Why when I blit to a mem dc or a mem bmp, and then blit the mem dc to the screen...

[aewarnick]

Nothing at all:

HBITMAP hOldMemBmp= (HBITMAP)::SelectObject(imageDC, hBmp);

::StretchBlt(a::hdcMem, 0, 0, 800, 600, imageDC, 0, 0, BmpW, BmpH, SRCCOPY);

::BitBlt(hDC, invalLocation->left, invalLocation->top,
        invalLocation->right-invalLocation->left,
        invalLocation->bottom-invalLocation->top, a::hdcMem, 0, 0, SRCCOPY);

Black screen:

HBITMAP hOldMemBmp= (HBITMAP)::SelectObject(imageDC, hBmp);

::StretchBlt(hMemBmp, 0, 0, 800, 600, imageDC, 0, 0, BmpW, BmpH, SRCCOPY);

a::hOldBmp= (HBITMAP)::SelectObject(a::hdcMem, hMemBmp);

::BitBlt(hDC, invalLocation->left, invalLocation->top,
        invalLocation->right-invalLocation->left,
        invalLocation->bottom-invalLocation->top, a::hdcMem, 0, 0, SRCCOPY);