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