feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/shared/emoji/emoji_burst.dart

@@ -0,0 +1,398 @@
+/// Emoji particle bursts, ported from desktop's `EmojiBurstProvider`
+/// (`desktop/src/shared/ui/EmojiBurstProvider.tsx`).
+///
+/// Desktop paints to a fixed full-window `<canvas>` above everything and steps
+/// the particles on `requestAnimationFrame`. Mobile does the same shape:
+/// [EmojiBurstOverlay] installs one full-screen [CustomPaint] above the
+/// navigator (so bursts survive route pushes and modal sheets), and a [Ticker]
+/// steps the same physics.
+///
+/// The constants below are desktop's, unchanged — the motion is the product
+/// decision, and drifting it would make the two clients feel different.
+library;
+
+import 'dart:math';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+
+import 'positive_emoji.dart';
+
+/// Particles per burst — desktop's `PICKER_PARTICLES_PER_BURST`.
+const _particlesPerBurst = 5;
+
+/// Frames a particle lives — desktop's `PICKER_PARTICLE_LIFE_FRAMES`.
+const _particleLifeFrames = 108;
+
+/// Desktop's `MAX_ACTIVE`, scaled down: a phone screen holds far fewer
+/// particles before it reads as noise, and every one costs a `saveLayer`.
+const _maxActiveParticles = 160;
+
+/// Physics runs at a fixed 60Hz step regardless of display refresh rate.
+/// Desktop's constants are per-frame deltas on a 60Hz assumption; stepping them
+/// once per real frame would run the burst at double speed on a 120Hz panel.
+const _stepSeconds = 1 / 60;
+
+/// Cap on catch-up steps per frame so a stalled frame can't spiral.
+const _maxStepsPerFrame = 4;
+
+/// Glyph size the cached [TextPainter] is laid out at. Particles scale off this
+/// rather than re-laying out text every frame.
+const _glyphCachePx = 64.0;
+
+/// The last emoji added as a reaction that is still waiting for its pill to
+/// appear on screen.
+///
+/// Mobile reactions are not optimistic — `addReaction` awaits the relay and the
+/// pill only exists once the event echoes back — so a burst fired at pick time
+/// would play against a row that has not changed yet. Desktop solves this the
+/// same way (`burstEmojiOnRender` in `MessageReactions.tsx`): remember the
+/// pending emoji, and let the pill fire the burst from its own position the
+/// frame it first renders as reacted-by-me.
+@immutable
+class PendingReactionBurst {
+  final String messageId;
+  final String emoji;
+
+  const PendingReactionBurst({required this.messageId, required this.emoji});
+
+  @override
+  bool operator ==(Object other) =>
+      other is PendingReactionBurst &&
+      other.messageId == messageId &&
+      other.emoji == emoji;
+
+  @override
+  int get hashCode => Object.hash(messageId, emoji);
+}
+
+/// One slot, not a queue: a burst is a flourish on the reaction you just added,
+/// and two adds in flight at once means the newer one is the interesting one.
+class PendingReactionBurstNotifier extends Notifier<PendingReactionBurst?> {
+  @override
+  PendingReactionBurst? build() => null;
+
+  /// Arm a burst for [emoji] on [messageId]. No-op for emoji that don't
+  /// celebrate, so callers don't have to gate themselves.
+  void arm(String messageId, String emoji) {
+    if (!isPositiveEmojiParticle(emoji)) return;
+    state = PendingReactionBurst(messageId: messageId, emoji: emoji);
+  }
+
+  /// Claim the pending burst if it is [target], returning whether the caller
+  /// won. The same message can be on screen twice (a thread pushed over its
+  /// channel), so exactly one pill must fire.
