Add nil renderer and combination TUI-daemon program example

The Nil Renderer essentially disables the Bubble Tea renderer sending
loggings and print statements to stdout. It can be enabled via the
ProgramOption WithoutRenderer.

examples/go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/charmbracelet/glamour v0.2.0
 	github.com/fogleman/ease v0.0.0-20170301025033-8da417bf1776
 	github.com/lucasb-eyer/go-colorful v1.0.3
+	github.com/mattn/go-isatty v0.0.12
 	github.com/mattn/go-runewidth v0.0.10
 	github.com/muesli/reflow v0.2.1-0.20210115123740-9e1d0d53df68
 	github.com/muesli/termenv v0.7.4

examples/tui-daemon-combo/main.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"os"
+	"time"
+
+	"github.com/charmbracelet/bubbles/spinner"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/mattn/go-isatty"
+	"github.com/muesli/reflow/indent"
+)
+
+func main() {
+	rand.Seed(time.Now().UTC().UnixNano())
+
+	var (
+		daemonMode bool
+		showHelp   bool
+		opts       []tea.ProgramOption
+	)
+
+	flag.BoolVar(&daemonMode, "d", false, "run as a daemon")
+	flag.BoolVar(&showHelp, "h", false, "show help")
+	flag.Parse()
+
+	if showHelp {
+		flag.Usage()
+		os.Exit(0)
+	}
+
+	if daemonMode || !isatty.IsTerminal(os.Stdout.Fd()) {
+		// If we're in daemon mode don't render the TUI
+		opts = []tea.ProgramOption{tea.WithoutRenderer()}
+	} else {
+		// If we're in TUI mode, discard log output
+		log.SetOutput(ioutil.Discard)
+	}
+
+	p := tea.NewProgram(newModel(), opts...)
+	if err := p.Start(); err != nil {
+		fmt.Println("Error starting Bubble Tea program:", err)
+		os.Exit(1)
+	}
+}
+
+type model struct {
+	spinner  spinner.Model
+	results  []time.Duration
+	quitting bool
+}
+
+func newModel() model {
+	const showLastResults = 5
+
+	return model{
+		spinner: spinner.NewModel(),
+		results: make([]time.Duration, showLastResults),
+	}
+}
+
+func (m model) Init() tea.Cmd {
+	log.Println("Starting work...")
+	return tea.Batch(
+		spinner.Tick,
+		runPretendProcess,
+	)
+}
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		m.quitting = true
+		return m, tea.Quit
+	case spinner.TickMsg:
+		var cmd tea.Cmd
+		m.spinner, cmd = m.spinner.Update(msg)
+		return m, cmd
+	case processFinishedMsg:
+		d := time.Duration(msg)
+		log.Printf("Finished job in %s", d)
+		m.results = append(m.results[1:], d)
+		return m, runPretendProcess
+	default:
+		return m, nil
+	}
+}
+
+func (m model) View() string {
+	s := "\n" + m.spinner.View() + " Doing some work...\n\n"
+
+	for _, dur := range m.results {
+		if dur == 0 {
+			s += ".....................\n"
+		} else {
+			s += fmt.Sprintf("Job finished in %s\n", dur)
+		}
+	}
+
+	s += "\nPress any key to exit\n"
+
+	if m.quitting {
+		s += "\n"
+	}
+
+	return indent.String(s, 1)
+}
+
+// processFinishedMsg is send when a pretend process completes.
+type processFinishedMsg time.Duration
+
+// pretendProcess simulates a long-running process.
+func runPretendProcess() tea.Msg {
+	pause := time.Duration(rand.Int63n(899)+100) * time.Millisecond
+	time.Sleep(pause)
+	return processFinishedMsg(pause)
+}