perf(mobile): avoid reparsing unchanged Markdown

mobile/lib/features/channels/message_content.dart

@@ -3,6 +3,7 @@ import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
@@ -33,6 +34,7 @@ import 'message_media.dart';
 import 'voice_note_attachment.dart';
 
 part 'message_content/media_carousel.dart';
+part 'message_content/inline_components.dart';
 part 'message_content/token_pill.dart';
 part 'message_content/video_preview.dart';
 
@@ -176,13 +178,33 @@ class MessageContent extends HookConsumerWidget {
                 in ref.watch(channelsProvider).asData?.value ?? const [])
               channel.name.toLowerCase(): channel.id,
           };
-    final resolvedChannelTap =
-        onChannelTap ??
-        (String channelId) {
+    final channelHandler = useRef(onChannelTap)..value = onChannelTap;
+    final resolvedChannelTap = useMemoized(
+      () => (String channelId) {
+        final handler = channelHandler.value;
+        if (handler != null) {
+          handler(channelId);
+        } else {
           ref
               .read(pendingDeepLinkProvider.notifier)
               .open(Uri(scheme: 'buzz', host: 'channel', path: channelId));
-        };
+        }
+      },
+      const [],
+    );
+    final replyHandler = useRef(onMediaReply)..value = onMediaReply;
+    final moreHandler = useRef(onMediaMore)..value = onMediaMore;
+    final mediaReply = useMemoized(
+      () =>
+          () => replyHandler.value?.call(),
+      const [],
+    );
+    final mediaMore = useMemoized(
+      () =>
+          (BuildContext context, String url) =>
+              moreHandler.value?.call(context, url),
+      const [],
+    );
     final channelPresentationKey = [
       for (final entry
           in (resolvedChannelNames.entries.toList()
@@ -265,7 +287,23 @@ class MessageContent extends HookConsumerWidget {
         result = '\u200B$result';
       }
       return result;
-    }, [linkNormalizedContent, resolvedMentionNames]);
+    }, [linkNormalizedContent, mentionPresentationKey]);
+
+    final inlineComponents = _useMessageInlineComponents(
+      content: content,
+      finalContent: finalContent,
+      mentionNames: resolvedMentionNames,
+      bindings: mentionBindings,
+      agentPubkeys: resolvedAgentMentionPubkeys,
+      channelNames: resolvedChannelNames,
+      customEmoji: customEmoji,
+      emojiSize: inlineCustomEmojiSize,
+      tags: tags,
+      hasMediaReply: onMediaReply != null,
+      hasMediaMore: onMediaMore != null,
+      onMentionTap: onMentionTap,
+      onChannelTap: resolvedChannelTap,
+    );
 
     final markdown = KeyedSubtree(
       key: ValueKey(
@@ -291,35 +329,16 @@ class MessageContent extends HookConsumerWidget {
           resolvedChannelTap,
           resolvedChannelNames,
         ),
-        imageBuilder: (context, imageUrl, _, _) =>
-            _buildMedia(context, imageUrl, imetaByUrl[imageUrl]),
+        imageBuilder: (context, imageUrl, _, _) => _buildMedia(
+          context,
+          imageUrl,
+          imetaByUrl[imageUrl],
+          onReply: onMediaReply == null ? null : mediaReply,
+          onMore: onMediaMore == null ? null : mediaMore,
+        ),
         textAlign: textAlign,
         maxLines: maxLines,
-        inlineComponents: [
-          _MentionMd(
-            mentionNames: resolvedMentionNames,
-            bindings: mentionBindings,
-            displayLabels: {
-              for (final range in mentionOccurrences(
-                content,
-                mentionBindings.keys,
-              ))
-                range.label: content.substring(range.start + 1, range.end),
-            },
-            agentMentionPubkeys: resolvedAgentMentionPubkeys,
-            onMentionTap: onMentionTap,
-          ),
-          CustomEmojiMd(
-            customEmoji,
-            content: finalContent,
-            size: inlineCustomEmojiSize,
-          ),
-          _ChannelLinkMd(
-            channelNames: resolvedChannelNames,
-            onChannelTap: resolvedChannelTap,
-          ),
-          ...MarkdownComponent.inlineComponents,
-        ],
+        inlineComponents: inlineComponents,
       ),
     );
     if (trailingGallery == null) return markdown;
@@ -343,7 +362,13 @@ class MessageContent extends HookConsumerWidget {
     );
   }
 
-  Widget _buildMedia(BuildContext context, String imageUrl, ImetaEntry? imeta) {
+  Widget _buildMedia(
+    BuildContext context,
+    String imageUrl,
+    ImetaEntry? imeta, {
+    VoidCallback? onReply,
+    MediaViewerMoreAction? onMore,
+  }) {
     final mediaKind = classifyMediaUrl(imageUrl, imeta: imeta);
     if (mediaKind == MessageMediaKind.audio) {
       return Padding(
@@ -360,15 +385,15 @@ class MessageContent extends HookConsumerWidget {
       return _MessageVideoPreview(
         url: imageUrl,
         imeta: imeta,
-        onReply: onMediaReply,
+        onReply: onReply,
       );
     }
     return _MessageImagePreview(
       url: imageUrl,
       imeta: imeta,
       semanticLabel: imeta?.alt ?? 'Message image',
-      onReply: onMediaReply,
-      onMore: onMediaMore,
+      onReply: onReply,
+      onMore: onMore,
     );
   }
 

