ShrlAlgoToolkit/WPFDark/Controls/BiaClippingBorder.xaml.cs

using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using WPFDark.Internals;

namespace WPFDark.Controls
{
    // https://stackoverflow.com/questions/324641/how-to-make-the-contents-of-a-round-cornered-border-be-also-round-cornered
    public class BiaClippingBorder : Border
    {
        protected override void OnRender(DrawingContext dc)
        {
            OnApplyChildClip();
            base.OnRender(dc);
        }

        public override UIElement Child
        {
            get => base.Child;

            set
            {
                if (Child == value)
                    return;

                Child?.SetValue(ClipProperty, _oldClip);

                _oldClip = value?.ReadLocalValue(ClipProperty);

                base.Child = value;
            }
        }

        static BiaClippingBorder()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(BiaClippingBorder),
                new FrameworkPropertyMetadata(typeof(BiaClippingBorder)));
        }

        protected virtual void OnApplyChildClip()
        {
            var child = Child;

            if (child is null)
                return;

            var key = HashCodeMaker.Make(
                Child.RenderSize.Width, Child.RenderSize.Height,
                CornerRadius.BottomLeft, CornerRadius.BottomRight,
                CornerRadius.TopLeft, CornerRadius.TopRight);

            if (_clipRectCache.TryGetValue(key, out var clipRect) == false)
            {
                var isSame =
                    NumberHelper.AreClose(CornerRadius.TopLeft, CornerRadius.TopRight) &&
                    NumberHelper.AreClose(CornerRadius.TopRight, CornerRadius.BottomRight) &&
                    NumberHelper.AreClose(CornerRadius.BottomRight, CornerRadius.BottomLeft) &&
                    NumberHelper.AreClose(CornerRadius.BottomLeft, CornerRadius.TopLeft);

                clipRect = isSame
                    ? MakeRoundRectangleGeometrySameCorner(new Rect(Child.RenderSize), CornerRadius, BorderThickness)
                    : MakeRoundRectangleGeometry(new Rect(Child.RenderSize), CornerRadius, BorderThickness);

                _clipRectCache.Add(key, clipRect);
            }

            child.Clip = clipRect;
        }

        private object? _oldClip;

        private static readonly Dictionary<long, Geometry> _clipRectCache = new Dictionary<long, Geometry>();

        private static Geometry MakeRoundRectangleGeometrySameCorner(Rect baseRect, CornerRadius cornerRadius,
            Thickness borderThickness)
        {
            var radius = (0.0, cornerRadius.TopLeft - borderThickness.Left * 0.5).Max();

            var clipRect = new RectangleGeometry
            {
                RadiusX = radius,
                RadiusY = radius,
                Rect = baseRect
            };

            clipRect.Freeze();

            return clipRect;
        }

        // https://wpfspark.wordpress.com/2011/06/08/clipborder-a-wpf-border-that-clips/
        private static Geometry MakeRoundRectangleGeometry(Rect baseRect, CornerRadius cornerRadius, Thickness borderThickness)
        {
            if (cornerRadius.TopLeft < double.Epsilon)
                cornerRadius.TopLeft = 0.0;

            if (cornerRadius.TopRight < double.Epsilon)
                cornerRadius.TopRight = 0.0;

            if (cornerRadius.BottomLeft < double.Epsilon)
                cornerRadius.BottomLeft = 0.0;

            if (cornerRadius.BottomRight < double.Epsilon)
                cornerRadius.BottomRight = 0.0;

            var leftHalf = borderThickness.Left * 0.5;
            if (leftHalf < double.Epsilon)
                leftHalf = 0.0;

            var topHalf = borderThickness.Top * 0.5;
            if (topHalf < double.Epsilon)
                topHalf = 0.0;

            var rightHalf = borderThickness.Right * 0.5;
            if (rightHalf < double.Epsilon)
                rightHalf = 0.0;

            var bottomHalf = borderThickness.Bottom * 0.5;
            if (bottomHalf < double.Epsilon)
                bottomHalf = 0.0;

            var topLeftRect = new Rect(
                baseRect.Location.X,
                baseRect.Location.Y,
                (0.0, cornerRadius.TopLeft - leftHalf).Max(),
                (0.0, cornerRadius.TopLeft - rightHalf).Max());