+  bool claim(PendingReactionBurst target) {
+    if (state != target) return false;
+    state = null;
+    return true;
+  }
+}
+
+final pendingReactionBurstProvider =
+    NotifierProvider<PendingReactionBurstNotifier, PendingReactionBurst?>(
+      PendingReactionBurstNotifier.new,
+    );
+
+class _Particle {
+  double x;
+  double y;
+  double xv;
+  double yv;
+  double rotation;
+  double spin;
+  double scale;
+  double opacity;
+  double life;
+  final double maxLife;
+  final String emoji;
+  final double fontSize;
+  final double gravity;
+
+  _Particle({
+    required this.x,
+    required this.y,
+    required this.xv,
+    required this.yv,
+    required this.rotation,
+    required this.spin,
+    required this.scale,
+    required this.opacity,
+    required this.life,
+    required this.maxLife,
+    required this.emoji,
+    required this.fontSize,
+    required this.gravity,
+  });
+
+  /// Desktop's `updateParticle`. Returns false once the particle is spent.
+  bool step() {
+    life -= 1;
+    rotation += spin;
+    yv += gravity;
+    xv *= 0.965;
+    yv *= 0.998;
+    x += xv;
+    y += yv;
+    scale += (1 - scale) * 0.28;
+
+    final lifeRatio = life / maxLife;
+    if (lifeRatio < 0.24) {
+      opacity = max(0, lifeRatio / 0.24);
+    }
+
+    return life > 0 && opacity > 0.02;
+  }
+}
+
+/// Holds the live particles and notifies the painter each step.
+///
+/// Deliberately not a `Notifier` over a particle list: the particles mutate 60
+/// times a second and must never rebuild a widget. Listeners are the painter's
+/// repaint signal only.
+class EmojiBurstController extends ChangeNotifier {
+  final List<_Particle> _particles = [];
+  final Random _random;
+
+  /// Set when a spawn arrives so the overlay knows to start its ticker.
+  VoidCallback? onSpawn;
+
+  EmojiBurstController({Random? random}) : _random = random ?? Random();
+
+  bool get hasParticles => _particles.isNotEmpty;
+
+  /// Spawn a burst of [emoji] centred on [origin] (global coordinates).
+  /// Mirrors desktop's `spawnPickerEmojiBurst`.
+  void burst(String emoji, Offset origin) {
+    final trimmed = emoji.trim();
+    if (trimmed.isEmpty) return;
+    if (_particles.length + _particlesPerBurst > _maxActiveParticles) return;
+
+    for (var i = 0; i < _particlesPerBurst; i += 1) {
+      final horizontalDrift = (_random.nextDouble() - 0.5) * 4.4;
+      final initialLift = 2.1 + _random.nextDouble() * 2.35;
+
+      _particles.add(
+        _Particle(
+          x: origin.dx,
+          y: origin.dy,
+          xv: horizontalDrift,
+          yv: -initialLift,
+          rotation: (_random.nextDouble() - 0.5) * 22,
+          spin: (_random.nextDouble() - 0.5) * 5.2,
+          scale: 0.25,
+          opacity: 1,
+          life: _particleLifeFrames.toDouble(),
+          maxLife: _particleLifeFrames.toDouble(),
+          emoji: trimmed,
+          fontSize: 18 + (_random.nextDouble() * 24).ceilToDouble(),
+          // Negative: the burst floats up and keeps accelerating upward.
+          gravity: -(0.018 + _random.nextDouble() * 0.018),
+        ),
+      );
+    }
+
+    onSpawn?.call();
+    notifyListeners();
+  }
+
+  /// Advance one fixed step. Returns whether any particles remain.
+  bool step() {
+    for (var i = _particles.length - 1; i >= 0; i -= 1) {
+      if (!_particles[i].step()) {
+        _particles[i] = _particles.last;
+        _particles.removeLast();
+      }
+    }
+    notifyListeners();
+    return _particles.isNotEmpty;
+  }
+
+  void clear() {
+    if (_particles.isEmpty) return;
+    _particles.clear();
+    notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    _particles.clear();
+    super.dispose();
+  }
+}
+
+final emojiBurstControllerProvider = Provider<EmojiBurstController>((ref) {
+  final controller = EmojiBurstController();
+  ref.onDispose(controller.dispose);
+  return controller;
+});
+
+/// Fire a burst of [emoji] centred on [context]'s own box.
