what's an operator HBRUSH??

[Bilal Naveed]

MFC Graphics classes like CBrush, CBitmap, etc. define a member "operator HBRUSH() const", or "operator HBITMAP() const". I thought that you couldn't define new operator types! Somebody explain what these are :confused: Bilal

[Christian Graus]

MFC GDI classes like CBrush, CDC and CBitmap are merely thin wrappers around Win32 functions. Everything that CDC, for example, does is really a wrapper around functions of the same name. So CDC::CreateCompatibleDC is a wrapper around a function called CreateCompatibleDC, which takes the same variables as CreateCompatibleDC ( a pointer to a DC or NULL), plus a HDC, which is a handle to a DC. A major benefit of this is that they are cleaned up by the destructor - not calling delete on a GDI resource in a Win32 program is a sure fire way to achieve memory leaks and disaster, MFC makes it a little harder to mess up. CDC as a class is then just a spot to hold a HDC and do HDC stuff to it. Any class can overload an operator in order to enable implicit casting to that type, for example a string class would overload char* so you could put an instance of the class where a char * is expected. The GDI classes have such an overload, so that anything that expects the handle can get it, although I usually point to the member variable ( such as m_hDC, m_hBitmap, etc. ) to be sure. Christian The content of this post is not necessarily the opinion of my yadda yadda yadda. To understand recursion, we must first understand recursion.

[Michael Dunn]

A class can define conversion functions, which is what those MFC functions are. For example, CBrush::operator HBRUSH() is called if you pass a CBrush to a function expecting an HBRUSH, or if you explicitly cast a CBrush to HBRUSH. You still use the keyword operator in the code. --Mike-- http://home.inreach.com/mdunn/ All your base are belong to ME~!