Buffer/ticker-based renderer

renderer.go

@@ -0,0 +1,99 @@
+package tea
+
+import (
+	"bytes"
+	"io"
+	"sync"
+	"time"
+
+	"github.com/muesli/termenv"
+)
+
+const (
+	defaultFramerate = time.Millisecond * 16
+)
+
+type renderer struct {
+	out           io.Writer
+	buf           bytes.Buffer
+	framerate     time.Duration
+	ticker        *time.Ticker
+	mtx           sync.Mutex
+	done          chan struct{}
+	lastRender    string
+	linesRendered int
+}
+
+func newRenderer(out io.Writer) *renderer {
+	return &renderer{
+		out:       out,
+		framerate: defaultFramerate,
+	}
+}
+
+func (r *renderer) start() {
+	if r.ticker == nil {
+		r.ticker = time.NewTicker(r.framerate)
+	}
+	r.done = make(chan struct{})
+	go r.listen()
+}
+
+func (r *renderer) stop() {
+	r.flush()
+	r.done <- struct{}{}
+}
+
+func (r *renderer) listen() {
+	for {
+		select {
+		case <-r.ticker.C:
+			if r.ticker != nil {
+				r.flush()
+			}
+		case <-r.done:
+			r.mtx.Lock()
+			r.ticker.Stop()
+			r.ticker = nil
+			r.mtx.Unlock()
+			close(r.done)
+			return
+		}
+	}
+}
+
+func (r *renderer) flush() {
+	if r.buf.Len() == 0 || r.buf.String() == r.lastRender {
+		// Nothing to do
+		return
+	}
+
+	r.mtx.Lock()
+	defer r.mtx.Unlock()
+
+	if r.linesRendered > 0 {
+		termenv.ClearLines(r.linesRendered)
+	}
+	r.linesRendered = 0
+
+	var out bytes.Buffer
+	for _, b := range r.buf.Bytes() {
+		if b == '\n' {
+			r.linesRendered++
+			out.Write([]byte("\r\n"))
+		} else {
+			// TODO: don't write past the terminal width
+			_, _ = out.Write([]byte{b})
+		}
+	}
+
+	_, _ = r.out.Write(out.Bytes())
+	r.lastRender = r.buf.String()
+	r.buf.Reset()
+}
+
+func (w *renderer) write(s string) {
+	w.mtx.Lock()
+	defer w.mtx.Unlock()
+	w.buf.WriteString(s)
+}