+///
+/// The convenience the call sites actually want: they have a build context for
+/// the pill or tile that was tapped and no reason to know about global
+/// coordinates. Silently does nothing for emoji outside the positive set or
+/// when the platform asks for reduced motion, so callers stay simple.
+void burstEmojiFromContext(
+  WidgetRef ref,
+  BuildContext context,
+  String emoji, {
+  bool requirePositive = true,
+}) {
+  if (requirePositive && !isPositiveEmojiParticle(emoji)) return;
+  if (MediaQuery.maybeDisableAnimationsOf(context) ?? false) return;
+
+  final box = context.findRenderObject();
+  if (box is! RenderBox || !box.hasSize) return;
+  final origin = box.localToGlobal(box.size.center(Offset.zero));
+  ref.read(emojiBurstControllerProvider).burst(emoji, origin);
+}
+
+/// Full-screen particle layer. Install once, above the navigator, so bursts
+/// keep playing over pushed routes and modal sheets.
+class EmojiBurstOverlay extends HookConsumerWidget {
+  final Widget child;
+
+  const EmojiBurstOverlay({super.key, required this.child});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final controller = ref.watch(emojiBurstControllerProvider);
+    final tickerProvider = useSingleTickerProvider();
+
+    // Ticker + leftover time live in refs: stepping physics must not rebuild
+    // this widget, which wraps the entire app.
+    final leftover = useRef(0.0);
+    final lastElapsed = useRef(Duration.zero);
+
+    final ticker = useMemoized(() {
+      late final Ticker created;
+      created = tickerProvider.createTicker((elapsed) {
+        final delta = elapsed - lastElapsed.value;
+        lastElapsed.value = elapsed;
+        leftover.value += delta.inMicroseconds / Duration.microsecondsPerSecond;
+
+        var steps = 0;
+        var alive = controller.hasParticles;
+        while (leftover.value >= _stepSeconds && steps < _maxStepsPerFrame) {
+          leftover.value -= _stepSeconds;
+          steps += 1;
+          alive = controller.step();
+          if (!alive) break;
+        }
+        // Don't bank unspent time from a stall — it would fast-forward the
+        // next burst.
+        if (steps >= _maxStepsPerFrame) leftover.value = 0;
+
+        if (!alive) {
+          created.stop();
+          lastElapsed.value = Duration.zero;
+          leftover.value = 0;
+        }
+      });
+      return created;
+    }, [tickerProvider, controller]);
+
+    useEffect(() => ticker.dispose, [ticker]);
+
+    useEffect(() {
+      void start() {
+        if (ticker.isActive) return;
+        lastElapsed.value = Duration.zero;
+        leftover.value = 0;
+        ticker.start();
+      }
+
+      controller.onSpawn = start;
+      if (controller.hasParticles) start();
+      return () {
+        if (controller.onSpawn == start) controller.onSpawn = null;
+      };
+    }, [ticker, controller]);
+
+    return Stack(
+      children: [
+        child,
+        Positioned.fill(
+          child: IgnorePointer(
+            child: ExcludeSemantics(
+              child: RepaintBoundary(
+                child: CustomPaint(painter: _EmojiBurstPainter(controller)),
+              ),
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}
+
+/// Laid-out glyphs, keyed by emoji. Emoji are drawn thousands of times per
+/// burst; laying out the text once and scaling the canvas is the whole trick.
+final Map<String, TextPainter> _glyphCache = {};
+
+/// Bounded so a chatty channel full of distinct reactions can't grow it
+/// without limit. Bursts are visual sugar — evicting the whole cache costs one
+/// re-layout per emoji still on screen.
