Function DropdownIndexFromPoint

src/openrct2-ui/windows/Dropdown.cpp:504–512

* New function based on 6e914e * returns -1 if index is invalid */

     * returns -1 if index is invalid
     */
    int32_t DropdownIndexFromPoint(const ScreenCoordsXY& loc, WindowBase* w)
    {
        if (w->classification == WindowClass::dropdown)
        {
            auto* ddWnd = static_cast<DropdownWindow*>(w);
            return ddWnd->GetIndexFromPoint(loc);
        }
        return -1;
    }

    // Colour ordered for use in colour dropdown
    static constexpr Colour kColoursDropdownOrder[] = {