80 lines
1.8 KiB
Go
80 lines
1.8 KiB
Go
package widgets
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import (
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"sync/atomic"
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"github.com/dweymouth/supersonic/backend/mediaprovider"
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)
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// Component that manages lazily loading more tracks into a Tracklist
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// as the user scrolls near the bottom.
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type TracklistLoader struct {
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disposed atomic.Bool
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tracklist *Tracklist
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iter mediaprovider.TrackIterator
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trackBuffer []*mediaprovider.Track
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fetching bool
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done bool
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len int
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highestShown int
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}
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func NewTracklistLoader(tracklist *Tracklist, iter mediaprovider.TrackIterator) *TracklistLoader {
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t := TracklistLoader{
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tracklist: tracklist,
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iter: iter,
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}
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t.tracklist.OnTrackShown = t.onTrackShown
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t.fetching = true
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go t.loadMoreTracks(25)
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return &t
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}
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// Cancels all asynchronous loads so that they will no longer modify the tracklist.
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func (t *TracklistLoader) Dispose() {
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t.disposed.Store(true)
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t.tracklist.OnTrackShown = nil
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}
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func (t *TracklistLoader) onTrackShown(tracknum int) {
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if tracknum > t.highestShown {
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t.highestShown = tracknum
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}
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if t.highestShown >= t.len-25 && !t.fetching && !t.done && !t.disposed.Load() {
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t.fetching = true
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go t.loadMoreTracks(25)
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}
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}
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func (t *TracklistLoader) loadMoreTracks(num int) {
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// repeat fetch task as long as user has scrolled near bottom
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for !t.done && t.highestShown >= t.len-25 {
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if t.trackBuffer == nil {
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t.trackBuffer = make([]*mediaprovider.Track, 0, num)
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}
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t.trackBuffer = t.trackBuffer[:0]
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for i := 0; i < num; i++ {
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tr := t.iter.Next()
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if tr == nil {
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t.done = true
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break
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}
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t.trackBuffer = append(t.trackBuffer, tr)
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if t.disposed.Load() {
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break
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}
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}
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if t.disposed.Load() {
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return
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}
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t.tracklist.AppendTracks(t.trackBuffer)
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t.len += len(t.trackBuffer)
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}
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if t.done {
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t.trackBuffer = nil
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}
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t.fetching = false
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}
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