110 lines
3.5 KiB
Dart
110 lines
3.5 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:aves/services/service_policy.dart';
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import 'package:flutter/foundation.dart';
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import 'package:flutter/material.dart';
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import 'package:uuid/uuid.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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@required this.extent,
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this.scale = 1.0,
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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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final ImageEntry entry;
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final double extent;
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final double scale;
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final Object _cancellationKey = Uuid();
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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>(ThumbnailProviderKey(
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entry: entry,
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extent: extent,
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devicePixelRatio: configuration.devicePixelRatio,
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scale: scale,
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));
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}
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@override
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ImageStreamCompleter load(ThumbnailProviderKey key, DecoderCallback decode) {
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return CancellableMultiFrameImageStreamCompleter(
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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 dimPixels = (extent * key.devicePixelRatio).round();
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final bytes = await ImageFileService.getThumbnail(key.entry, dimPixels, dimPixels, cancellationKey: _cancellationKey);
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return await decode(bytes ?? Uint8List(0));
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}
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Future<void> cancel() async {
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if (servicePolicy.cancel(_cancellationKey)) {
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await evict();
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}
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}
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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 devicePixelRatio; // do not include configuration in key hashcode or == operator
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final double scale;
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const ThumbnailProviderKey({
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@required this.entry,
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@required this.extent,
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@required this.devicePixelRatio,
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this.scale,
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});
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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.entry.uri == entry.uri && other.extent == extent && other.scale == scale;
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}
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@override
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int get hashCode => hashValues(entry.uri, extent, scale);
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@override
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String toString() {
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return 'ThumbnailProviderKey{uri=${entry.uri}, extent=$extent, scale=$scale}';
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}
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}
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class CancellableMultiFrameImageStreamCompleter extends MultiFrameImageStreamCompleter {
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CancellableMultiFrameImageStreamCompleter({
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@required Future<ui.Codec> codec,
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@required double scale,
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Stream<ImageChunkEvent> chunkEvents,
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InformationCollector informationCollector,
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}) : super(
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codec: codec,
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scale: scale,
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chunkEvents: chunkEvents,
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informationCollector: informationCollector,
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);
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@override
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void reportError({DiagnosticsNode context, dynamic exception, StackTrace stack, informationCollector, bool silent = false}) {
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// prevent default error reporting in case of planned cancellation
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if (exception is CancelledException) return;
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super.reportError(context: context, exception: exception, stack: stack, informationCollector: informationCollector, silent: silent);
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}
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}
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