From d3a66e310732be89795b1200f3c867386ded4271 Mon Sep 17 00:00:00 2001
From: Ferhat <ferhat@gmail.com>
Date: Tue, 17 Mar 2020 16:07:21 -0700
Subject: [PATCH] [web] Add support for ChunkEvents during image loading
 (#52558)

* Add support for ChunkEvents for web
* Add lint skip for webOnly call in _network_image_web
---
 .../lib/src/painting/_network_image_web.dart  | 57 ++++++++++++++-----
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/packages/flutter/lib/src/painting/_network_image_web.dart b/packages/flutter/lib/src/painting/_network_image_web.dart
index 8641e213930..2e9771b50f7 100644
--- a/packages/flutter/lib/src/painting/_network_image_web.dart
+++ b/packages/flutter/lib/src/painting/_network_image_web.dart
@@ -13,7 +13,9 @@ import 'image_stream.dart';
 /// The dart:html implementation of [image_provider.NetworkImage].
 ///
 /// NetworkImage on the web does not support decoding to a specified size.
-class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkImage> implements image_provider.NetworkImage {
+class NetworkImage
+    extends image_provider.ImageProvider<image_provider.NetworkImage>
+    implements image_provider.NetworkImage {
   /// Creates an object that fetches the image at the given URL.
   ///
   /// The arguments [url] and [scale] must not be null.
@@ -31,22 +33,41 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
   final Map<String, String> headers;
 
   @override
-  Future<NetworkImage> obtainKey(image_provider.ImageConfiguration configuration) {
+  Future<NetworkImage> obtainKey(
+      image_provider.ImageConfiguration configuration) {
     return SynchronousFuture<NetworkImage>(this);
   }
 
   @override
-  ImageStreamCompleter load(image_provider.NetworkImage key, image_provider.DecoderCallback decode) {
+  ImageStreamCompleter load(
+      image_provider.NetworkImage key, image_provider.DecoderCallback decode) {
+    // Ownership of this controller is handed off to [_loadAsync]; it is that
+    // method's responsibility to close the controller's stream when the image
+    // has been loaded or an error is thrown.
+    final StreamController<ImageChunkEvent> chunkEvents =
+        StreamController<ImageChunkEvent>();
+
     return MultiFrameImageStreamCompleter(
-      codec: _loadAsync(key as NetworkImage, decode),
-      scale: key.scale,
-      informationCollector: () {
+        chunkEvents: chunkEvents.stream,
+        codec: _loadAsync(key as NetworkImage, decode, chunkEvents),
+        scale: key.scale,
+        informationCollector: _imageStreamInformationCollector(key));
+  }
+
+  InformationCollector _imageStreamInformationCollector(
+      image_provider.NetworkImage key) {
+    InformationCollector collector;
+    assert(() {
+      collector = () {
         return <DiagnosticsNode>[
-          DiagnosticsProperty<image_provider.ImageProvider>('Image provider', this),
+          DiagnosticsProperty<image_provider.ImageProvider>(
+              'Image provider', this),
           DiagnosticsProperty<NetworkImage>('Image key', key as NetworkImage),
         ];
-      },
-    );
+      };
+      return true;
+    }());
+    return collector;
   }
 
   // TODO(garyq): We should eventually support custom decoding of network images on Web as
@@ -55,13 +76,20 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
   // Web does not support decoding network images to a specified size. The decode parameter
   // here is ignored and the web-only `ui.webOnlyInstantiateImageCodecFromUrl` will be used
   // directly in place of the typical `instantiateImageCodec` method.
-  Future<ui.Codec> _loadAsync(NetworkImage key, image_provider.DecoderCallback decode) {
+  Future<ui.Codec> _loadAsync(
+      NetworkImage key,
+      image_provider.DecoderCallback decode,
+      StreamController<ImageChunkEvent> chunkEvents) {
     assert(key == this);
 
     final Uri resolved = Uri.base.resolve(key.url);
     // This API only exists in the web engine implementation and is not
     // contained in the analyzer summary for Flutter.
-    return ui.webOnlyInstantiateImageCodecFromUrl(resolved) as Future<ui.Codec>; // ignore: undefined_function
+    return ui.webOnlyInstantiateImageCodecFromUrl(resolved, // ignore: undefined_function
+        chunkCallback: (int bytes, int total) {
+      chunkEvents.add(ImageChunkEvent(
+          cumulativeBytesLoaded: bytes, expectedTotalBytes: total));
+    }) as Future<ui.Codec>; // ignore: undefined_function
   }
 
   @override
@@ -69,14 +97,13 @@ class NetworkImage extends image_provider.ImageProvider<image_provider.NetworkIm
     if (other.runtimeType != runtimeType) {
       return false;
     }
-    return other is NetworkImage
-        && other.url == url
-        && other.scale == scale;
+    return other is NetworkImage && other.url == url && other.scale == scale;
   }
 
   @override
   int get hashCode => ui.hashValues(url, scale);
 
   @override
-  String toString() => '${objectRuntimeType(this, 'NetworkImage')}("$url", scale: $scale)';
+  String toString() =>
+      '${objectRuntimeType(this, 'NetworkImage')}("$url", scale: $scale)';
 }