FontRef.cs

using SkiaSharp;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.Xml;
using Waher.Layout.Layout2D.Model.Attributes;
using Waher.Layout.Layout2D.Model.Fonts;
 
namespace Waher.Layout.Layout2D.Model.Content.FlowingText
{
    public class FontRef : EmbeddedText
    {
        private StringAttribute font;
 
        public FontRef(Layout2DDocument Document, ILayoutElement Parent)
            : base(Document, Parent)
        {
        }
 
        public override string LocalName => "FontRef";
 
        public StringAttribute FontAttribute
        {
            get => this.font;
            set => this.font = value;
        }
 
        public override Task FromXml(XmlElement Input)
        {
            this.font = new StringAttribute(Input, "font", this.Document);
            
            return base.FromXml(Input);
        }
 
        public override void ExportAttributes(XmlWriter Output)
        {
            base.ExportAttributes(Output);
 
            this.font?.Export(Output);
        }
 
        public override ILayoutElement Create(Layout2DDocument Document, ILayoutElement Parent)
        {
            return new FontRef(Document, Parent);
        }
 
        public override void CopyContents(ILayoutElement Destination)
        {
            base.CopyContents(Destination);
 
            if (Destination is FontRef Dest)
                Dest.font = this.font?.CopyIfNotPreset(Destination.Document);
        }
 
        public override async Task MeasureSegments(List<Segment> Segments, DrawingState State)
        {
            EvaluationResult<string> FontId = await this.font.TryEvaluate(State.Session);
 
            if (FontId.Ok && 
                this.Document.TryGetElement(FontId.Result, out ILayoutElement E) && 
                E is Font Font)
            {
                SKFont Bak = State.Font;
                SKPaint Bak2 = State.Text;
 
                State.Font = Font.FontDef;
                State.Text = Font.Text;
 
                await base.MeasureSegments(Segments, State);
 
                State.Font = Bak;
                State.Text = Bak2;
            }
            else
                await base.MeasureSegments(Segments, State);
        }
 
        public override void ExportStateAttributes(XmlWriter Output)
        {
            base.ExportStateAttributes(Output);
 
            this.font?.ExportState(Output);
        }
    }
}