HandyControl/src/Shared/HandyControl_Shared/Expression/Shapes/PrimitiveShape.cs

using System;
using System.Windows;
using System.Windows.Media;
using System.Windows.Shapes;
using HandyControl.Data;
using HandyControl.Expression.Drawing;
using HandyControl.Expression.Media;

namespace HandyControl.Expression.Shapes
{
    public abstract class PrimitiveShape : Shape, IGeometrySourceParameters, IShape
    {
        private IGeometrySource _geometrySource;

        static PrimitiveShape()
        {
            StretchProperty.OverrideMetadata(typeof(PrimitiveShape),
                new DrawingPropertyMetadata(Stretch.Fill, DrawingPropertyMetadataOptions.AffectsRender));
            StrokeThicknessProperty.OverrideMetadata(typeof(PrimitiveShape),
                new DrawingPropertyMetadata(ValueBoxes.Double1Box, DrawingPropertyMetadataOptions.AffectsRender));
        }

        protected sealed override Geometry DefiningGeometry =>
            GeometrySource.Geometry ?? Geometry.Empty;

        private IGeometrySource GeometrySource => _geometrySource ?? (_geometrySource = CreateGeometrySource());

        Stretch IGeometrySourceParameters.Stretch => Stretch;

        Brush IGeometrySourceParameters.Stroke => Stroke;

        double IGeometrySourceParameters.StrokeThickness => StrokeThickness;

        public event EventHandler RenderedGeometryChanged;

        public void InvalidateGeometry(InvalidateGeometryReasons reasons)
        {
            if (GeometrySource.InvalidateGeometry(reasons)) InvalidateArrange();
        }

        public Thickness GeometryMargin => GeometrySource.LogicalBounds.Subtract(RenderedGeometry.Bounds);

        Brush IShape.Fill
        {
            get => Fill;
            set => Fill = value;
        }

        Stretch IShape.Stretch
        {
            get => Stretch;
            set => Stretch = value;
        }

        Brush IShape.Stroke
        {
            get => Stroke;
            set => Stroke = value;
        }

        double IShape.StrokeThickness
        {
            get => StrokeThickness;
            set => StrokeThickness = value;
        }

        protected override Size ArrangeOverride(Size finalSize)
        {
            if (GeometrySource.UpdateGeometry(this, finalSize.Bounds())) RealizeGeometry();
            base.ArrangeOverride(finalSize);
            return finalSize;
        }

        protected abstract IGeometrySource CreateGeometrySource();

        protected override Size MeasureOverride(Size availableSize) => new Size(base.StrokeThickness, base.StrokeThickness);

        private void RealizeGeometry() => RenderedGeometryChanged?.Invoke(this, EventArgs.Empty);
    }
}