inabox/InABox.Avalonia/Components/ImageEditor/Objects/DimensionObject.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Controls.Shapes;
using Avalonia.Input;
using Avalonia.Media;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace InABox.Avalonia.Components.ImageEditing;

internal class DimensionObject : IImageEditorObject
{
    public IBrush? PrimaryBrush { get; set; }

    public Point Point1 { get; set; }

    public Point Point2 { get; set; }

    public double LineThickness { get; set; }

    public string Text { get; set; } = "";

    public double Offset { get; set; } = 10;

    public bool Complete { get; set; } = false;

    private Canvas Control = new();

    private Thumb? Thumb;

    private bool _active = true;

    public Control GetControl() => Control;

    private Vector GetMainVec()
    {
        var p1 = new Vector(Point1.X, Point1.Y);
        var p2 = new Vector(Point2.X, Point2.Y);

        var mainVec = p2 - p1;
        var length = mainVec.Length;
        if(length == 0)
        {
            mainVec = new Vector(0, 0);
        }
        else
        {
            mainVec /= length;
        }

        return mainVec;
    }

    private Vector GetPerpVec()
    {
        var mainVec = GetMainVec();
        return new Vector(mainVec.Y, -mainVec.X);
    }

    public void Update()
    {
        Control.Children.RemoveAll(Control.Children.Where(x => !(x is Thumb)));

        Point Point(Vector v) => new(v.X, v.Y);

        var p1 = new Vector(Point1.X, Point1.Y);
        var p2 = new Vector(Point2.X, Point2.Y);

        var mainVec = p2 - p1;
        var length = mainVec.Length;
        if(length == 0)
        {
            mainVec = new Vector(0, 0);
        }
        else
        {
            mainVec /= length;
        }
        var perpVec = new Vector(mainVec.Y, -mainVec.X);

        var arrowLength = LineThickness * 2;
        var offset = perpVec * Offset;

        var mainLines = new List<Line>()
        {
            new()
            {
                StartPoint = Point(p1 + offset),
                EndPoint = Point(p2 + offset),
                StrokeLineCap = PenLineCap.Round
            },
            new()
            {
                StartPoint = Point(p1 + offset),
                EndPoint = Point(p1 + mainVec * arrowLength + perpVec * arrowLength + offset),
                StrokeLineCap = PenLineCap.Square
            },
            new()
            {
                StartPoint = Point(p1 + offset),
                EndPoint = Point(p1 + mainVec * arrowLength - perpVec * arrowLength + offset),
                StrokeLineCap = PenLineCap.Square
            },
            new()
            {
                StartPoint = Point(p2 + offset),
                EndPoint = Point(p2 - mainVec * arrowLength + perpVec * arrowLength + offset),
                StrokeLineCap = PenLineCap.Square
            },
            new()
            {
                StartPoint = Point(p2 + offset),
                EndPoint = Point(p2 - mainVec * arrowLength - perpVec * arrowLength + offset),
                StrokeLineCap = PenLineCap.Square
            }
        };

        var dotLines = new List<Line>()
        {
            new()
            {
                StartPoint = Point(p1),
                EndPoint = Point(p1 + offset)
            },
            new()
            {
                StartPoint = Point(p2),
                EndPoint = Point(p2 + offset)
            },
        };

        foreach (var line in dotLines)
        {
            line.StrokeThickness = LineThickness;
            line.Stroke = PrimaryBrush;
            line.StrokeDashArray = [2, 2];
            Control.Children.Add(line);
        }

        foreach (var line in mainLines)
        {
            line.StrokeThickness = LineThickness;
            line.Stroke = PrimaryBrush;
            Control.Children.Add(line);
        }

        var textHeight = 20;

        var text = new TextBlock
        {
            Text = Text,
            FontSize = textHeight,
            TextAlignment = TextAlignment.Center,
            Width = length,
            Foreground = PrimaryBrush
        };
        text.RenderTransform = new RotateTransform(Math.Atan2(mainVec.Y, mainVec.X) * 180 / Math.PI);
        var textPos = p1 + offset + mainVec * length / 2 + perpVec * (textHeight / 2 + 5);
        Canvas.SetLeft(text, textPos.X - length / 2);
        Canvas.SetTop(text, textPos.Y - textHeight / 2);

        Control.Children.Add(text);

        if(Thumb is null && _active && length > 0)
        {
            Thumb = new();
            Thumb.Width = 10;
            Thumb.Height = 10;
            Thumb.Cursor = new(StandardCursorType.SizeAll);
            Thumb.DragDelta += Thumb_DragDelta;
            Thumb.ZIndex = 1;

            Control.Children.Add(Thumb);
        }

        if(Thumb is not null)
        {
            Thumb.RenderTransform = new RotateTransform(Math.Atan2(mainVec.Y, mainVec.X) * 180 / Math.PI);

            var thumbPos = p1 + offset + mainVec * length / 2;
            Canvas.SetLeft(Thumb, thumbPos.X - 5);
            Canvas.SetTop(Thumb, thumbPos.Y - 5);
        }
    }

    private Vector Rotate(Vector v, double angle)
    {
        angle = Math.Atan2(v.Y, v.X) + angle;
        var length = v.Length;
        return new Vector(
            length * Math.Cos(angle),
            length * Math.Sin(angle));
    }

    private void Thumb_DragDelta(object? sender, VectorEventArgs e)
    {
        var main = GetMainVec();
        var v = Vector.Dot(Rotate(e.Vector, Math.Atan2(main.Y, main.X)), GetPerpVec());
        Offset += v;
        Update();
    }

    public void SetActive(bool active)
    {
        _active = active;
        if(Thumb is not null)
        {
            Control.Children.Remove(Thumb);
            Thumb = null;
        }
    }
}