Using cdockablepane to realize floating window in MFC

Camera.h

#pragma once
#include "afxdialogex.h"
// Camera  Dialog box 
class Camera : public CDialogEx
{
    
	DECLARE_DYNAMIC(Camera)
public:
	Camera(CWnd* pParent = nullptr);   //  Standard constructors 
	virtual ~Camera();
//  Dialog data 
#ifdef AFX_DESIGN_TIME
	enum {
     IDD = IDD_CAMERA };
#endif
protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV  Support 
	DECLARE_MESSAGE_MAP()
public:
	afx_msg void OnBnClickedButton1();
};
class CCameraPane : public CDockablePane
{
    
public:
	CCameraPane();
	virtual ~CCameraPane();
private:
	Camera m_Camera;
protected:
	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
	afx_msg void OnSize(UINT nType, int cx, int cy);
	afx_msg void OnDestroy();

	DECLARE_MESSAGE_MAP()
};

Camera.cpp

// Camera.cpp:  Implementation file 
//
#include "pch.h"
#include "afxdialogex.h"
#include "Camera.h"
// Camera  Dialog box 
IMPLEMENT_DYNAMIC(Camera, CDialogEx)
//  Dialog data 
#ifdef AFX_DESIGN_TIME
enum {
     IDD = IDD_CAMERA };
#endif
Camera::Camera(CWnd* pParent /*=nullptr*/)
	: CDialogEx(IDD_CAMERA, pParent)
{
    
}
Camera::~Camera()
{
    
}
void Camera::DoDataExchange(CDataExchange* pDX)
{
    
	CDialogEx::DoDataExchange(pDX);
}
BEGIN_MESSAGE_MAP(Camera, CDialogEx)
	ON_BN_CLICKED(IDC_BUTTON1, &Camera::OnBnClickedButton1)
END_MESSAGE_MAP()
// Camera  Message handler 
void Camera::OnBnClickedButton1()
{
    
	// TODO:  Add control notification handler code here 
}
CCameraPane::CCameraPane()
{
    
}
CCameraPane::~CCameraPane()
{
    
}
void CCameraPane::OnDestroy()
{
    
	CDockablePane::OnDestroy();
	m_Camera.DestroyWindow();
}
/// <summary>
///  Subform suspension 
/// </summary>
/// <param name="lpCreateStruct"></param>
/// <returns></returns>
int CCameraPane::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    
	if (CDockablePane::OnCreate(lpCreateStruct) == -1)
		return -1;

	// TODO: Add your specialized creation code here 
	if (!m_Camera.Create(IDD_CAMERA, this))
	{
    
		TRACE0(" Failed to create window /n");
		return -1;
	}
	m_Camera.ShowWindow(SW_SHOW);
	return 0;
}
/// <summary>
///  Eliminate the residual shadow of the form 
/// </summary>
/// <param name="nType"></param>
/// <param name="cx"></param>
/// <param name="cy"></param>
void CCameraPane::OnSize(UINT nType, int cx, int cy)
{
    
	CDockablePane::OnSize(nType, cx, cy);
	if (m_Camera.GetSafeHwnd())
	{
    
		CRect rect;
		GetClientRect(rect);
		m_Camera.MoveWindow(rect);
	}
}
BEGIN_MESSAGE_MAP(CCameraPane, CDockablePane)
	ON_WM_CREATE()
	ON_WM_SIZE()
END_MESSAGE_MAP()

MainFrm.h

    CCameraPane		  m_wndCameraPane;

MainFrm.cpp

	//  Create test dialog 
	if (!m_wndCameraPane.Create(_T(" test "), this, CRect(0, 0, 200, 200), TRUE, IDD_CAMERA, WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | CBRS_LEFT | CBRS_FLOAT_MULTI))
	{
    
		TRACE0(" Failed to create window \n");
		return FALSE; //  Failed to create 
	}
	m_wndCameraPane.EnableDocking(CBRS_ALIGN_ANY);
	DockPane(&m_wndCameraPane);