Avalonia/src/Avalonia.Visuals/Rendering/SceneGraph/RectangleNode.cs

using System;
using System.Collections.Generic;
using Avalonia.Media;
using Avalonia.Media.Immutable;
using Avalonia.Platform;
using Avalonia.VisualTree;

namespace Avalonia.Rendering.SceneGraph
{
    /// <summary>
    /// A node in the scene graph which represents a rectangle draw.
    /// </summary>
    internal class RectangleNode : BrushDrawOperation
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="RectangleNode"/> class.
        /// </summary>
        /// <param name="transform">The transform.</param>
        /// <param name="brush">The fill brush.</param>
        /// <param name="pen">The stroke pen.</param>
        /// <param name="rect">The rectangle to draw.</param>
        /// <param name="boxShadow">The box shadow parameters</param>
        /// <param name="childScenes">Child scenes for drawing visual brushes.</param>
        public RectangleNode(
            Matrix transform,
            IBrush brush,
            IPen pen,
            RoundedRect rect,
            BoxShadows boxShadows,
            IDictionary<IVisual, Scene> childScenes = null)
            : base(boxShadows.TransformBounds(rect.Rect).Inflate((pen?.Thickness ?? 0) / 2), transform)
        {
            Transform = transform;
            Brush = brush?.ToImmutable();
            Pen = pen?.ToImmutable();
            Rect = rect;
            ChildScenes = childScenes;
            BoxShadows = boxShadows;
        }

        /// <summary>
        /// Gets the transform with which the node will be drawn.
        /// </summary>
        public Matrix Transform { get; }

        /// <summary>
        /// Gets the fill brush.
        /// </summary>
        public IBrush Brush { get; }

        /// <summary>
        /// Gets the stroke pen.
        /// </summary>
        public ImmutablePen Pen { get; }

        /// <summary>
        /// Gets the rectangle to draw.
        /// </summary>
        public RoundedRect Rect { get; }
        
        /// <summary>
        /// The parameters for the box-shadow effect
        /// </summary>
        public BoxShadows BoxShadows { get; }

        /// <inheritdoc/>
        public override IDictionary<IVisual, Scene> ChildScenes { get; }

        /// <summary>
        /// Determines if this draw operation equals another.
        /// </summary>
        /// <param name="transform">The transform of the other draw operation.</param>
        /// <param name="brush">The fill of the other draw operation.</param>
        /// <param name="pen">The stroke of the other draw operation.</param>
        /// <param name="rect">The rectangle of the other draw operation.</param>
        /// <param name="boxShadow">The box shadow parameters of the other draw operation</param>
        /// <returns>True if the draw operations are the same, otherwise false.</returns>
        /// <remarks>
        /// The properties of the other draw operation are passed in as arguments to prevent
        /// allocation of a not-yet-constructed draw operation object.
        /// </remarks>
        public bool Equals(Matrix transform, IBrush brush, IPen pen, RoundedRect rect, BoxShadows boxShadows)
        {
            return transform == Transform &&
                   Equals(brush, Brush) &&
                   Equals(Pen, pen) &&
                   Media.BoxShadows.Equals(BoxShadows, boxShadows) &&
                   rect.Equals(Rect);
        }

        /// <inheritdoc/>
        public override void Render(IDrawingContextImpl context)
        {
            context.Transform = Transform;

            context.DrawRectangle(Brush, Pen, Rect, BoxShadows);
        }

        /// <inheritdoc/>
        public override bool HitTest(Point p)
        {
            // TODO: This doesn't respect CornerRadius yet.
            if (Transform.HasInverse)
            {
                p *= Transform.Invert();

                if (Brush != null)
                {
                    var rect = Rect.Rect.Inflate((Pen?.Thickness / 2) ?? 0);
                    return rect.Contains(p);
                }
                else
                {
                    var borderRect = Rect.Rect.Inflate((Pen?.Thickness / 2) ?? 0);
                    var emptyRect = Rect.Rect.Deflate((Pen?.Thickness / 2) ?? 0);
                    return borderRect.Contains(p) && !emptyRect.Contains(p);
                }
            }

            return false;
        }
    }
}