In any event, nice blog! Steve pointed it out to me, in case you’re wondering where I came from.

The reason I want to do it this way, is because 95% of the code for my control class is the same. It’s mainly one method which reads the dialog control info from a file - the text, color, font, position, etc. So all of that code fits nicely in my base class, and from the outside I just need to call a generic LoadFromFile method, and the class does everything. The descendant classes can override this method to add any special items, like a flag for a checkbox for instance.

There are some other basic methods, like adding a bitmap, which one control might handle differently than another.

My solution to use GetCWnd() method to get the class ptr I need is not so bad. The thing I’m more unhappy about is not being able to implement message handlers such as CtlColor and OnSetCursor in the base class. If I’ve got 5 control classes, now I have 5 copies of the same handlers. I loathe redundant code, it keeps me up at night.

http://msdn2.microsoft.com/en-us/library/wcz57btd(VS.80).aspx

I finally think I understand what you’re after now though. You have a bunch of CWnd controls (like CEdit, CButton, etc), but you also want them to inherit from your common set of “Control” functionality. But your Control functionality wants to be a CWnd as well so it can manipulate the control as a base window object. However, you can’t make Control inherit from CWnd because of multiple vtables. Basically correct?

My classes are simple:

class CMyControl : virtual public CWnd {…}

class CMyEdit : public CEdit, public CMyControl {…}

The class that uses CMyControl (a dialog class, go figure) doesn’t need to know if it’s an edit control, or a checkbox control, or what. It just needs to know that it’s a “contorl” and it can go ahead and position it, or set its font, or change its color, etc. The descendant classes to CMyControl - like CMyEdit - will implement those functions. I don’t need to worry about it, because the underlying MFC controls already do those things. But, if I’m the dialog class and all I have is a pointer to CMyControl, then I need to get a hold of a pointer to the CWnd object to do those things.

Also, I don’t think you’re last statement is correct. Delcaring a pure virtual base class (I believe) is just like declaring a virtual method in a base class. Once you’ve done it, the descendants are automatically virtual whether you use the keyword or not.