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

namespace DragControlDemo
{
    public partial class MainForm : Form
    {
        private Point _dragOffset;
        private bool _isDragging = false;
        private Control _currentDragControl;

        public MainForm()
        {
            InitializeComponent();
            SetupDraggableControls();
        }

        private void SetupDraggableControls()
        {
            // 創(chuàng)建多個(gè)可拖動(dòng)的標(biāo)簽控件
            for (int i = 0; i < 4; i++)
            {
                var label = new Label
                {
                    Text = $"可拖動(dòng)標(biāo)簽 {i + 1}",
                    BackColor = Color.LightBlue,
                    AutoSize = false,
                    Size = new Size(120, 40),
                    Location = new Point(50 + i * 30, 50 + i * 40),
                    TextAlign = ContentAlignment.MiddleCenter,
                    BorderStyle = BorderStyle.FixedSingle
                };

                // 綁定事件處理器
                label.MouseDown += Control_MouseDown;
                label.MouseMove += Control_MouseMove;
                label.MouseUp += Control_MouseUp;
                
                this.Controls.Add(label);
            }
        }

        private void Control_MouseDown(object sender, MouseEventArgs e)
        {
            // 僅響應(yīng)左鍵拖動(dòng)
            if (e.Button != MouseButtons.Left) return;
            
            var control = sender as Control;
            _currentDragControl = control;
            
            // 計(jì)算鼠標(biāo)相對(duì)于控件左上角的偏移量
            _dragOffset = new Point(e.X, e.Y);
            _isDragging = true;
            
            // 啟用鼠標(biāo)捕獲，確保鼠標(biāo)移出控件范圍仍能接收事件
            control.Capture = true;
            
            // 可選：改變控件外觀提示拖動(dòng)狀態(tài)
            control.BackColor = Color.LightCoral;
        }

        private void Control_MouseMove(object sender, MouseEventArgs e)
        {
            // 檢查是否處于拖動(dòng)狀態(tài)
            if (!_isDragging || _currentDragControl == null) return;
            
            // 暫停布局更新以提升性能
            this.SuspendLayout();
            
            // 坐標(biāo)轉(zhuǎn)換：從控件坐標(biāo) → 屏幕坐標(biāo) → 父容器坐標(biāo)
            var screenPoint = _currentDragControl.PointToScreen(new Point(e.X, e.Y));
            var parentClientPoint = this.PointToClient(screenPoint);
            
            // 應(yīng)用偏移量修正，保持鼠標(biāo)與控件的相對(duì)位置不變
            var newLocation = new Point(
                parentClientPoint.X - _dragOffset.X,
                parentClientPoint.Y - _dragOffset.Y
            );
            
            // 更新控件位置
            _currentDragControl.Location = newLocation;
            
            // 恢復(fù)布局更新
            this.ResumeLayout();
        }

        private void Control_MouseUp(object sender, MouseEventArgs e)
        {
            if (_isDragging && e.Button == MouseButtons.Left)
            {
                _isDragging = false;
                
                if (_currentDragControl != null)
                {
                    // 釋放鼠標(biāo)捕獲
                    _currentDragControl.Capture = false;
                    
                    // 恢復(fù)控件原始外觀
                    _currentDragControl.BackColor = Color.LightBlue;
                    
                    _currentDragControl = null;
                }
            }
        }
    }
}

// 詳細(xì)坐標(biāo)轉(zhuǎn)換流程
private Point CalculateNewLocation(Control control, Point mousePos)
{
    // 步驟1：獲取控件在當(dāng)前鼠標(biāo)位置的屏幕坐標(biāo)
    Point screenPoint = control.PointToScreen(mousePos);
    
    // 步驟2：將屏幕坐標(biāo)轉(zhuǎn)換為父容器的客戶區(qū)坐標(biāo)
    Point parentPoint = control.Parent.PointToClient(screenPoint);
    
    // 步驟3：應(yīng)用初始偏移量，防止控件跳轉(zhuǎn)到鼠標(biāo)中心
    return new Point(
        parentPoint.X - _dragOffset.X,
        parentPoint.Y - _dragOffset.Y
    );
}

private void OptimizedMouseMove(object sender, MouseEventArgs e)
{
    if (!_isDragging) return;
    
    try
    {
        this.SuspendLayout(); // 暫停布局計(jì)算
        
        // 執(zhí)行位置更新邏輯
        var newLoc = CalculateNewLocation(_currentDragControl, new Point(e.X, e.Y));
        _currentDragControl.Location = newLoc;
    }
    finally
    {
        this.ResumeLayout(); // 恢復(fù)布局計(jì)算
    }
}

public class DragManager
{
    private Point _dragStartPoint;
    private bool _isDragging = false;
    private Control _dragTarget;
    
    public void EnableDrag(Control control)
    {
        control.MouseDown += (s, e) =>
        {
            if (e.Button == MouseButtons.Left)
            {
                _dragTarget = control;
                _dragStartPoint = new Point(e.X, e.Y);
                _isDragging = true;
                control.Capture = true;
            }
        };
        
        control.MouseMove += (s, e) =>
        {
            if (_isDragging && _dragTarget != null)
            {
                var parent = _dragTarget.Parent;
                parent.SuspendLayout();
                
                var screenPoint = _dragTarget.PointToScreen(new Point(e.X, e.Y));
                var parentPoint = parent.PointToClient(screenPoint);
                
                _dragTarget.Location = new Point(
                    parentPoint.X - _dragStartPoint.X,
                    parentPoint.Y - _dragStartPoint.Y
                );
                
                parent.ResumeLayout();
            }
        };
        
        control.MouseUp += (s, e) =>
        {
            if (e.Button == MouseButtons.Left)
            {
                _isDragging = false;
                if (_dragTarget != null)
                {
                    _dragTarget.Capture = false;
                    _dragTarget = null;
                }
            }
        };
    }
}

// 使用示例
var dragManager = new DragManager();
dragManager.EnableDrag(myButton);
dragManager.EnableDrag(myPanel);

private DockStyle _savedDock;
private AnchorStyles _savedAnchor;

private void PrepareForDrag(Control control)
{
    _savedDock = control.Dock;
    _savedAnchor = control.Anchor;
    
    control.Dock = DockStyle.None;
    control.Anchor = AnchorStyles.None;
}

private void RestoreAfterDrag(Control control)
{
    control.Dock = _savedDock;
    control.Anchor = _savedAnchor;
}