DWM缩略图，更改预览窗口的大小

Question

我有窗口，它用DWM缩略图镜像另一个窗口。现在我希望当用户调整预览窗口大小时，比调整预览区域大小。我怎样才能做到这一点？如何发送有关新预览大小的更新（将大小300x300更改为预览窗口的大小）？

switch (message) {
case WM_CREATE:
    {
        HRESULT hr = S_OK;
        HTHUMBNAIL thumbnail = NULL;
        hr = DwmRegisterThumbnail(hWnd, ieWindowHwnd, &thumbnail);
        if (SUCCEEDED(hr)) {
            // The destination rectangle size
            RECT dest = {0,0,300,300};

            // Set the thumbnail properties for use
            DWM_THUMBNAIL_PROPERTIES dskThumbProps;
            dskThumbProps.dwFlags = DWM_TNP_RECTDESTINATION | DWM_TNP_VISIBLE | DWM_TNP_SOURCECLIENTAREAONLY;

            // Use the window frame and client area
            dskThumbProps.fSourceClientAreaOnly = FALSE;
            dskThumbProps.fVisible = TRUE;
            dskThumbProps.rcDestination = dest;

            // Display the thumbnail
            hr = DwmUpdateThumbnailProperties(thumbnail, &dskThumbProps);
        }
    }
    break;
case WM_SIZE:
    {
        // What to do here.
    }
    break;