How to obtain the real-time properties of a custom title bar in C++/WinRT WinUI3

Question

1. What I get from m_mainWindow.MyBut().ActualOffset() or m_mainWindow.MyBut().TransformToVisual() is 0. The value of the coordinate attribute will only change when the window changes.
2. I tried the link that has properties that may provide coordinates https://learn.microsoft.com/zh-cn/uwp/api/windows.ui.xaml.controls.button?view=winrt-22621
3. How do I get the coordinates of this element? I saw an example in C# that can get the coordinates like this. I don’t know if it’s a problem with C++/WinRT WinUI.

#include "pch.h"
#include "TitlebarPage.xaml.h"
#if __has_include("TitlebarPage.g.cpp")
#include "TitlebarPage.g.cpp"
#endif

using namespace winrt;
using namespace Windows::UI;
using namespace Microsoft::UI::Xaml;
using namespace Microsoft::UI::Xaml::Controls;
using namespace Microsoft::UI::Xaml::Navigation;
using namespace Microsoft::UI::Input;


namespace winrt::SampleApp::implementation
{

    winrt::hstring defaultTitle = L"WinUI C++ Desktop sample App";

    TitlebarPage::TitlebarPage()
    {
        InitializeComponent();
        TitlebarCustomBtn().PointerPressed({this, 
        &TitlebarPage::TitlebarCustomBtn_Click});
        TitlebarCustomBtn().PointerPressed({ this, 
        &TitlebarPage::TitlebarCustomBtn_Click });
    }
  
    void TitlebarPage::OnNavigatedTo(NavigationEventArgs const& e)
    {
            m_mainWindow = e.Parameter().as<MainWindow>();
            
            AppWindow appWindow = m_mainWindow.MyAppWindow();
            m_appWindow = appWindow;
            m_changedToken = m_appWindow.Changed({ this, 
            &TitlebarPage::AppWindowChangedHandler });          
    }

    void TitlebarPage::AppWindowChangedHandler(winrt::Windows::Foundation::IInspectable 
    const& sender, winrt::Microsoft::UI::Windowing::AppWindowChangedEventArgs const& e)
    {
        if (e.DidSizeChange() 
         && sender.as<AppWindow>().TitleBar().ExtendsContentIntoTitleBar())
        {
            SetCustomTitleBarDragRegion();
        }
    }

    void TitlebarPage::TitlebarBrandingBtn_Click(
    winrt::Windows::Foundation::IInspectable const& /*sender*/, 
    winrt::Microsoft::UI::Xaml::RoutedEventArgs const& /*e*/)
    {
        m_appWindow.TitleBar().ResetToDefault();
        m_mainWindow.MyTitleBar().
        Visibility(winrt::Microsoft::UI::Xaml::Visibility::Collapsed);

        m_brandTitleBar = !m_brandTitleBar;
   
        if (AppWindowTitleBar::IsCustomizationSupported() && m_brandTitleBar)
        {
            m_appWindow.Title(L"Default titlebar with custom color customization");
            m_appWindow.TitleBar().ForegroundColor(Colors::Transparent());
            m_appWindow.TitleBar().BackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().InactiveBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().InactiveForegroundColor(Colors::Transparent());

            //Buttons
            m_appWindow.TitleBar().ButtonBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonForegroundColor(Colors::Transparent());
            m_appWindow.TitleBar().
            ButtonInactiveBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().
            ButtonInactiveForegroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonHoverBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonHoverForegroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonPressedBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonPressedForegroundColor(Colors::Transparent());   
        }
        else
        {
            m_appWindow.TitleBar().ResetToDefault();
            m_appWindow.Title(defaultTitle);
        }
    }

    void TitlebarPage::TitlebarCustomBtn_Click(winrt::Windows::Foundation::IInspectable 
     const& /*sender*/, winrt::Microsoft::UI::Xaml::RoutedEventArgs const& /*e*/)
    {

        if (AppWindowTitleBar::IsCustomizationSupported() && !m_customTitleBar) {
            m_customTitleBar = true;
            m_appWindow.TitleBar().ExtendsContentIntoTitleBar(true);

            // Show the custom titlebar
            m_mainWindow.MyTitleBar().
            Visibility(winrt::Microsoft::UI::Xaml::Visibility::Visible);

            // Set Button colors to match the custom titlebar
            m_appWindow.TitleBar().ButtonBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonForegroundColor(Colors::Gray());
            m_appWindow.TitleBar().
            ButtonInactiveBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonInactiveForegroundColor(Colors::Gray());
            m_appWindow.TitleBar().ButtonHoverBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonHoverForegroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonPressedBackgroundColor(Colors::Transparent());
            m_appWindow.TitleBar().ButtonPressedForegroundColor(Colors::Gray());               
            m_appWindow.TitleBar().
            IconShowOptions(IconShowOptions::HideIconAndSystemMenu);
            //Set the drag region for the custom titlebar
            SetCustomTitleBarDragRegion();
        }
        else
        {
            // Bring back the default titlebar
            m_customTitleBar = false;
        m_mainWindow.MyTitleBar().
        Visibility(winrt::Microsoft::UI::Xaml::Visibility::Collapsed);
            m_appWindow.TitleBar().ResetToDefault();
        }
    }

    void TitlebarPage::ResetTitlebarBtn_Click(winrt::Windows::Foundation::IInspectable 
    const& /*sender*/, winrt::Microsoft::UI::Xaml::RoutedEventArgs const& /*e*/)
    {       
    m_mainWindow.MyTitleBar().Visibility(
    winrt::Microsoft::UI::Xaml::Visibility::Collapsed);
        m_appWindow.TitleBar().ResetToDefault();
        m_appWindow.Title(defaultTitle);
    }

    void TitlebarPage::SetCustomTitleBarDragRegion()
    {

        double scaleAdjustment = 
        m_mainWindow.MyTitleBar().XamlRoot().RasterizationScale();
        double scaleAdjustment2 =m_mainWindow.MyBut().XamlRoot().RasterizationScale();

        GeneralTransform transform = m_mainWindow.MyBut().TransformToVisual(nullptr);
        
        static Rect bunds;
         bunds = transform.TransformBounds(Rect(0, 0, 
                                                m_mainWindow.MyBut().ActualWidth(), 
                                                m_mainWindow.MyBut().ActualHeight()));

        std::vector<Windows::Graphics::RectInt32> dragRects;
        Windows::Graphics::RectInt32 MyButRect;

        MyButRect.X = static_cast<int>(bunds.X * scaleAdjustment);
        MyButRect.Y = static_cast<int>(bunds.Y * scaleAdjustment);
        MyButRect.Height = static_cast<int>(bunds.Height * scaleAdjustment);
        MyButRect.Width = static_cast<int>(bunds.Width * scaleAdjustment);
        dragRects.push_back(MyButRect);

        InputNonClientPointerSource nonClientInputSrc = 
        InputNonClientPointerSource::GetForWindowId(m_appWindow.Id());
        nonClientInputSrc.SetRegionRects(NonClientRegionKind::Passthrough, dragRects);
    }
}