender(IVisual visual)
 {
     if (!_renderQueued)
     {
         _renderNeeded.OnNext(Unit.Default);
         _renderQueued = true;
     }
 }

 private static bool IsHitTestVisible(IVisual visual)
 {
     var element = visual as IInputElement;
     return element != null &&
            element.IsVisible &&
            element.IsHitTestVisible &&
            element.IsEnabledCore;
 }

        /// <summary>
        /// Renders the specified visual.
        /// </summary>
        /// <param name="visual">The visual to render.</param>
        /// <param name="handle">An optional platform-specific handle.</param>
        public virtual void Render(IVisual visual, IPlatformHandle handle)
        {
            using (var context = this.CreateDrawingContext(handle))
            {
                this.Render(visual, context, Matrix.Identity, Matrix.Identity);
            }

            ++this.RenderCount;
        }

        private static IVisual GetVisualParent(IVisual from, IVisual to)
        {
            var p1 = (from ?? to).VisualParent;
            var p2 = (to ?? from).VisualParent;

            if (p1 != null && p2 != null && p1 != p2)
            {
                throw new ArgumentException("Controls for PageSlide must have same parent.");
            }

            return p1;
        }

        public Point GetPosition(IVisual relativeTo)
        {
            Point p = Position;
            IVisual v = relativeTo;

            while (v != null)
            {
                p -= v.Bounds.Position;
                v = v.VisualParent;
            }

            return p;
        }

        /// <summary>
        /// Initializes a new instance of the Core class.
        /// </summary>
        public Core(IVisual visual)
        {
            this.visual = visual;
            physics = new Physics(this);

            FPS = defaultFPS;
            refreshTimer.Tick += (sender, e) =>
                {
                    if (visual.Visible)
                    {
                        lock (this) { visual.Refresh(); }
                    }
                };
            refreshTimer.Start();
            physics.StartSimulation(FPS);
        }

        /// <summary>
        /// Starts the animation.
        /// </summary>
        /// <param name="from">
        /// The control that is being transitioned away from. May be null.
        /// </param>
        /// <param name="to">
        /// The control that is being transitioned to. May be null.
        /// </param>
        /// <returns>
        /// A <see cref="Task"/> that tracks the progress of the animation.
        /// </returns>
        public async Task Start(IVisual from, IVisual to)
        {
            var tasks = new List<Task>();

            if (to != null)
            {
                to.Opacity = 0;
            }

            if (from != null)
            {
                tasks.Add(Animate.Property(
                    (IAvaloniaObject)from,
                    Visual.OpacityProperty,
                    from.Opacity,
                    0,
                    LinearEasing.For<double>(),
                    Duration).ToTask());
            }

            if (to != null)
            {
                to.Opacity = 0;
                to.IsVisible = true;

                tasks.Add(Animate.Property(
                    (IAvaloniaObject)to,
                    Visual.OpacityProperty,
                    0,
                    1,
                    LinearEasing.For<double>(),
                    Duration).ToTask());
            }

            await Task.WhenAll(tasks.ToArray());

            if (from != null)
            {
                from.IsVisible = false;
                from.Opacity = 1;
            }

            if (to != null)
            {
                to.Opacity = 1;
            }
        }

        /// <summary>
        /// Gets the root of the control's visual tree and the position of the control 
        /// in the root's coordinate space.
        /// </summary>
        /// <param name="v">The visual.</param>
        /// <returns>A tuple containing the root and the position of the control.</returns>
        private static Tuple<IRenderRoot, Vector> GetRootAndPosition(IVisual v)
        {
            var result = new Vector();

            while (!(v is IRenderRoot))
            {
                result = new Vector(result.X + v.Bounds.X, result.Y + v.Bounds.Y);
                v = v.VisualParent;

                if (v == null)
                {
                    throw new InvalidOperationException("Control is not attached to visual tree.");
                }
            }

            return Tuple.Create((IRenderRoot)v, result);
        }

        private static void PrintVisualTree(IVisual visual, StringBuilder builder, int indent)
        {
            Control control = visual as Control;

            builder.Append(Indent(indent - 1));

            if (indent > 0)
            {
                builder.Append(" +- ");
            }

            builder.Append(visual.GetType().Name);

            if (control != null)
            {
                builder.Append(" ");
                builder.AppendLine(control.Classes.ToString());

