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gridview.go
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gridview.go
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package widgets
import (
"context"
"image"
"log"
"sync"
"github.com/dweymouth/supersonic/backend/mediaprovider"
"github.com/dweymouth/supersonic/sharedutil"
"fyne.io/fyne/v2"
"fyne.io/fyne/v2/widget"
xwidget "fyne.io/x/fyne/widget"
)
const batchFetchSize = 6
type BatchingIterator struct {
iter mediaprovider.AlbumIterator
}
func NewBatchingIterator(iter mediaprovider.AlbumIterator) BatchingIterator {
return BatchingIterator{iter}
}
func (b *BatchingIterator) NextN(n int) []*mediaprovider.Album {
results := make([]*mediaprovider.Album, 0, n)
i := 0
for i < n {
album := b.iter.Next()
if album == nil {
break
}
results = append(results, album)
i++
}
return results
}
type ImageFetcher interface {
GetCoverThumbnailFromCache(string) (image.Image, bool)
GetCoverThumbnailAsync(string, func(image.Image, error)) context.CancelFunc
}
type GridViewIterator interface {
NextN(int) []GridViewItemModel
}
type gridViewAlbumIterator struct {
iter BatchingIterator
}
func (g gridViewAlbumIterator) NextN(n int) []GridViewItemModel {
albums := g.iter.NextN(n)
return sharedutil.MapSlice(albums, func(al *mediaprovider.Album) GridViewItemModel {
return GridViewItemModel{
Name: al.Name,
ID: al.ID,
CoverArtID: al.CoverArtID,
Secondary: al.ArtistNames[0],
SecondaryID: al.ArtistIDs[0],
}
})
}
func NewGridViewAlbumIterator(iter mediaprovider.AlbumIterator) GridViewIterator {
return gridViewAlbumIterator{iter: NewBatchingIterator(iter)}
}
type GridView struct {
widget.BaseWidget
stateMutex sync.RWMutex
fetchCancel context.CancelFunc
GridViewState
grid *xwidget.GridWrap
menu *widget.PopUpMenu
menuGridViewItemId string
}
type GridViewState struct {
items []GridViewItemModel
iter GridViewIterator
imageFetcher ImageFetcher
Placeholder fyne.Resource
highestShown int
done bool
OnPlay func(id string, shuffle bool)
OnAddToQueue func(id string)
OnAddToPlaylist func(id string)
OnDownload func(id string)
OnShowItemPage func(id string)
OnShowSecondaryPage func(id string)
scrollPos float32
}
var _ fyne.Widget = (*GridView)(nil)
func NewFixedGridView(items []GridViewItemModel, fetch ImageFetcher, placeholder fyne.Resource) *GridView {
g := &GridView{
GridViewState: GridViewState{
items: items,
done: true,
imageFetcher: fetch,
Placeholder: placeholder,
},
}
g.ExtendBaseWidget(g)
g.createGridWrap()
return g
}
func NewGridView(iter GridViewIterator, fetch ImageFetcher, placeholder fyne.Resource) *GridView {
g := &GridView{
GridViewState: GridViewState{
iter: iter,
imageFetcher: fetch,
Placeholder: placeholder,
},
}
g.ExtendBaseWidget(g)
g.createGridWrap()
// fetch initial items
g.checkFetchMoreItems(36)
return g
}
func (g *GridView) SaveToState() *GridViewState {
g.stateMutex.RLock()
s := g.GridViewState
g.stateMutex.RUnlock()
s.scrollPos = g.grid.GetScrollOffset()
return &s
}
func NewGridViewFromState(state *GridViewState) *GridView {
g := &GridView{GridViewState: *state}
g.ExtendBaseWidget(g)
g.createGridWrap()
g.Refresh() // needed to initialize the widget
g.grid.ScrollToOffset(state.scrollPos)
return g
}
func (g *GridView) Clear() {
g.stateMutex.Lock()
defer g.stateMutex.Unlock()
g.cancelFetch()
g.items = nil
g.done = true
}
func (g *GridView) Reset(iter GridViewIterator) {
g.stateMutex.Lock()
g.cancelFetch()
g.items = nil
g.done = false
g.highestShown = 0
g.iter = iter
g.stateMutex.Unlock()
g.checkFetchMoreItems(36)
g.Refresh()
}
func (g *GridView) ResetFromState(state *GridViewState) {
g.stateMutex.Lock()
g.cancelFetch()
g.GridViewState = *state
g.stateMutex.Unlock()
g.grid.Refresh()
g.grid.ScrollToOffset(state.scrollPos)
g.grid.Refresh()
}
func (g *GridView) ResetFixed(items []GridViewItemModel) {
g.stateMutex.Lock()
g.cancelFetch()
g.items = items
g.done = true
g.highestShown = 0
g.iter = nil
g.stateMutex.Unlock()
g.Refresh()
}
func (g *GridView) GetScrollOffset() float32 {
return g.grid.GetScrollOffset()
}
func (g *GridView) ScrollToOffset(offs float32) {
g.grid.ScrollToOffset(offs)
}
func (g *GridView) createGridWrap() {
