wartank/vendor/github.com/AllenDang/giu/Layout.go

package giu

const (
	// Auto is used to widget.Size to indicate height or width to occupy available spaces.
	Auto float32 = -1
)

// Widget is a base unit of giu rendering system.
// each widget just needs to implement Build method which is called,
// when widget needs to be rendered.
type Widget interface {
	Build()
}

var (
	_ Widget    = Layout{}
	_ Splitable = Layout{}
)

// Layout is a set of widgets. It implements Widget interface so
// Layout can be used as a widget.
type Layout []Widget

// Build implements Widget interface.
func (l Layout) Build() {
	for _, w := range l {
		if w != nil {
			w.Build()
		}
	}
}

// Splitable is implemented by widgets, which can be split (ranged)
// Layout implements Splitable.
type Splitable interface {
	Range(func(w Widget))
}

// Range ranges ofer the Layout, calling rangeFunc
// on each loop iteration.
func (l Layout) Range(rangeFunc func(Widget)) {
	for _, w := range l {
		if splitable, canRange := w.(Splitable); canRange {
			splitable.Range(rangeFunc)
			continue
		}

		rangeFunc(w)
	}
}