            var topRightRect = new Rect(
                baseRect.Location.X + baseRect.Width - cornerRadius.TopRight + rightHalf,
                baseRect.Location.Y,
                (0.0, cornerRadius.TopRight - rightHalf).Max(),
                (0.0, cornerRadius.TopRight - topHalf).Max());

            var bottomRightRect = new Rect(
                baseRect.Location.X + baseRect.Width - cornerRadius.BottomRight + rightHalf,
                baseRect.Location.Y + baseRect.Height - cornerRadius.BottomRight + bottomHalf,
                (0.0, cornerRadius.BottomRight - rightHalf).Max(),
                (0.0, cornerRadius.BottomRight - bottomHalf).Max());

            var bottomLeftRect = new Rect(
                baseRect.Location.X,
                baseRect.Location.Y + baseRect.Height - cornerRadius.BottomLeft + bottomHalf,
                (0.0, cornerRadius.BottomLeft - leftHalf).Max(),
                (0.0, cornerRadius.BottomLeft - bottomHalf).Max());

            if (topLeftRect.Right > topRightRect.Left)
            {
                var newWidth = topLeftRect.Width / (topLeftRect.Width + topRightRect.Width) * baseRect.Width;

                topLeftRect = new Rect(
                    topLeftRect.Location.X,
                    topLeftRect.Location.Y,
                    newWidth,
                    topLeftRect.Height);

                topRightRect = new Rect(
                    baseRect.Left + newWidth,
                    topRightRect.Location.Y,
                    (0.0, baseRect.Width - newWidth).Max(),
                    topRightRect.Height);
            }

            if (topRightRect.Bottom > bottomRightRect.Top)
            {
                var newHeight = topRightRect.Height / (topRightRect.Height + bottomRightRect.Height) * baseRect.Height;

                topRightRect = new Rect(
                    topRightRect.Location.X,
                    topRightRect.Location.Y,
                    topRightRect.Width,
                    newHeight);

                bottomRightRect = new Rect(
                    bottomRightRect.Location.X,
                    baseRect.Top + newHeight,
                    bottomRightRect.Width,
                    (0.0, baseRect.Height - newHeight).Max());
            }

            if (bottomRightRect.Left < bottomLeftRect.Right)
            {
                var newWidth = bottomLeftRect.Width / (bottomLeftRect.Width + bottomRightRect.Width) * baseRect.Width;

                bottomLeftRect = new Rect(
                    bottomLeftRect.Location.X,
                    bottomLeftRect.Location.Y,
                    newWidth,
                    bottomLeftRect.Height);

                bottomRightRect = new Rect(
                    baseRect.Left + newWidth,
                    bottomRightRect.Location.Y,
                    (0.0, baseRect.Width - newWidth).Max(),
                    bottomRightRect.Height);
            }

            if (bottomLeftRect.Top < topLeftRect.Bottom)
            {
                var newHeight = topLeftRect.Height / (topLeftRect.Height + bottomLeftRect.Height) * baseRect.Height;

                topLeftRect = new Rect(
                    topLeftRect.Location.X,
                    topLeftRect.Location.Y,
                    topLeftRect.Width,
                    newHeight);

                bottomLeftRect = new Rect(
                    bottomLeftRect.Location.X,
                    baseRect.Top + newHeight,
                    bottomLeftRect.Width,
                    (0.0, baseRect.Height - newHeight).Max());
            }

            var clipRect = new StreamGeometry();

            using (var context = clipRect.Open())
            {
                context.BeginFigure(topLeftRect.BottomLeft, true, true);

                context.ArcTo(topLeftRect.TopRight, topLeftRect.Size, 0, false, SweepDirection.Clockwise,
                    true, true);

                context.LineTo(topRightRect.TopLeft, true, true);
                context.ArcTo(topRightRect.BottomRight, topRightRect.Size, 0, false, SweepDirection.Clockwise,
                    true, true);

                context.LineTo(bottomRightRect.TopRight, true, true);
                context.ArcTo(bottomRightRect.BottomLeft, bottomRightRect.Size, 0, false, SweepDirection.Clockwise,
                    true, true);

                context.LineTo(bottomLeftRect.BottomRight, true, true);
                context.ArcTo(bottomLeftRect.TopLeft, bottomLeftRect.Size, 0, false, SweepDirection.Clockwise,
                    true, true);
            }

            clipRect.Freeze();

            return clipRect;
        }
    }
}