Is OnPaint just a MFC function?

I have my window subclassed and was hoping that instead of completely overriding every message that I handle, it would carry out whatever is in the subclassed window as well, like C# does in the OnPaint event.

In C# I have a choice whether to completely override it or not and when it is carried out using
base.OnPaint(e);

I hope you know what I mean. How would I do this?

<base class name>::OnPaint(bla);

And yeah, OnPaint is not there in WinAPI, although no one prevents you from declaring one ;)

In the WinAPI, when you're subclassing, you receive the old WNDPROC pointer. You need to store it and in the subclassing WndProc, instead of calling DefWindowProc, call
return CallWindowProc(pOldWndProc, hwnd, msg, wparam, lparam);

Yes I have done that in my sub classed window. The problem is that it does not call the messages that I handled, only the ones I didn't. In C# I can call the base class to do it's work and then paint over it. But that can slow. I guess that is not a good concept for C++.

It depends.

You're right, I guess it depends upon how I implement everything. What I could do is make my own OnPaint function and pass the window message to it including a rectangle of the area I want erased or refreshed, draw that to a memory HDC, pass the memory HDC back and draw to that.

Good thinking CornedBee.