mobile/lib/features/channels/message_content/inline_components.dart

@@ -0,0 +1,136 @@
+part of '../message_content.dart';
+
+List<MarkdownComponent> _useMessageInlineComponents({
+  required String content,
+  required String finalContent,
+  required Map<String, String> mentionNames,
+  required Map<String, Set<String>> bindings,
+  required Set<String> agentPubkeys,
+  required Map<String, String> channelNames,
+  required List<CustomEmoji> customEmoji,
+  required double emojiSize,
+  required List<List<String>> tags,
+  required bool hasMediaReply,
+  required bool hasMediaMore,
+  required void Function(String)? onMentionTap,
+  required void Function(String) onChannelTap,
+}) {
+  // Parsed spans retain these callbacks. Forward to the current handlers without
+  // invalidating the parser for a new closure from an otherwise unchanged row.
+  final mentionHandler = useRef(onMentionTap)..value = onMentionTap;
+  final channelHandler = useRef(onChannelTap)..value = onChannelTap;
+  final mentionTap = useMemoized(
+    () =>
+        (String pubkey) => mentionHandler.value?.call(pubkey),
+    const [],
+  );
+  final channelTap = useMemoized(
+    () =>
+        (String channelId) => channelHandler.value(channelId),
+    const [],
+  );
+  final inputs = _InlineComponentInputs(
+    content: content,
+    finalContent: finalContent,
+    mentionNames: mentionNames,
+    bindings: bindings,
+    agentPubkeys: agentPubkeys,
+    channelNames: channelNames,
+    customEmoji: customEmoji,
+    emojiSize: emojiSize,
+    tags: tags,
+    hasMediaReply: hasMediaReply,
+    hasMediaMore: hasMediaMore,
+    hasMentionHandler: onMentionTap != null,
+  );
+
+  // gpt_markdown compares components by identity. Recreating them on every
+  // parent rebuild reparses unchanged message bodies on the UI isolate.
+  return useMemoized(
+    () => [
+      _MentionMd(
+        mentionNames: inputs.mentionNames,
+        bindings: inputs.bindings,
+        displayLabels: {
+          for (final range in mentionOccurrences(content, bindings.keys))
+            range.label: content.substring(range.start + 1, range.end),
+        },
+        agentMentionPubkeys: inputs.agentPubkeys,
+        onMentionTap: inputs.hasMentionHandler ? mentionTap : null,
+      ),
+      CustomEmojiMd(inputs.customEmoji, content: finalContent, size: emojiSize),
+      _ChannelLinkMd(
+        channelNames: inputs.channelNames,
+        onChannelTap: channelTap,
+      ),
+      ...MarkdownComponent.inlineComponents,
+    ],
+    [inputs],
+  );
+}
+
+class _InlineComponentInputs {
+  final String content;
+  final String finalContent;
+  final Map<String, String> mentionNames;
+  final Map<String, Set<String>> bindings;
+  final Set<String> agentPubkeys;
+  final Map<String, String> channelNames;
+  final List<CustomEmoji> customEmoji;
+  final double emojiSize;
+  final bool hasMentionHandler;
+  final List<List<String>> tags;
+  final bool hasMediaReply;
+  final bool hasMediaMore;
+
+  _InlineComponentInputs({
+    required this.content,
+    required this.finalContent,
+    required Map<String, String> mentionNames,
+    required Map<String, Set<String>> bindings,
+    required Set<String> agentPubkeys,
+    required Map<String, String> channelNames,
+    required List<CustomEmoji> customEmoji,
+    required this.emojiSize,
+    required this.hasMentionHandler,
+    required List<List<String>> tags,
+    required this.hasMediaReply,
+    required this.hasMediaMore,
+  }) : tags = List.unmodifiable(
+         tags.map((tag) => List<String>.unmodifiable(tag)),
+       ),
+       mentionNames = Map.unmodifiable(mentionNames),
+       bindings = Map.unmodifiable({
+         for (final entry in bindings.entries)
+           entry.key: Set<String>.unmodifiable(entry.value),
+       }),
+       agentPubkeys = Set.unmodifiable(agentPubkeys),
+       channelNames = Map.unmodifiable(channelNames),
+       customEmoji = List.unmodifiable(customEmoji);
+
+  @override
+  bool operator ==(Object other) =>
+      other is _InlineComponentInputs &&
+      content == other.content &&
+      finalContent == other.finalContent &&
+      emojiSize == other.emojiSize &&
+      hasMentionHandler == other.hasMentionHandler &&
+      hasMediaReply == other.hasMediaReply &&
+      hasMediaMore == other.hasMediaMore &&
+      tags.length == other.tags.length &&
+      tags.indexed.every(
+        (entry) => listEquals(entry.$2, other.tags[entry.$1]),
+      ) &&
+      mapEquals(mentionNames, other.mentionNames) &&
+      mapEquals(channelNames, other.channelNames) &&
+      setEquals(agentPubkeys, other.agentPubkeys) &&
+      listEquals(customEmoji, other.customEmoji) &&
+      bindings.length == other.bindings.length &&
+      bindings.entries.every(
+        (entry) => setEquals(entry.value, other.bindings[entry.key]),
+      );
+
+  @override
+  int get hashCode =>
+      Object.hash(content, finalContent, emojiSize, hasMentionHandler);
+}