qamp/Qrakhen.Qamp.Editor/Controls/Caret.cs

using System.Windows;
using System.Windows.Documents;
using System.Windows.Media;
using System.Windows.Threading;

namespace Qrakhen.Qamp.Editor.Controls;

public class Caret : Adorner
{
   private readonly Pen _pen;
   private readonly double _height;
   private readonly Brush _brush;
   private bool _blink;
   private bool _enabled;
   private Point _cursorPosition;
   private Point _targetPosition;
   private (Point from, Point to)[] _lines = [];
   private DispatcherTimer _blinkTimer;
   private DispatcherTimer _moveTimer;

   public Caret(UIElement adornedElement, Brush brush, double height = 18, double thickness = 1.72) : base(adornedElement)
   {
      IsHitTestVisible = false;

      _enabled = true;
      _height = height;
      _brush = brush;
      _pen = new Pen(brush, 1.92);

      _blinkTimer = new DispatcherTimer();
      _blinkTimer.Interval = TimeSpan.FromMilliseconds(324);
      _blinkTimer.Tick += new EventHandler((s, e) => {
         Toggle(_blink = !_blink);
      });
      _blinkTimer.Start();

      _moveTimer = new DispatcherTimer();
      _moveTimer.Interval = TimeSpan.FromMilliseconds(12);
      _moveTimer.Tick += new EventHandler((s, e) => {
         var delta = _targetPosition - _cursorPosition;
         if (delta.Length > 2.4)
            _cursorPosition += delta * .84;
         else {
            _cursorPosition = _targetPosition;
            _moveTimer.Stop();
            _blinkTimer.Start();
         }
         InvalidateVisual();
      });
   }

   public void Toggle(bool hide)
   {
      _pen.Brush = hide ? Brushes.Transparent : _brush;
      InvalidateVisual();
   }

   public void Disable()
   {
      _blinkTimer?.Stop();
      _enabled = false;
      Toggle(true);
      InvalidateVisual();
   }

   public void UpdateSelection((Point from, Point to)[] lines)
   {
      _lines = lines;
      InvalidateVisual();
   }

   public void UpdatePosition(Point newPosition)
   {
      _cursorPosition = _targetPosition = newPosition;
      _enabled = true;
      Toggle(_blink = false);
      _blinkTimer.Start();
   }

   protected override void OnRender(DrawingContext drawingContext)
   {
      Point startPoint = new(_cursorPosition.X, _cursorPosition.Y);
      Point endPoint = new(_cursorPosition.X, _cursorPosition.Y + _height);
      drawingContext.DrawLine(_pen, startPoint, endPoint);
   }
}