g.grid = xwidget.NewGridWrap(
func() int {
return g.lenItems()
},
// create func
func() fyne.CanvasObject {
card := NewGridViewItem(g.Placeholder)
card.OnPlay = func() { g.onPlay(card.ItemID(), false) }
card.OnShowSecondaryPage = func() {
if g.OnShowSecondaryPage != nil {
g.OnShowSecondaryPage(card.SecondaryID())
}
}
card.OnShowItemPage = func() {
if g.OnShowItemPage != nil {
g.OnShowItemPage(card.ItemID())
}
}
card.OnShowContextMenu = func(p fyne.Position) {
g.showContextMenu(card, p)
}
return card
},
// update func
func(itemID xwidget.GridWrapItemID, obj fyne.CanvasObject) {
ac := obj.(*GridViewItem)
g.doUpdateItemCard(int(itemID), ac)
},
)
}
func (g *GridView) doUpdateItemCard(itemIdx int, card *GridViewItem) {
if itemIdx > g.highestShown {
g.highestShown = itemIdx
}
var item GridViewItemModel
g.stateMutex.RLock()
// itemIdx can rarely be out of range if the data is being updated
// as the view is requested to refresh
if itemIdx < len(g.items) {
item = g.items[itemIdx]
}
g.stateMutex.RUnlock()
card.Cover.Im.CenterIcon = g.Placeholder
if !card.NeedsUpdate(item) {
// nothing to do
return
}
card.Update(item)
// cancel any previous image fetch (no issues with possible double-invocations)
if card.ImgLoadCancel != nil {
card.ImgLoadCancel()
}
if item.CoverArtID != "" {
if img, ok := g.imageFetcher.GetCoverThumbnailFromCache(item.CoverArtID); ok {
card.Cover.SetImage(img)
} else {
card.Cover.SetImage(nil)
card.ImgLoadCancel = g.imageFetcher.GetCoverThumbnailAsync(item.CoverArtID, func(i image.Image, err error) {
if err == nil {
card.Cover.SetImage(i)
} else {
log.Printf("error fetching image: %s", err.Error())
}
card.ImgLoadCancel() // done. release resources associated with cancel channel
})
}
} else {
// use the placeholder for an item that has no cover art ID
card.Cover.SetImage(nil)
}
// if user has scrolled near the bottom, fetch more
if itemIdx > g.lenItems()-10 {
g.checkFetchMoreItems(20)
}
}
func (g *GridView) lenItems() int {
g.stateMutex.RLock()
defer g.stateMutex.RUnlock()
return len(g.items)
}
// fetches at least count more items if fetch not in progress and not done
// acquires stateMutex for atomicity
func (g *GridView) checkFetchMoreItems(count int) {
g.stateMutex.Lock()
defer g.stateMutex.Unlock()
if g.done || g.fetchCancel != nil {
return // done, or fetch already in progress
}
if g.iter == nil {
g.done = true
return
}
ctx, cancel := context.WithCancel(context.Background())
g.fetchCancel = cancel
go func() {
// keep repeating the fetch task as long as the user
// has scrolled near the bottom
for !g.done && g.highestShown >= g.lenItems()-10 {
n := 0
for !g.done && n < count {
items := g.iter.NextN(batchFetchSize)
select {
case <-ctx.Done():
return
default:
g.stateMutex.Lock()
g.items = append(g.items, items...)
g.stateMutex.Unlock()
if len(items) < batchFetchSize {
g.done = true
}
n += len(items)
if len(items) > 0 {
g.grid.Refresh()
}
}
}
}
// call cancelfunc to release Context resources
g.stateMutex.Lock()
g.cancelFetch()
g.stateMutex.Unlock()
}()
}
// must be called with stateMutex locked for writing
func (g *GridView) cancelFetch() {
if g.fetchCancel != nil {
g.fetchCancel()
g.fetchCancel = nil
}
}
func (g *GridView) showContextMenu(card *GridViewItem, pos fyne.Position) {
g.menuGridViewItemId = card.ItemID()
if g.menu == nil {
g.menu = widget.NewPopUpMenu(fyne.NewMenu("",
fyne.NewMenuItem("Play", func() { g.onPlay(g.menuGridViewItemId, false) }),
fyne.NewMenuItem("Shuffle", func() { g.onPlay(g.menuGridViewItemId, true) }),
fyne.NewMenuItem("Add to queue", func() {
if g.OnAddToQueue != nil {
g.OnAddToQueue(g.menuGridViewItemId)
}
}),
fyne.NewMenuItem("Add to playlist...", func() {
if g.OnAddToPlaylist != nil {
g.OnAddToPlaylist(g.menuGridViewItemId)
}
}),
fyne.NewMenuItem("Download...", func() {
if g.OnDownload != nil {
g.OnDownload(g.menuGridViewItemId)
}
})),
fyne.CurrentApp().Driver().CanvasForObject(g))
}
g.menu.ShowAtPosition(pos)
}
func (g *GridView) onPlay(itemID string, shuffle bool) {
if g.OnPlay != nil {
g.OnPlay(itemID, shuffle)
}
}
func (g *GridView) CreateRenderer() fyne.WidgetRenderer {
return widget.NewSimpleRenderer(g.grid)
}