theme.go
func RealColor(clr term.Attribute, style string, id string) term.Attribute {
	var prefix string

	if style != "" {
		prefix = fmt.Sprintf("%s.", style)
	}

	ccolor := fmt.Sprintf("%s%s", prefix, id)

	if clr == ColorDefault {
		clr = SysColor(ccolor)
	}

	if clr == ColorDefault {
		panic("Failed to load color value for " + ccolor)
	}

	return clr
}
func RealColor(clr term.Attribute, style string, id string) term.Attribute {
	var prefix string

	if style != "" {
		prefix = fmt.Sprintf("%s.", style)
	}

	ccolor := fmt.Sprintf("%s%s", prefix, id)

	if clr == ColorDefault {
		clr = SysColor(ccolor)
	}

	if clr == ColorDefault {
		panic("Failed to load color value for " + ccolor)
	}

	return clr
}
// RealColor returns attribute that should be applied to an
// object. By default all attributes equal ColorDefault and
// the real color should be retrieved from the current theme.
// Attribute selection work this way: if color is not ColorDefault,
// it is returned as is, otherwise the function tries to load
// color from the theme.
//
// With the style argument themes may be grouped by control, i.e
// an application may have multiple list controls where they all share
// the same theme attributes however the same application may have
// one specific list control with some different theme attributes,
// in that case the user may call control.SetStyle("custom") and define
// a set of custom.* attributes, i.e:
//
//   custom.EditBox  = white
//   custom.EditText = black bold
//   ...
//
// clr - current object color
// style - the theme prefix style set
// id - color ID in theme