如何在App B中创建窗口，以便App A可以使用它来呈现而不是使用自己的Window

Question

Folks, I apologize if this sounds like a newbie questions, but I am not very familiar with Windows development as a whole. So I was given App A, which does a lot of things and one particular function is to render a duck picture. Internally it created the Window with the title 'DrawingBoard' and later on when the program is ready to render it will try to find this "DrawingBoard" window. I was only told that this is how App A finds the window to render the duck:

     static const TCHAR TITLE_NAME[] = "DrawingBoardParent";   
     static const TCHAR TITLE_CLASS_NAME[] = "DrawingBoard";

     HWND parent = FindWindowExA(NULL, NULL, NULL, TITLE_NAME);
     while (parent != NULL)
     {
        //find the child window by window title
        window = findWindowRecursive(parent, TITLE_CLASS_NAME);
        if (window != NULL)
        {
           break;
        }
        //no child by the given title name found, go down one level
        parent = FindWindowExA(NULL, parent, NULL, TITLE_NAME);
     }

Now I need to create App B and I want to create my own "DrawingBoard" window on App B. Because App A uses the above algorithm to find the rendering window, instead of using it's own App A "DrawingBoard" Window, it will use my App B "DrawingBoard" Window.

Questions:

1) Is this within the realm of possibility at all ? 2) Say if both App A & B have two windows with the same title "DrawingBoard". Which one does FindWindowEx(NULL, NULL, NULL, ""DrawingBoard"); return ? 3) If FindWindowEx always returns the handle for App A "DrawingBoard" window. How do I hack it so it will return App B "DrawingBoard" window.

Thanks for the help folks.

Answer 1

Say if both App A & B have two windows with the same title "DrawingBoard" . Which one does FindWindowEx(NULL, NULL, NULL, ""DrawingBoard") return?

That is ill-defined. It will return one of them. You cannot influence which is returned.

If FindWindowEx always returns the handle for App A "DrawingBoard" window. How do I hack it so it will return App B "DrawingBoard" window.

You cannot. The other app is broken. Its search for a window that it created is broken, since it can yield the wrong window, a window from another process.

You can avoid getting caught out by this app by using a different name for your window. However you really ought to either fix or remove the defective program. That's the sane way forward.