C / C++ / MFC

void Init (CxImage *i)
{
    CWindowDC dcScreen (CWnd::FromHandle (::GetDesktopWindow ()));

    w = i->GetWidth();
    h = i->GetHeight();

    VERIFY(CreateCompatibleDC(&dcScreen));    // <-- Changed to make it more obvious.
    ////////////////////////////
    VERIFY(bmp.CreateCompatibleBitmap(&dcScreen, w, h)); // <-- Changed
    ////////////////////////////
    bmpOld = (CBitmap*)SelectObject(bmp);
    i->Draw(m_hDC); // Works if I do this on the window DC straight away
}

class CTilesetDC :<br />
	public CDC<br />
{<br />
	CBitmap bmp;<br />
	CBitmap *bmpOld;<br />
public:<br />
<br />
	Uint32 w, h;<br />
<br />
	CTilesetDC(CxImage *i, CDC *target)<br />
	{<br />
		w = i->GetWidth();<br />
		h = i->GetHeight();<br />
<br />
		VERIFY(CreateCompatibleDC(target));<br />
		VERIFY(bmp.CreateCompatibleBitmap(target, w, h));<br />
		bmpOld = (CBitmap*)SelectObject(bmp);<br />
		i->Draw(GetSafeHdc());<br />
	}<br />
<br />
	~CTilesetDC()<br />
	{<br />
		SelectObject(bmpOld);<br />
	}<br />
};

<br />
class CTestDC : public CDC<br />
{<br />
    ....<br />
    CBitmap    bmpOld;<br />
    ....<br />
<br />
    CTestDC (....)<br />
    {<br />
        ....<br />
        bmpOld.Attach (SelectObject (&bmpNew)->Detach ());<br />
        ....<br />
    }<br />
<br />
    ~CTestDC ()<br />
    {<br />
        SelectObject (&bmpOld);<br />
        bmpOld.Detach (); // <-- If you don't do this, then ~CBitmap will call DeleteObject, which we don't to be purist...<br />
    }<br />
}<br />