Plot2DLayeredAreaPainter.cs

using System;
using SkiaSharp;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Abstraction.Sets;
using Waher.Script.Objects;
using Waher.Script.Operators.Vectors;
 
namespace Waher.Script.Graphs.Functions.Plots
{
    public class Plot2DLayeredAreaPainter : SingleColorGraphPainter, IPainter2D
    {
        public void DrawGraph(SKCanvas Canvas, SKPoint[] Points, object[] Parameters, SKPoint[] PrevPoints, object[] PrevParameters,
            DrawingArea DrawingArea)
        {
            SKPaint Brush = null;
            SKPath Path = null;
            bool First = true;
 
            try
            {
                Brush = new SKPaint()
                {
                    Style = SKPaintStyle.Fill,
                    Color = Graph.ToColor(Parameters[0])
                };
                Path = new SKPath();
 
                foreach (SKPoint Point in Points)
                {
                    if (First)
                    {
                        First = false;
                        Path.MoveTo(Point);
                    }
                    else
                        Path.LineTo(Point);
                }
 
                IElement Zero;
                ISet Set = DrawingArea.MinY.AssociatedSet;
 
                if (Set is IGroup Group)
                    Zero = Group.AdditiveIdentity;
                else
                    Zero = new DoubleNumber(0);
 
                IVector XAxis = VectorDefinition.Encapsulate(new IElement[] { DrawingArea.MinX, DrawingArea.MaxX }, false, null) as IVector;
                IVector YAxis = VectorDefinition.Encapsulate(new IElement[] { Zero, Zero }, false, null) as IVector;
 
                PrevPoints = DrawingArea.Scale(XAxis, YAxis);
 
                if (DrawingArea.MinX.AssociatedObjectValue is string && 
                    DrawingArea.MaxX.AssociatedObjectValue is string)
                {
                    PrevPoints[0].X = Points[0].X;
                    PrevPoints[1].X = Points[Points.Length - 1].X;
                }
 
                int i = PrevPoints.Length;
 
                while (--i >= 0)
                    Path.LineTo(PrevPoints[i]);
 
                Path.LineTo(Points[0]);
 
                Canvas.DrawPath(Path, Brush);
            }
            finally
            {
                Brush?.Dispose();
                Path?.Dispose();
            }
        }
 
    }
}