feat: enable Impeller and add workaround for broken image

This commit brings Impeller back to Android again.

Specific image is broken with Impeller backend, no similar issues found
on issue tracker. To prepare for the upcoming stable release in August,
enable impeller on Android is required. For the broken image issue, till
now we only found the redirect back icon in static server resource is
affected, so this commit adds a workaround for it: instead of render the
original image, replace it with icon and icon button. This change is
what we DO NOT intend but have to, another possible workaround is on the
cache layer, but it is less semantic for users.

Author: realth000

android/app/src/main/AndroidManifest.xml

@@ -34,8 +34,5 @@
         <meta-data
                 android:name="flutterEmbedding"
                 android:value="2"/>
-        <meta-data
-                android:name="io.flutter.embedding.android.EnableImpeller"
-                android:value="false"/>
     </application>
 </manifest>

lib/constants/url.dart

@@ -81,6 +81,16 @@ String formatReplyThreadUrl(String fid, String tid) {
 /// Prefix in url to get fast reply window to a certain post.
 const replyPostWindowSuffix = '&infloat=yes&handlekey=reply&inajax=1&ajaxtarget=fwin_content_reply';
 
+/// Url of images have rendering issue with Impeller.
+///
+/// The root cause is not clear, maybe corrupt cache content, but it works with skia backend so should not be it.
+/// Since these images are now for redirect back purpose, we could handle them specially although we didn't intend to
+/// do it before, we have to do it before the next upcoming stable release of Flutter in August, 2025.
+const tmpImpellerWorkaroundUrls = [
+  'https://$baseHost/static/image/common/back.gif',
+  'https://$baseHostAlt/static/image/common/back.gif',
+];
+
 /// Target url to post a reply to another post in thread [tid], forum [fid].
 String formatReplyPostUrl(String fid, String tid) {
   return '$homePage?mod=post&infloat=yes&action=reply&fid=$fid&'

lib/i18n/en.i18n.json

@@ -1148,5 +1148,6 @@
     "notReplyToFloorTip": "Not reply to this floor",
     "expandToolbarTip": "Expand toolbar",
     "collapseToolbarTip": "Collapse toolbar"
-  }
+  },
+  "workaroundRedirect": "View conversation"
 }

lib/i18n/zh-CN.i18n.json

@@ -1148,5 +1148,6 @@
     "notReplyToFloorTip": "不回复该楼层（改为回复楼主）",
     "expandToolbarTip": "展开工具栏",
     "collapseToolbarTip": "收起工具栏"
-  }
+  },
+  "workaroundRedirect": "查看对话"
 }

lib/i18n/zh-TW.i18n.json

@@ -1148,5 +1148,6 @@
     "notReplyToFloorTip": "不回覆該樓層（改為回覆樓主）",
     "expandToolbarTip": "展開工具列",
     "collapseToolbarTip": "收起工具列"
-  }
+  },
+  "workaroundRedirect": "查看對話"
 }

lib/utils/html/html_muncher.dart

@@ -4,9 +4,11 @@ import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:tsdm_client/constants/constants.dart';
 import 'package:tsdm_client/constants/layout.dart';
+import 'package:tsdm_client/constants/url.dart';
 import 'package:tsdm_client/extensions/build_context.dart';
 import 'package:tsdm_client/extensions/string.dart';
 import 'package:tsdm_client/extensions/universal_html.dart';
+import 'package:tsdm_client/i18n/strings.g.dart';
 import 'package:tsdm_client/shared/models/models.dart';
 import 'package:tsdm_client/utils/html/adaptive_color.dart';
 import 'package:tsdm_client/utils/html/css_parser.dart';
@@ -384,6 +386,23 @@ final class _Muncher with LoggerMixin {
     final hrefUrl = state.tapUrl;
     final imgWidth = element.attributes['width']?.parseToInt()?.toDouble();
     final imgHeight = element.attributes['height']?.parseToInt()?.toDouble();
+
+    // Show a button instead of the original image.
+    if (tmpImpellerWorkaroundUrls.contains(url)) {
+      return [
+        WidgetSpan(
+          child: IconButton(
+            icon: Icon(Icons.navigate_before_outlined, color: Theme.of(context).colorScheme.tertiary),
+            // Constrains size to fit line height.
+            constraints: const BoxConstraints(maxWidth: 24, minWidth: 24, maxHeight: 24, minHeight: 24),
+            padding: EdgeInsets.zero,
+            tooltip: context.t.workaroundRedirect,
+            onPressed: hrefUrl != null ? () async => context.dispatchAsUrl(hrefUrl) : null,
+          ),
+        ),
+      ];
+    }
+
     return [
       WidgetSpan(
         child: GestureDetector(

lib/widgets/cached_image/cached_image.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:shimmer/shimmer.dart';
 import 'package:tsdm_client/constants/layout.dart';
+import 'package:tsdm_client/constants/url.dart';
 import 'package:tsdm_client/extensions/color.dart';
 import 'package:tsdm_client/features/cache/models/models.dart';
 import 'package:tsdm_client/instance.dart';
@@ -94,6 +95,9 @@ class _CachedImageState extends State<CachedImage> with LoggerMixin {
   @override
   void initState() {
     super.initState();
+    if (tmpImpellerWorkaroundUrls.contains(widget.imageUrl)) {
+      return;
+    }
     imageSub = getIt
         .get<ImageCacheProvider>()
         .response
@@ -109,6 +113,11 @@ class _CachedImageState extends State<CachedImage> with LoggerMixin {
 
   @override
   Widget build(BuildContext context) {
+    // Show an icon instead of the original image.
+    if (tmpImpellerWorkaroundUrls.contains(widget.imageUrl)) {
+      return Icon(Icons.navigate_before_outlined, color: Theme.of(context).colorScheme.tertiary);
+    }
+
     final Widget body;
     if (widget.imageUrl.isEmpty) {
       body = FallbackPicture(