hellojukay@local test $ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/hellojukay/.cache/go-build"
GOENV="/home/hellojukay/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"

package main

import (
	"flag"
	"io"
	"log"
	"os"

	"github.com/mjl-/duit"
)

func check(err error, msg string) {
	if err != nil {
		log.Fatalf("%s: %s\n", msg, err)
	}
}

func main() {
	log.SetFlags(0)
	flag.Usage = func() {
		log.Println("usage: duitedit file")
		flag.PrintDefaults()
	}
	flag.Parse()
	args := flag.Args()
	if len(args) != 1 {
		flag.Usage()
		os.Exit(2)
	}

	f, err := os.Open(args[0])
	check(err, "open")

	dui, err := duit.NewDUI("ex/edit", nil)
	check(err, "new dui")

	edit, err := duit.NewEdit(f)
	check(err, "new edit")

	print := &duit.Button{
		Text: "print",
		Click: func() (e duit.Event) {
			rd := edit.Reader()
			n, err := io.Copy(os.Stdout, rd)
			if err != nil {
				log.Printf("error copying text: %s\n", err)
			}
			log.Printf("copied %d bytes\n", n)
			return
		},
	}

	dui.Top.UI = &duit.Box{Kids: duit.NewKids(print, edit)}
	dui.Render()

	for {
		select {
		case e := <-dui.Inputs:
			dui.Input(e)

		case err, ok := <-dui.Error:
			if !ok {
				return
			}
			log.Printf("duit: %s\n", err)
		}
	}
}

hellojukay@local test $ go build main.go 
hellojukay@local test $ ./main 
usage: duitedit file
hellojukay@local test $ ./main main.go 
new dui: drawfcall.New: exec: "devdraw": executable file not found in $PATH