package tomo

import "image"
import "errors"

var backend Backend

// Run initializes a backend, runs the specified callback function, and runs the
// event loop in that order. This function blocks until Stop is called, or the
// backend experiences a fatal error.
func Run (callback func ()) error {
	if backend != nil {
		return errors.New("there is already a backend running")
	}

	back, err := Initialize()
	if err != nil { return err }
	backend = back

	callback()
	return backend.Run()
}

func assertBackend () {
	if backend == nil { panic("nil backend") }
}

// Stop stops the backend, unblocking run. Run may be called again after calling
// Stop.
func Stop () {
	assertBackend()
	backend.Stop()
	backend = nil
}

func NewWindow (bounds image.Rectangle) MainWindow {
	assertBackend()
	return backend.NewWindow(bounds)
}

func NewBox () Box {
	assertBackend()
	return backend.NewBox()
}

func NewTextBox () TextBox {
	assertBackend()
	return backend.NewTextBox()
}

func NewCanvasBox () CanvasBox {
	assertBackend()
	return backend.NewCanvasBox()
}

func NewContainerBox () ContainerBox {
	assertBackend()
	return backend.NewContainerBox()
}