                foreach (var property in AvaloniaPropertyRegistry.Instance.GetRegistered(control))
                {
                    var value = control.GetDiagnostic(property);

                    if (value.Priority != BindingPriority.Unset)
                    {
                        builder.Append(Indent(indent));
                        builder.Append(" |  ");
                        builder.Append(value.Property.Name);
                        builder.Append(" = ");
                        builder.Append(value.Value ?? "(null)");
                        builder.Append(" [");
                        builder.Append(value.Priority);
                        builder.AppendLine("]");
                    }
                }
            }
            else
            {
                builder.AppendLine();
            }

            foreach (var child in visual.VisualChildren)
            {
                PrintVisualTree(child, builder, indent + 1);
            }
        }

        public VisualTreeNode(IVisual visual)
            : base((Control)visual)
        {
            var host = visual as IVisualTreeHost;

            if (host?.Root == null)
            {
                Children = visual.VisualChildren.CreateDerivedCollection(x => new VisualTreeNode(x));
            }
            else
            {
                Children = new ReactiveList<VisualTreeNode>(new[] { new VisualTreeNode(host.Root) });
            }

            if (Control != null)
            {
                IsInTemplate = Control.TemplatedParent != null;
            }
        }

        /// <summary>
        /// Starts the animation.
        /// </summary>
        /// <param name="from">
        /// The control that is being transitioned away from. May be null.
        /// </param>
        /// <param name="to">
        /// The control that is being transitioned to. May be null.
        /// </param>
        /// <param name="forward">
        /// If true, the new page is slid in from the right, or if false from the left.
        /// </param>
        /// <returns>
        /// A <see cref="Task"/> that tracks the progress of the animation.
        /// </returns>
        public async Task Start(IVisual from, IVisual to, bool forward)
        {
            var tasks = new List<Task>();
            var parent = GetVisualParent(from, to);
            var distance = parent.Bounds.Width;

            if (from != null)
            {
                var transform = new TranslateTransform();
                from.RenderTransform = transform;
                tasks.Add(Animate.Property(
                    transform,
                    TranslateTransform.XProperty,
                    0.0,
                    forward ? -distance : distance,
                    LinearEasing.For<double>(),
                    Duration).ToTask());
            }

            if (to != null)
            {
                var transform = new TranslateTransform();
                to.RenderTransform = transform;
                to.IsVisible = true;
                tasks.Add(Animate.Property(
                    transform,
                    TranslateTransform.XProperty,
                    forward ? distance : -distance,
                    0.0,
                    LinearEasing.For<double>(),
                    Duration).ToTask());
            }

            await Task.WhenAll(tasks.ToArray());

            if (from != null)
            {
                from.IsVisible = false;
            }
        }

        /// <summary>
        /// Ensures a visual child is not null and not already parented.
        /// </summary>
        /// <param name="c">The visual child.</param>
        private static void ValidateVisualChild(IVisual c)
        {
            if (c == null)
            {
                throw new ArgumentNullException("Cannot add null to VisualChildren.");
            }

            if (c.VisualParent != null)
            {
                throw new InvalidOperationException("The control already has a visual parent.");
            }
        }

 private IInteractive GetSource(IVisual hit)
 {
     return Captured ??
         (hit as IInteractive) ??
         hit.GetSelfAndVisualAncestors().OfType<IInteractive>().FirstOrDefault();
 }

 /// <summary>
 /// Ensures a visual child is not null.
 /// </summary>
 /// <param name="c">The visual child.</param>
 private static void ValidateLogicalChild(IVisual c)
 {
     if (c == null)
     {
         throw new ArgumentNullException("Cannot add null to VisualChildren.");
     }
 }

        /// <summary>
        /// Gets the visual offset from the specified ancestor.
        /// </summary>
        /// <param name="ancestor">The ancestor visual.</param>
        /// <param name="visual">The visual.</param>
        /// <returns>The visual offset.</returns>
        private static Vector GetOffsetFrom(IVisual ancestor, IVisual visual)
        {
            var result = new Vector();

            while (visual != ancestor)
            {
                result = new Vector(result.X + visual.Bounds.X, result.Y + visual.Bounds.Y);
                visual = visual.VisualParent;

                if (visual == null)
                {
                    throw new ArgumentException("'visual' is not a descendent of 'ancestor'.");
                }
            }

            return result;
        }