+const _glyphCacheLimit = 64;
+
+TextPainter _glyphFor(String emoji) {
+  final cached = _glyphCache[emoji];
+  if (cached != null) return cached;
+  if (_glyphCache.length >= _glyphCacheLimit) _glyphCache.clear();
+
+  final painter = TextPainter(
+    text: TextSpan(
+      text: emoji,
+      style: const TextStyle(fontSize: _glyphCachePx),
+    ),
+    textDirection: TextDirection.ltr,
+  )..layout();
+  _glyphCache[emoji] = painter;
+  return painter;
+}
+
+/// Drop the cached glyph layouts. Exposed for tests; the cache is not
+/// community- or account-scoped, so nothing else needs to reset it.
+@visibleForTesting
+void clearEmojiBurstGlyphCache() => _glyphCache.clear();
+
+class _EmojiBurstPainter extends CustomPainter {
+  final EmojiBurstController controller;
+
+  _EmojiBurstPainter(this.controller) : super(repaint: controller);
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    for (final particle in controller._particles) {
+      final glyph = _glyphFor(particle.emoji);
+      final drawSize = particle.fontSize * particle.scale;
+      final scale = drawSize / _glyphCachePx;
+
+      canvas.save();
+      canvas.translate(particle.x, particle.y);
+      canvas.rotate(particle.rotation * pi / 180);
+      canvas.scale(scale);
+      // Color fonts ignore TextStyle.color, so fade through a layer instead.
+      if (particle.opacity < 1) {
+        canvas.saveLayer(
+          Rect.fromCenter(
+            center: Offset.zero,
+            width: glyph.width,
+            height: glyph.height,
+          ),
+          Paint()..color = Colors.black.withValues(alpha: particle.opacity),
+        );
+      }
+      glyph.paint(canvas, Offset(-glyph.width / 2, -glyph.height / 2));
+      if (particle.opacity < 1) canvas.restore();
+      canvas.restore();
+    }
+  }
+
+  @override
+  bool shouldRepaint(_EmojiBurstPainter oldDelegate) =>
+      oldDelegate.controller != controller;
+}

mobile/lib/shared/emoji/emoji_data.dart

@@ -0,0 +1,154 @@
+import 'package:flutter/foundation.dart';
+
+/// The standard (Unicode) emoji set, projected from the same emoji-mart dataset
+/// desktop uses.
+///
+/// The asset at `assets/emoji/emoji-data.json` is generated by
+/// `just mobile-emoji-data`; ids here are emoji-mart ids, which are exactly the
+/// `:shortcode:` values desktop emits from its picker and resolves in
+/// `emojiDisplayName`. Keeping both clients on one dataset is what stops a
+/// shortcode from meaning different things on mobile and desktop.
+@immutable
+class EmojiEntry {
+  /// emoji-mart id, i.e. the shortcode without the surrounding colons.
+  final String id;
+
+  /// Human-readable name, e.g. `Index Pointing Up`.
+  final String name;
+
+  /// Search keywords from the dataset.
+  final List<String> keywords;
+
+  /// The default-skin glyph.
+  final String native;
+
+  /// Position within emoji-mart's skin list. The default skin is zero.
+  final int skinIndex;
+
+  /// Owning category id, e.g. `people`.
+  final String categoryId;
+
+  const EmojiEntry({
+    required this.id,
+    required this.name,
+    required this.keywords,
+    required this.native,
+    required this.categoryId,
+    this.skinIndex = 0,
+  });
+
+  /// Unique tile id while preserving the desktop-identical shortcode for the
+  /// default skin.
+  String get tileId => skinIndex == 0 ? id : '$id-$skinIndex';
+}
+
+/// One dataset category, in emoji-mart's own order.
+@immutable
+class EmojiCategory {
+  final String id;
+  final List<EmojiEntry> emoji;
+
+  const EmojiCategory({required this.id, required this.emoji});
+
+  /// Title-cased label for the category rail.
