inabox/InABox.Avalonia/Components/ImageEditor/ImageEditor.axaml.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Shapes;
using Avalonia.Data;
using Avalonia.Input;
using Avalonia.Markup.Xaml;
using Avalonia.Media;
using CommunityToolkit.Mvvm.Input;
using InABox.Avalonia.Components.ImageEditing;
using System.Collections.ObjectModel;

namespace InABox.Avalonia.Components;

public enum ImageEditingMode
{
    Polyline
}

// TODO: Make it so we don't re-render everything everytime 'Objects' changes.

public partial class ImageEditor : UserControl
{
    public static readonly StyledProperty<IImage?> SourceProperty =
        AvaloniaProperty.Register<ImageEditor, IImage?>(nameof(Source));

    public static readonly StyledProperty<IBrush?> PrimaryBrushProperty =
        AvaloniaProperty.Register<ImageEditor, IBrush?>(nameof(PrimaryBrush), new SolidColorBrush(Colors.Black));

    public IImage? Source
    {
        get => GetValue(SourceProperty);
        set => SetValue(SourceProperty, value);
    }

    #region Editing Properties

    public ImageEditingMode Mode { get; set; } = ImageEditingMode.Polyline;

    public IBrush? PrimaryBrush
    {
        get => GetValue(PrimaryBrushProperty);
        set => SetValue(PrimaryBrushProperty, value);
    }

    public double LineThickness { get; set; } = 1.0;

    #endregion

    private ObservableCollection<IImageEditorObject> Objects = new();

    private IImageEditorObject? CurrentObject;

    private Stack<IImageEditorObject> RedoStack = new();

    public ImageEditor()
    {
        InitializeComponent();

        Objects.CollectionChanged += Objects_CollectionChanged;

        SetMode(Mode);
    }

    #region Editing Commands

    private void Undo()
    {
        RedoStack.Push(Objects[^1]);
        Objects.RemoveAt(Objects.Count - 1);
    }

    private void Redo()
    {
        if (!RedoStack.TryPop(out var top)) return;

        Objects.Add(top);
    }

    private void AddObject(IImageEditorObject obj)
    {
        Objects.Add(obj);
        RedoStack.Clear();
    }

    [RelayCommand]
    private void SetMode(ImageEditingMode mode)
    {
        Mode = mode;
        switch (mode)
        {
            case ImageEditingMode.Polyline:
                var line = new Polyline
                {
                    Points = [new(0, 0), new(20, 8), new(5, 16), new(25, 25)],
                    Width = 25,
                    Height = 25
                };
                line.Bind(Polyline.StrokeProperty, new Binding(nameof(PrimaryBrush)) { Source = this });
                ShapeButton.Content = line;
                break;
        }
    }

    #endregion

    private void Objects_CollectionChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        Canvas.Children.Clear();
        foreach(var item in Objects)
        {
            item.Update();
            Canvas.Children.Add(item.GetControl());
        }
    }

    Point ConvertToImageCoordinates(Point canvasCoordinates)
    {
        return canvasCoordinates;
    }

    private void Canvas_PointerPressed(object? sender, PointerPressedEventArgs e)
    {
        var position = ConvertToImageCoordinates(e.GetPosition(Canvas));
        switch (Mode)
        {
            case ImageEditingMode.Polyline:
                CurrentObject = new PolylineObject
                {
                    Points = [position],
                    PrimaryBrush = PrimaryBrush,
                    Thickness = LineThickness
                };
                AddObject(CurrentObject);
                break;
        }
    }

    private void Canvas_PointerMoved(object? sender, PointerEventArgs e)
    {
        var position = ConvertToImageCoordinates(e.GetPosition(Canvas));
        if(CurrentObject is PolylineObject polyline)
        {
            polyline.Points.Add(position);
            polyline.Update();
        }
    }

    private void Canvas_PointerReleased(object? sender, PointerReleasedEventArgs e)
    {
        var position = ConvertToImageCoordinates(e.GetPosition(Canvas));
        if(CurrentObject is PolylineObject polyline)
        {
            polyline.Points.Add(position);
            polyline.Update();
            CurrentObject = null;
        }

    }
}