Split into category packages; module github.com/ZacharyZhang-NY/MujicaUI

chat/streaming_text.go

@@ -0,0 +1,79 @@
+package chat
+
+import (
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/egoist/mygo/ui"
+
+	"github.com/ZacharyZhang-NY/MujicaUI/core"
+)
+
+// StreamingTextOptions configure a StreamingText.
+type StreamingTextOptions struct {
+	// Streaming shows the cursor after the text while more is coming.
+	Streaming bool
+	// Smooth reveals new text gradually instead of at once.
+	Smooth bool
+	// Rate is the smooth reveal speed in characters per second; zero means 80.
+	Rate float64
+}
+
+// streamingState is how much of the text shows, and since when.
+type streamingState struct {
+	text  string
+	shown float64
+	at    time.Time
+}
+
+// StreamingText shows text that grows as it streams; reduced motion shows it at once.
+func StreamingText(c *ui.Context, text string, opts StreamingTextOptions) *ui.Element {
+	if opts.Rate < 0 {
+		panic("mujica: StreamingText Rate must not be negative")
+	}
+	rate := opts.Rate
+	if rate == 0 {
+		rate = 80
+	}
+	k := core.Tokens(c)
+	e := ui.Box(c).Label(text)
+	st := ui.Local(e, "stream", func() streamingState {
+		return streamingState{text: text, shown: float64(utf8.RuneCountInString(text)), at: c.Now()}
+	})
+	total := float64(utf8.RuneCountInString(text))
+	if !strings.HasPrefix(text, st.text) {
+		// Replaced text starts over from what it shares.
+		st.shown = min(st.shown, float64(utf8.RuneCountInString(streamingCommon(st.text, text))))
+	}
+	st.text = text
+	now := c.Now()
+	if !opts.Smooth || core.Motion(c, time.Second) == 0 {
+		st.shown = total
+	} else if st.shown < total {
+		st.shown = min(total, st.shown+now.Sub(st.at).Seconds()*rate)
+		c.AnimationFrame()
+	}
+	st.at = now
+	shown := text
+	if n := int(st.shown); n < int(total) {
+		shown = string([]rune(text)[:n])
+	}
+	spans := []ui.Span{{Text: shown}}
+	if opts.Streaming {
+		spans = append(spans, ui.Span{Text: "▍", Color: k.AccentText})
+	}
+	return e.Children(func() { ui.RichText(c, spans...) })
+}
+
+// streamingCommon returns the longest common prefix of a and b, on rune boundaries.
+func streamingCommon(a, b string) string {
+	n := 0
+	for n < len(a) && n < len(b) && a[n] == b[n] {
+		n++
+	}
+	for n > 0 && n < len(a) && !utf8.RuneStart(a[n]) {
+		n--
+	}
+	return a[:n]
+}