+  String get label => switch (id) {
+    'people' => 'Smileys & People',
+    'nature' => 'Animals & Nature',
+    'foods' => 'Food & Drink',
+    'activity' => 'Activity',
+    'places' => 'Travel & Places',
+    'objects' => 'Objects',
+    'symbols' => 'Symbols',
+    'flags' => 'Flags',
+    _ => id,
+  };
+}
+
+/// Parsed emoji dataset: ordered categories, a flat list for search, and a
+/// reverse glyph index for resolving a reaction back to its shortcode.
+@immutable
+class EmojiDataset {
+  final List<EmojiCategory> categories;
+
+  /// Every entry, in category order. Search scans this.
+  final List<EmojiEntry> all;
+
+  /// Glyph to `:shortcode:`. Mirrors desktop's `emojiDisplayName`.
+  final Map<String, String> nativeToShortcode;
+
+  const EmojiDataset({
+    required this.categories,
+    required this.all,
+    required this.nativeToShortcode,
+  });
+
+  static const empty = EmojiDataset(
+    categories: [],
+    all: [],
+    nativeToShortcode: {},
+  );
+
+  bool get isEmpty => all.isEmpty;
+
+  /// Resolve a reaction value to something displayable as a name: a custom
+  /// emoji's `:shortcode:` passes through, a Unicode glyph maps to its
+  /// shortcode, and anything unknown falls back to itself.
+  String displayName(String emoji) {
+    final trimmed = emoji.trim();
+    if (trimmed.startsWith(':') && trimmed.endsWith(':')) return trimmed;
+    return nativeToShortcode[trimmed] ?? trimmed;
+  }
+
+  /// Parse the generated asset. Runs on a background isolate via `compute`, so
+  /// it must stay a top-level-callable pure function over plain JSON.
+  static EmojiDataset fromJson(Map<String, dynamic> json) {
+    final rawEmoji = (json['emoji'] as Map).cast<String, dynamic>();
+    final rawCategories = (json['categories'] as List).cast<dynamic>();
+
+    final categories = <EmojiCategory>[];
+    final all = <EmojiEntry>[];
+    final nativeToShortcode = <String, String>{};
+
+    for (final rawCategory in rawCategories) {
+      final category = (rawCategory as Map).cast<String, dynamic>();
+      final categoryId = category['id'] as String;
+      final entries = <EmojiEntry>[];
+
+      for (final rawId in (category['emoji'] as List).cast<dynamic>()) {
+        final id = rawId as String;
+        final record = (rawEmoji[id] as Map?)?.cast<String, dynamic>();
+        if (record == null) continue;
+        // Older committed assets used one string; accept that shape so the
+        // parser remains safe while generated assets move to all skin variants.
+        final natives = switch (record['u']) {
+          final List values => values.cast<String>(),
+          final String value => [value],
+          _ => const <String>[],
+        };
+        for (final (skinIndex, native) in natives.indexed) {
+          final entry = EmojiEntry(
+            id: id,
+            name: record['n'] as String,
+            keywords: (record['k'] as List).cast<String>(),
+            native: native,
+            categoryId: categoryId,
+            skinIndex: skinIndex,
+          );
+          entries.add(entry);
+          all.add(entry);
+          // First writer wins so the earliest category owns a shared glyph,
+          // matching desktop's map build order.
+          nativeToShortcode.putIfAbsent(entry.native, () => ':$id:');
+        }
+      }
+
+      categories.add(EmojiCategory(id: categoryId, emoji: entries));
+    }
+
+    return EmojiDataset(
+      categories: categories,
+      all: all,
+      nativeToShortcode: nativeToShortcode,
+    );
+  }
+}

mobile/lib/shared/emoji/emoji_data_provider.dart

@@ -0,0 +1,38 @@
+import 'dart:convert';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart' show rootBundle;
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+
+import 'emoji_data.dart';
+
+/// Asset path for the generated dataset. See `mobile/scripts/generate-emoji-data.mjs`.
