88 lines
2.3 KiB
Go
88 lines
2.3 KiB
Go
package mujica
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import (
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"log/slog"
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"strings"
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"time"
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"github.com/egoist/mygo/ui"
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)
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// TypewriterOptions configure a Typewriter.
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type TypewriterOptions struct {
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// Speed is characters per second; zero means 40.
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Speed float64
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// Skippable adds a Skip button that shows the rest at once.
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Skippable bool
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}
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// TypewriterResult is a built Typewriter and its events.
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type TypewriterResult struct {
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Element *ui.Element
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done bool
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}
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// Finished reports the frame the whole text came into view.
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func (r TypewriterResult) Finished() bool { return r.done }
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type typewriterState struct {
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text []rune
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shown int
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last time.Time
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skipped bool
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done bool
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}
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// Typewriter reveals text a character at a time; text that grows continues where it was.
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func Typewriter(c *ui.Context, text string, opts TypewriterOptions) TypewriterResult {
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speed := opts.Speed
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if speed == 0 {
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speed = 40
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}
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if speed < 0 {
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panic("mujica: Typewriter Speed is negative")
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}
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col := ui.Column(c).AlignItems(ui.Start).Gap(Density(c).Unit() * 2).Role(ui.RoleGroup).Label(text)
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res := TypewriterResult{Element: col}
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st := ui.Local(col, "typing", func() *typewriterState { return &typewriterState{last: c.Now()} })
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s := *st
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runes := []rune(text)
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if !strings.HasPrefix(text, string(s.text)) {
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s.shown, s.skipped, s.done = 0, false, false
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slog.Debug("mujica: typewriter restart")
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}
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if len(runes) > len(s.text) && s.done {
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// New text continues from where it stood, at the typing speed.
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s.done, s.skipped, s.last = false, false, c.Now()
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}
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s.text = runes
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now := c.Now()
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if c.Preferences().ReduceMotion || s.skipped {
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s.shown = len(runes)
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} else if s.shown < len(runes) {
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step := time.Duration(float64(time.Second) / speed)
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if n := int(now.Sub(s.last) / step); n > 0 {
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s.shown = min(len(runes), s.shown+n)
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s.last = s.last.Add(time.Duration(n) * step)
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}
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if s.shown < len(runes) {
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c.After(s.last.Add(step).Sub(now))
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}
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} else {
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s.last = now
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}
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col.Children(func() {
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ui.Text(c, string(runes[:s.shown]))
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if opts.Skippable && s.shown < len(runes) {
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if Button(c, msg(c, "typewriter.skip"), ButtonOptions{Variant: Ghost}).Clicked() {
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s.skipped, s.shown = true, len(runes)
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slog.Debug("mujica: typewriter skip")
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}
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}
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})
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if s.shown == len(runes) && !s.done {
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s.done, res.done = true, true
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}
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return res
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}
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