[Missing] sysytem.CommandEvent missing

[diyism]

I'm always using sysytem.CommandEvent to control the "Back Button" behavior in android:

func loop(w *app.Window) error
{	th := material.NewTheme(gofont.Collection())
	var ops op.Ops
	var wv  gowebview.WebView
	for
	{	e:=<-w.Events()
		switch e:=e.(type)
		{	case app.ViewEvent:
				if wv==nil
				{	go func()
					{	var err error
						wv,err = gowebview.New(&gowebview.Config{URL:"https://google.com/ncr", WindowConfig:&gowebview.WindowConfig{Title:"Hello World", Window:e.View, VM:app.JavaVM()}})
						if err!=nil {panic(err)}
						defer wv.Destroy()
						wv.Run()
					}()
				}
			case *system.CommandEvent:
				if e.Type==system.CommandBack
				{	log.Println("===================back button hibernate==============", wv)
					e.Cancel = true
					//wv.SetVisibility(gowebview.VisibilityMinimized)
					go wv.Hibernate()
				}

I can see the system.CommandEvent and system.CommandBack in gioui.org/io/system/system.go(v0.0.0-20210817080256-3773daf155b4):

// CommandEvent is a system event. Unlike most other events, CommandEvent is
// delivered as a pointer to allow Cancel to suppress it.
type CommandEvent struct {
	Type CommandType
	// Cancel suppress the default action of the command.
	Cancel bool
}

// Stage of a Window.
type Stage uint8

// CommandType is the type of a CommandEvent.
type CommandType uint8

const (
	// StagePaused is the Stage for inactive Windows.
	// Inactive Windows don't receive FrameEvents.
	StagePaused Stage = iota
	// StateRunning is for active Windows.
	StageRunning
)

const (
	// CommandBack is the command for a back action
	// such as the Android back button.
	CommandBack CommandType = iota
)

But now the system.CommandEvent and system.CommandBack have been removed in gioui.org/io/system/system.go(v0.0.0-20220425071242-aa14056350d6)

So how can I handle the BackButton in android?
Could you restore the system.CommandEvent and system.CommandBack in gioui.org/io/system/system.go?

[diyism]

https://todo.sr.ht/~eliasnaur/gio/408