+const emojiDataAssetPath = 'assets/emoji/emoji-data.json';
+
+/// Decode + parse off the UI isolate. ~1.9k entries is fast but not free, and
+/// the picker sheet animates in while this runs.
+EmojiDataset _parseEmojiData(String source) {
+  return EmojiDataset.fromJson(jsonDecode(source) as Map<String, dynamic>);
+}
+
+/// The standard emoji dataset, loaded once from the app bundle.
+final emojiDatasetProvider = FutureProvider<EmojiDataset>((ref) async {
+  final source = await rootBundle.loadString(emojiDataAssetPath);
+  return compute(_parseEmojiData, source);
+});
+
+/// Synchronous read of the dataset — [EmojiDataset.empty] while loading or on
+/// error. Convenience for widgets that only need the resolved value, mirroring
+/// `customEmojiListProvider`.
+final emojiDatasetOrEmptyProvider = Provider<EmojiDataset>((ref) {
+  return ref.watch(emojiDatasetProvider).value ?? EmojiDataset.empty;
+});
+
+/// Every glyph in the dataset, as a set for membership tests.
+///
+/// Built once per dataset load rather than per message: `isEmojiOnlyMessage`
+/// runs on every rendered body, and materializing ~1.9k keys there would be a
+/// per-frame cost.
+final nativeEmojiGlyphsProvider = Provider<Set<String>>((ref) {
+  return ref.watch(emojiDatasetOrEmptyProvider).nativeToShortcode.keys.toSet();
+});

mobile/lib/shared/emoji/emoji_only.dart

@@ -0,0 +1,87 @@
+/// Detection and sizing for messages whose entire body is emoji, ported from
+/// desktop's `isEmojiOnlyMessage` (`desktop/src/shared/lib/emojiOnly.ts`) and
+/// the `emojiOnly` branch of `MessageRow.tsx`.
+library;
+
+import 'package:characters/characters.dart';
+
+import '../custom_emoji/custom_emoji.dart';
+
+/// Body size for an emoji-only message. Desktop steps `text-sm` (14px) up to
+/// `text-4xl`; mobile body text is the same 14px, so the same 36px lands the
+/// same jump.
+const double kEmojiOnlyFontSize = 36.0;
+
+/// Line height for an emoji-only body — desktop's `leading-tight`. Emoji have
+/// generous internal leading already, so normal line spacing leaves a gap that
+/// reads as a blank row.
+const double kEmojiOnlyHeight = 1.25;
+
+/// Inline custom-emoji size inside an emoji-only message. Desktop sizes these
+/// at `1.45em` of the surrounding text.
+const double kEmojiOnlyCustomEmojiSize = kEmojiOnlyFontSize * 1.45;
+
+/// Anything with `Extended_Pictographic` in it is emoji enough. Keycaps and
+/// digit-based sequences don't match — those are covered by the dataset's own
+/// native set instead, exactly as desktop does it.
+final RegExp _pictographic = RegExp(
+  r'\p{Extended_Pictographic}',
+  unicode: true,
+);
+
+/// Whether [content] is nothing but emoji — native glyphs, known custom
+/// `:shortcode:`s, and whitespace, with at least one emoji present.
+///
+/// [nativeEmoji] is the dataset's glyph set — read `nativeEmojiGlyphsProvider`.
+/// Passing an empty set still gives correct results for ordinary emoji, since
+/// the pictographic check stands on its own; only glyphs with no pictographic
+/// code point of their own (keycaps like 1️⃣) need the set.
+bool isEmojiOnlyMessage(
+  String content, {
+  required Set<String> nativeEmoji,
+  List<CustomEmoji> customEmoji = const [],
+}) {
+  final trimmed = content.trim();
+  if (trimmed.isEmpty) return false;
+
+  final shortcodes = {
+    for (final emoji in customEmoji) emoji.shortcode.toLowerCase(),
+  };
+  var sawEmoji = false;
+
+  // Grapheme clusters, so a ZWJ family or a flag pair is one unit. Desktop
+  // hand-rolls this scan; Dart's `characters` already segments correctly.
