Question

This is a bit tricky to explain but I will try my best to explain it.

I’m making a Gui API for games and it has Themes.

First I’ll explain how Widgets work.

A Button for example, inherits from Widget.
Themes work similarly.

ButtonTheme inherits from WidgetTheme.

Inside each widget class, there is an instance of its corrosponding Theme.

Widget class has:

    private:
   static WidgetTheme widgetTheme;
    public:
   static WidgetTheme& getWidgetTheme();

button class has:

  private:
    static ButtonTheme buttonTheme;
    public:
   static ButtonTheme& getButtonTheme();

the Widget constructor, builds itself from its theme ex:

Widget()
{
   setFont(getWidgetTheme().getFont());
}

the Button, inheriting from WidgetTheme, has to do the same ones because the internal widget will not know to construct from ButtonTheme, so my button ends up having to do:

Button()
{
   setFont(getButtonTheme().getFont());
   setButtonPadding(getButtonTheme().getButtonPadding());
}

This is where my problem is. It really feels wrong that I have to reprovide all the WidgetTheme ones and redirect them to ButtonTheme’s parameters for Widget. If I do not do this, a SuperButton would inherit the styles of Button which would also inherit the styles of Widget, but what I want is for SuperButton to use its version of ButtonTheme and WidgetTheme because SuperButtonTheme would inherit from ButtonTheme and WidgetTheme.

Is there a way I could redesign this so that the constructor only has to set parts of the theme that it brings, and not have to set those of its parents?

Thanks

Answer 1

A virtual getTheme() (as drewish suggests) but using covariant return types ought to solve your problem without requiring casts.