GetDC(null) sanity check...Will this DC ever get released?

[2kaud]

Is calling GetDC() as the parameter to a method like this good practice?

No. See Victor's post #2.

Should something different be done here?

For every GetDC() used, there must be a corresponding ReleaseDC() as per the MSDN documentation. See https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx re ReleaseDC().

Often you'll find code that at the start of a function/block obtains a DC with GetDC() and then at the end of the function/block calls ReleaseDC(). Note that ReleaseDC() requires both the DC handle and the windows handle. Note that even in the case of errors occurring from tested API return values, once GetDC() has been called, then ReleaseDC() still needs to be called. If you're using c++, then a RAII class can be used to obtain a DC and to ensure that ReleaseDC() is always called correctly.

PS Is GetDC() as used in the code in post #1 defined in the program elsewhere - as the standard Windows GetDC() takes a parameter of type HWND?

For a simple c++ class for DC, consider

class MyDC
{
public:
	MyDC(HWND win) : hwnd(win), dc(::GetDC(win)) {}

	~MyDC()
	{
		::ReleaseDC(hwnd, dc);
	}

	MyDC(const MyDC&) = delete;
	MyDC& operator=(const MyDC&) = delete;

	HDC GetDC() const 
	{
		return dc;
	}

private:
	HDC dc;
	HWND hwnd;
};

and useage

...
MyDC mydc(hwnd);
...
m_hOldBmp = (HBITMAP) ::SelectObject(mydc.GetDC(), m_hBmp);
...