从两个抽象类继承，其中一个还需要另一个基类的部分

Question

This is more of a theoretical question without actual code example and I'm not sure if I am just overthinking this.

The whole thing is part of a GUI implemenation I am working on, where the GUI is represented as a tree structure consisting of Leafs and Nodes specializations which then have some special behavior like text content, an image or whatever which gets handled in its specific render() implementation.
However, my problem here is, that i would like to have a Hover functionality on some GUIs but that Hover functionality needs !some! of the basic GUI element functions, shown in the diagram, and now I can't wrap my head around how i connect these two parts into the final Button class. It has to inherit all the Leaf functionality plus the abstract Hover stuff.

Is there a way to make this work the way I am imagining it? Or do i have to give this Hover functionality to all GUIs and just implement a blank onMouseEnter() and onMouseExit() for the ones that don't use it?
The reason I would like to not give it to all GUIs is because the check if the mouse is hovering over the element is not for free. And not all elements have to be interactive.

A few notes:
- Hover might also be inherited by a Node specialization
- The list of functions in Hover is complete
- Leaf and Node both implement some of the abstract functions from Element in different ways

If you can come up with a better title for this, feel free to suggest an edit

Answer 1

I would extract the common functionalities of Element and Hover into a common base class:

           MouseBase
               |
 ------------------------------
 |                            |
 |                          Element
 |                            |
Hover                         |
 |             -------------------------------
 |             |                             |
 |            Leaf                          Node
 ---------------
        |
      Button

In that case, if MouseBase is a virtual base class, Button will get one single version of it, else it will have one via Element inheritance and a second one via Hover inheritance.