struct FolderDisplay : public Display {
	virtual void Paint(Draw& w, const Rect& r, const Value& q, Color ink, Color paper, dword style) const;
};

struct FolderDisplay : public Display {
	void Paint(DisplayPaintCtx& ctx) const override {
            // ctx.GetDraw() or ctx.draw...
            // ctx.GetRect() or ctx.rect...
            // ctx.GetValue() or ctx.value... (v is too general for an outsider)
            // etc...
            // You do not need to extract all values for example style is not used in 90% of cases.
        }

        // The above method is super easy to override, the same as overriding Draw method in Ctrl...
};