aistudio-wpf-diagram/AIStudio.Wpf.DiagramDesigner/ViewModels/BaseViewModel/ConnectorLabelModel.cs

using System.Linq;
using AIStudio.Wpf.DiagramDesigner.Geometrys;
using SvgPathProperties;

namespace AIStudio.Wpf.DiagramDesigner
{
    public class ConnectorLabelModel : ConnectorPointModel, ISelectable
    {
        public ConnectorLabelModel(ConnectorViewModel connector, string content, double? distance = null, PointBase? offset = null)
        {
            Parent = connector;
            Text = content;
            Distance = distance;
            Offset = offset ?? new PointBase();         
        }

        protected override void Init()
        {
            base.Init();

            DeleteLabelCommand = new SimpleCommand(DeleteLabel);
        }

        #region 属性
        public ConnectorViewModel Connector
        {
            get
            {
                return Parent as ConnectorViewModel;
            }
        }

        /// <summary>
        /// 3 types of values are possible:
        /// <para>- A number between 0 and 1: Position relative to the link's length</para>
        /// <para>- A positive number, greater than 1: Position away from the start</para>
        /// <para>- A negative number, less than 0: Position away from the end</para>
        /// </summary>
        public double? Distance
        {
            get; set;
        }
        public PointBase Offset
        {
            get; set;
        }

        //private bool _isSelected;
        public override bool IsSelected
        {
            get
            {
                return _isSelected;
            }
            set
            {
                if (SetProperty(ref _isSelected, value))
                {
                    //如果没有文字，失去焦点自动清除
                    if (_isSelected == false && string.IsNullOrEmpty(Text))
                    {
                        Connector.Labels.Remove(this);
                    }
                }

            }
        }

        public SimpleCommand DeleteLabelCommand
        {
            get; set;
        }
        #endregion

        private bool updating = false;

        public void UpdatePosition(SvgPath[] paths)
        {
            var position = FindPosition(paths);
            if (position == null)
                return;

            updating = true;
            X = position.Value.X;
            Y = position.Value.Y;
            updating = false;
        }

        public PointBase? FindPosition(SvgPath[] paths)
        {
            var totalLength = paths.Sum(p => p.Length);

            double length;


            if (Distance >= 0 && Distance <= 1)
            {
                length = Distance.Value * totalLength;
            }
            else if (Distance > 1)
            {
                length = Distance.Value;
            }
            else if (Distance < 0)
            {
                length = totalLength + Distance.Value;
            }
            else
            {
                length = totalLength * (Connector.Labels.IndexOf(this) + 1) / (Connector.Labels.Count + 1);
            }


            foreach (var path in paths)
            {
                var pathLength = path.Length;
                if (length < pathLength)
                {
                    var pt = path.GetPointAtLength(length);
                    return new PointBase(pt.X + Offset.X, pt.Y + Offset.Y);
                }

                length -= pathLength;
            }

            return null;
        }

        public void UpdateOffsetX(double oldvalue, double newvalue)
        {
            if (updating == true) return;

            Offset += new VectorBase(newvalue - oldvalue, 0);
        }

        public void UpdateOffsetY(double oldvalue, double newvalue)
        {
            if (updating == true) return;

            Offset += new VectorBase(0, newvalue - oldvalue);
        }

        public override void AddToSelection(bool selected)
        {
            foreach (var item in Connector.Labels.ToList())
                item.IsSelected = false;

            if (selected == true)
            {
                IsSelected = true;
            }
        }

        private void DeleteLabel(object parameter)
        {
            if (parameter is ConnectorLabelModel label)
            {
                Connector.Labels.Remove(label);
            }
        }

    }
}