93 lines
2.9 KiB
Dart
93 lines
2.9 KiB
Dart
import 'dart:typed_data';
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import 'dart:ui' as ui show Codec;
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import 'package:aves/model/image_entry.dart';
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import 'package:aves/services/image_file_service.dart';
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import 'package:flutter/foundation.dart';
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import 'package:flutter/material.dart';
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class ThumbnailProvider extends ImageProvider<ThumbnailProviderKey> {
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ThumbnailProvider({
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@required this.entry,
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this.extent = 0,
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this.scale = 1,
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}) : assert(entry != null),
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assert(extent != null),
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assert(scale != null) {
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_cancellationKey = _buildKey(ImageConfiguration.empty);
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}
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final ImageEntry entry;
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final double extent;
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final double scale;
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Object _cancellationKey;
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@override
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Future<ThumbnailProviderKey> obtainKey(ImageConfiguration configuration) {
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// configuration can be empty (e.g. when obtaining key for eviction)
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// so we do not compute the target width/height here
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// and pass it to the key, to use it later for image loading
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return SynchronousFuture<ThumbnailProviderKey>(_buildKey(configuration));
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}
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ThumbnailProviderKey _buildKey(ImageConfiguration configuration) => ThumbnailProviderKey(
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entry: entry,
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extent: extent,
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scale: scale,
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);
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@override
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ImageStreamCompleter load(ThumbnailProviderKey key, DecoderCallback decode) {
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return MultiFrameImageStreamCompleter(
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codec: _loadAsync(key, decode),
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scale: key.scale,
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informationCollector: () sync* {
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yield ErrorDescription('uri=${entry.uri}, extent=$extent');
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},
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);
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}
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Future<ui.Codec> _loadAsync(ThumbnailProviderKey key, DecoderCallback decode) async {
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final bytes = await ImageFileService.getThumbnail(key.entry, extent, extent, taskKey: _cancellationKey);
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return await decode(bytes ?? Uint8List(0));
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}
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@override
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void resolveStreamForKey(ImageConfiguration configuration, ImageStream stream, ThumbnailProviderKey key, ImageErrorListener handleError) {
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ImageFileService.resumeThumbnail(_cancellationKey);
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super.resolveStreamForKey(configuration, stream, key, handleError);
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}
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void pause() => ImageFileService.cancelThumbnail(_cancellationKey);
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}
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class ThumbnailProviderKey {
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final ImageEntry entry;
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final double extent;
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final double scale;
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// do not access `contentId` via `entry` for hashCode and equality purposes
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// as an entry is not constant and its contentId can change
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final int contentId;
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ThumbnailProviderKey({
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@required this.entry,
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@required this.extent,
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this.scale,
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}) : contentId = entry.contentId;
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@override
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bool operator ==(Object other) {
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if (other.runtimeType != runtimeType) return false;
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return other is ThumbnailProviderKey && other.contentId == contentId && other.extent == extent && other.scale == scale;
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}
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@override
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int get hashCode => hashValues(contentId, extent, scale);
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@override
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String toString() {
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return 'ThumbnailProviderKey{contentId=$contentId, extent=$extent, scale=$scale}';
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}
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}
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