怎么了！！！？？？走怎么了，这么简单的问题难不到你们才对。不需要看代码，说说而已

[attackboy]

有如下代码:
HBITMAP CButtonST::CreateBitmapMask(HBITMAP hSourceBitmap, DWORD dwWidth, DWORD dwHeight, COLORREF crTransColor)
{
HBITMAP hMask = NULL;
HDC hdcSrc = NULL;
HDC hdcDest = NULL;
HBITMAP hbmSrcT = NULL;
HBITMAP hbmDestT = NULL;
COLORREF crSaveBk;
COLORREF crSaveDestText;

hMask = ::CreateBitmap(dwWidth, dwHeight, 1, 1, NULL);
if (hMask == NULL) return NULL;

hdcSrc = ::CreateCompatibleDC(NULL);
hdcDest = ::CreateCompatibleDC(NULL);

hbmSrcT = (HBITMAP)::SelectObject(hdcSrc, hSourceBitmap);
hbmDestT = (HBITMAP)::SelectObject(hdcDest, hMask);

crSaveBk = ::SetBkColor(hdcSrc, crTransColor);

::BitBlt(hdcDest, 0, 0, dwWidth, dwHeight, hdcSrc, 0, 0, SRCCOPY);

crSaveDestText = ::SetTextColor(hdcSrc, RGB(255, 255, 255));
::SetBkColor(hdcSrc,RGB(0, 0, 0));

::BitBlt(hdcSrc, 0, 0, dwWidth, dwHeight, hdcDest, 0, 0, SRCAND);

SetTextColor(hdcDest, crSaveDestText);

::SetBkColor(hdcSrc, crSaveBk);
::SelectObject(hdcSrc, hbmSrcT);
::SelectObject(hdcDest, hbmDestT);

::DeleteDC(hdcSrc);
::DeleteDC(hdcDest);

return hMask;
}
我想问问:
返回的hMask句柄中,它在创建是被选进hdcDest中的,执行操作后应该是联系到返回位图hdcDest的,但后面的hdcSrc有什么关系呢?

[attackboy]

any one can help me?