c++ - DWM 缩略图，更改预览窗口的大小

Question

我有一个窗口，它反射(reflect)了另一个带有 DWM 缩略图的窗口。现在我想要当用户调整预览窗口大小时，预览区域会调整到。我怎样才能做到这一点？如何发送有关新预览尺寸的更新(将尺寸 300x300 更改为预览窗口的尺寸)？

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;

Answer 1

从WM_CREATE 中移除thumbnail 声明，在Window 过程中将其声明为静态值。然后更新 WM_SIZE 中的 thumbnail。

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wp, LPARAM lp)
{
    static HTHUMBNAIL thumbnail = NULL;

    switch (message)
    {
    ...    
    case WM_SIZE:
    {
        if (thumbnail)
        {
            RECT rc;
            GetClientRect(hWnd, &rc);
            DWM_THUMBNAIL_PROPERTIES dskThumbProps;
            ...
            dskThumbProps.rcDestination = rc;
            DwmUpdateThumbnailProperties(thumbnail, &dskThumbProps);
        }
        break;
    }
}

完成后调用 DwmUnregisterThumbnail。