CryptoProfile-Tracker/CryptoPortfolio Tracker/Behaviors/WindowsDragBehavior.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.VisualTree;

namespace CryptoPortfolio_Tracker.Behaviors;

public static class WindowDragBehavior
{
    public static readonly AttachedProperty<bool> EnableWindowDragProperty =
        AvaloniaProperty.RegisterAttached<Control, bool>(
            "EnableWindowDrag",
            typeof(WindowDragBehavior));

    public static bool GetEnableWindowDrag(Control element) =>
        element.GetValue(EnableWindowDragProperty);

    public static void SetEnableWindowDrag(Control element, bool value) =>
        element.SetValue(EnableWindowDragProperty, value);

    static WindowDragBehavior()
    {
        EnableWindowDragProperty.Changed.AddClassHandler<Control>(OnEnableWindowDragChanged);
    }

    private static void OnEnableWindowDragChanged(Control control, AvaloniaPropertyChangedEventArgs e)
    {
        if (e.NewValue is true)
        {
            // Контрол ещё может не быть в визуальном дереве
            if (control.IsLoaded)
                Attach(control);
            else
                control.Loaded += OnControlLoaded;
        }
        else
        {
            control.Loaded -= OnControlLoaded;
            Detach(control);
        }
    }

    private static void OnControlLoaded(object? sender, RoutedEventArgs e)
    {
        if (sender is Control control)
        {
            control.Loaded -= OnControlLoaded;
            Attach(control);
        }
    }

    private static void Attach(Control control)
    {
        var topBar = FindInVisualTree<Border>(control, "PART_NavigationBar");
        if (topBar is null)
            return;

        topBar.AddHandler(
            InputElement.PointerPressedEvent,
            OnTopBarPointerPressed,
            RoutingStrategies.Tunnel);
    }

    private static void Detach(Control control)
    {
        var topBar = FindInVisualTree<Border>(control, "Border#PART_NavigationBar");
        if (topBar is null)
            return;

        topBar.RemoveHandler(
            InputElement.PointerPressedEvent,
            OnTopBarPointerPressed);
    }

    private static void OnTopBarPointerPressed(object? sender, PointerPressedEventArgs e)
    {
        if (!e.GetCurrentPoint(null).Properties.IsLeftButtonPressed)
            return;

        // Проверяем — нажатие было на кнопке или интерактивном элементе?
        if (e.Source is Visual source && IsInteractiveElement(source))
            return;

        if (sender is Visual visual &&
            TopLevel.GetTopLevel(visual) is Window window)
        {
            window.BeginMoveDrag(e);
        }
    }
    
    private static bool IsInteractiveElement(Visual visual)
    {
        Visual? current = visual;
        while (current is not null)
        {
            if (current is Button or ToggleButton or CheckBox or 
                RadioButton or Slider or TextBox or ComboBox)
                return true;

            if (current is Border { Name: "Border#PART_NavigationBar" })
                break;

            current = current.GetVisualParent();
        }
        return false;
    }

    private static T? FindInVisualTree<T>(Visual root, string name) where T : Visual
    {
        if (root is T typed && root.Name == name)
            return typed;

        foreach (var child in root.GetVisualChildren())
        {
            var result = FindInVisualTree<T>(child, name);
            if (result is not null)
                return result;
        }

        return null;
    }
}