SkewY.cs

using System.Threading.Tasks;
using System.Xml;
using SkiaSharp;
using Waher.Layout.Layout2D.Model.Attributes;
 
namespace Waher.Layout.Layout2D.Model.Transforms
{
    public class SkewY : PivotTrasformation
    {
        private FloatAttribute factor;
 
        public SkewY(Layout2DDocument Document, ILayoutElement Parent)
            : base(Document, Parent)
        {
        }
 
        public override string LocalName => "SkewY";
 
        public FloatAttribute FactorAttribute
        {
            get => this.factor;
            set => this.factor = value;
        }
 
        public override Task FromXml(XmlElement Input)
        {
            this.factor = new FloatAttribute(Input, "factor", this.Document);
            return base.FromXml(Input);
        }
 
        public override void ExportAttributes(XmlWriter Output)
        {
            base.ExportAttributes(Output);
 
            this.factor?.Export(Output);
        }
 
        public override ILayoutElement Create(Layout2DDocument Document, ILayoutElement Parent)
        {
            return new SkewY(Document, Parent);
        }
 
        public override void CopyContents(ILayoutElement Destination)
        {
            base.CopyContents(Destination);
 
            if (Destination is SkewY Dest)
                Dest.factor = this.factor?.CopyIfNotPreset(Destination.Document);
        }
 
        public override async Task AfterMeasureDimensions(DrawingState State)
        {
            await base.AfterMeasureDimensions(State);
 
            EvaluationResult<float> Factor = await this.factor.TryEvaluate(State.Session);
            if (Factor.Ok)
            {
                this.sy = Factor.Result;
 
                SKMatrix M = SKMatrix.CreateTranslation(this.xCoordinate, this.yCoordinate);
                M = M.PreConcat(SKMatrix.CreateSkew(0, this.sy));
                M = M.PreConcat(SKMatrix.CreateTranslation(-this.xCoordinate, -this.yCoordinate));
 
                this.TransformBoundingBox(M);
            }
            else
                this.sy = 0;
        }
 
        private float sy;
 
        public override async Task Draw(DrawingState State)
        {
            SKMatrix M = State.Canvas.TotalMatrix;
            State.Canvas.Translate(this.xCoordinate, this.yCoordinate);
            State.Canvas.Skew(0, this.sy);
            State.Canvas.Translate(-this.xCoordinate, -this.yCoordinate);
 
            await base.Draw(State);
 
            State.Canvas.SetMatrix(M);
        }
 
        public override void ExportStateAttributes(XmlWriter Output)
        {
            base.ExportStateAttributes(Output);
 
            this.factor?.ExportState(Output);
        }
 
    }
}