qamp/Qrakhen.Qamp.Editor/Controls/EditorFrame.xaml.cs

using Qrakhen.Qamp.Editor.Primitives;
using Qrakhen.Qamp.Editor.ViewModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;

namespace Qrakhen.Qamp.Editor.Controls;

public partial class EditorFrame : UserControl
{
    public Caret Caret { get; private set; }

    public EditorFrame()
    {
        InitializeComponent();
        Loaded += OnLoaded;
        PreviewKeyDown += OnKeyDown;
    }

    private void OnKeyDown(object sender, KeyEventArgs e)
    {
        if (DataContext is EditorFrameViewModel vm) {
            CursorPosition position = e.Key switch {
                Key.Right => new(0, 1),
                Key.Left => new(0, -1),
                Key.Up => new(-1, 0),
                Key.Down => new(1, 0),
                _ => new(0, 0)
            };
            if (vm.MoveCaretCommand.CanExecute(position)) {
                vm.MoveCaretCommand.Execute(position);
                e.Handled = true;
            }
        }
    }

    private void OnLoaded(object sender, RoutedEventArgs e)
    {
        Focus();
        AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(this);
        if (adornerLayer != null) {
            Caret = new Caret(this, 18);
            adornerLayer.Add(Caret);
        } else {
            System.Diagnostics.Debug.WriteLine("AdornerLayer still null. Check parent hierarchy.");
        }
        Loaded -= OnLoaded;
    }

    private Point CalculateCaretPosition(int line, int index, double scrollY, double scrollX)
    {
        return new Point(10 * index + scrollX, line * 18 + scrollY);
    }

    private void MoveCaret(Point point)
    {
        Caret?.UpdatePosition(point);
    }

    private void UpdateCaret()
    {
        int line = CursorPosition.Line;
        int charIndex = CursorPosition.Column;

        double scrollY = ScrollView.VerticalOffset;
        double scrollX = ScrollView.HorizontalOffset;

        MoveCaret(
            CalculateCaretPosition(
                line,
                charIndex,
                scrollY,
                scrollX));
    }

    public CursorPosition CursorPosition {
        get => (CursorPosition)GetValue(CursorPositionProperty);
        set => SetValue(CursorPositionProperty, value);
    }

    public static readonly DependencyProperty CursorPositionProperty =
        DependencyProperty.Register(
            nameof(CursorPosition), 
            typeof(CursorPosition), 
            typeof(EditorFrame), 
            new PropertyMetadata(CursorPosition.Void, OnCursorPositionChanged));

    private static void OnCursorPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var frame = (EditorFrame)d;
        frame.UpdateCaret();
    }
}