PKHeX/PKHeX.WinForms/Controls/Slots/DragManager.cs

using System;
using System.Drawing;
using System.Windows.Forms;

namespace PKHeX.WinForms.Controls;

/// <summary>
/// Manages drag-and-drop operations for slot controls.
/// </summary>
public sealed class DragManager : IDisposable
{
    /// <summary>
    /// Gets the current slot change information for drag-and-drop operations.
    /// </summary>
    public SlotChangeInfo<Cursor, PictureBox> Info { get; private set; } = new();

    /// <summary>
    /// Occurs when an external drag-and-drop operation is requested.
    /// </summary>
    public event DragEventHandler? RequestExternalDragDrop;
    private BitmapCursor? OwnedCursor;

    /// <summary>
    /// Requests a drag-and-drop operation.
    /// </summary>
    /// <param name="sender">The sender of the event.</param>
    /// <param name="e">The drag event arguments.</param>
    public void RequestDD(object sender, DragEventArgs e) => RequestExternalDragDrop?.Invoke(sender, e);

    /// <summary>
    /// Sets the cursor for the specified form and updates the drag info.
    /// </summary>
    /// <param name="f">The form to set the cursor for.</param>
    /// <param name="z">The cursor to set.</param>
    public void SetCursor(Control f, Cursor? z)
    {
        if (OwnedCursor is not null && !ReferenceEquals(OwnedCursor.Cursor, z))
            DisposeOwnedCursor();
        f.Cursor = z;
        Info.Cursor = z;
    }

    public void SetOwnedCursor(Control f, Bitmap bitmap)
    {
        DisposeOwnedCursor();
        OwnedCursor = new BitmapCursor(bitmap);
        SetCursor(f, OwnedCursor.Cursor);
    }

    /// <summary>
    /// Resets the cursor for the specified form to the default cursor.
    /// </summary>
    /// <param name="sender">The form to reset the cursor for.</param>
    public void ResetCursor(Control sender)
    {
        SetCursor(sender, Cursors.Default);
    }

    /// <summary>
    /// Initializes the drag manager and resets the drag info.
    /// </summary>
    public void Initialize()
    {
        DisposeOwnedCursor();
        Info = new SlotChangeInfo<Cursor, PictureBox>();
    }

    /// <summary>
    /// Resets the drag manager's slot change info.
    /// </summary>
    public void Reset()
    {
        DisposeOwnedCursor();
        Info.Reset();
    }

    private void DisposeOwnedCursor()
    {
        if (OwnedCursor is null)
            return;
        OwnedCursor.Dispose();
        OwnedCursor = null;
    }

    public void Dispose() => DisposeOwnedCursor();

    /// <summary>
    /// Gets or sets the mouse down position for drag detection.
    /// </summary>
    public Point MouseDownPosition { private get; set; }

    /// <summary>
    /// Gets a value indicating whether a drag operation can be started.
    /// </summary>
    public bool CanStartDrag => Info.IsLeftMouseDown && !Cursor.Position.Equals(MouseDownPosition);
}