+  final iterator = trimmed.characters.iterator;
+  final clusters = <String>[];
+  while (iterator.moveNext()) {
+    clusters.add(iterator.current);
+  }
+
+  var index = 0;
+  while (index < clusters.length) {
+    final cluster = clusters[index];
+
+    if (cluster.trim().isEmpty) {
+      index += 1;
+      continue;
+    }
+
+    if (cluster == ':') {
+      final end = clusters.indexOf(':', index + 1);
+      if (end <= index + 1) return false;
+      final shortcode = clusters.sublist(index + 1, end).join().toLowerCase();
+      if (!shortcodes.contains(shortcode)) return false;
+      sawEmoji = true;
+      index = end + 1;
+      continue;
+    }
+
+    if (!nativeEmoji.contains(cluster) && !_pictographic.hasMatch(cluster)) {
+      return false;
+    }
+    sawEmoji = true;
+    index += 1;
+  }
+
+  return sawEmoji;
+}

mobile/lib/shared/emoji/emoji_search.dart

@@ -0,0 +1,214 @@
+/// Emoji search for the mobile picker and reaction tray.
+///
+/// Ported from `desktop/src/shared/lib/emojiSearch.ts`, which exists because
+/// emoji-mart's own search is token-prefix based and so can't cross the `_` in
+/// a shortcode — `pointup` never finds `point_up`. The tiers keep ordinary
+/// queries ranked the way you'd expect while still surfacing looser matches
+/// last: exact > prefix > substring > subsequence over the shortcode.
+///
+/// Mobile extends the desktop tiers with name/keyword matching, because the
+/// tray replaces emoji-mart's picker (which searched names and keywords) rather
+/// than just its `:shortcode` autocomplete. Shortcode hits still outrank
+/// keyword hits, so typing a shortcode you know never buries it.
+library;
+
+import 'emoji_data.dart';
+
+// Lower tier = stronger match.
+const _tierExact = 0;
+const _tierShortcodePrefix = 1;
+const _tierKeywordPrefix = 2;
+const _tierShortcodeSubstring = 3;
+const _tierKeywordSubstring = 4;
+const _tierSubsequence = 5;
+
+/// Sentinel ranking worse than every real tier.
+const _noMatch = 1 << 20;
+
+final _separators = RegExp(r'[:_\s-]');
+final _wordSplit = RegExp(r'[\s_-]+');
+
+/// Lowercase and drop separators (`:`, `_`, `-`, whitespace) so matching is
+/// insensitive to shortcode punctuation. `point_up` and `pointup` collapse to
+/// the same normalized form.
+///
+/// Named for what it does rather than desktop's `normalizeShortcode`, because
+/// `custom_emoji.dart` already exports a validating `normalizeShortcode` with
+/// different semantics (it returns null for malformed input).
+String collapseSeparators(String value) {
+  return value.toLowerCase().replaceAll(_separators, '');
+}
+
+/// A ranked match. [score] is a within-tier tiebreak — lower is better.
+class EmojiMatch {
+  final int tier;
+  final int score;
+
+  const EmojiMatch({required this.tier, required this.score});
+}
+
+/// If [query] is a subsequence of [target] (all chars in order, gaps allowed),
+/// return the span of the match as a tightness score — smaller is tighter.
+/// Returns null when it isn't a subsequence.
+int? _subsequenceSpan(String query, String target) {
+  var first = -1;
+  var last = -1;
+  var qi = 0;
+  for (var ti = 0; ti < target.length && qi < query.length; ti++) {
+    if (target[ti] == query[qi]) {
+      if (first == -1) first = ti;
+      last = ti;
+      qi++;
+    }
+  }
+  if (qi < query.length) return null;
+  return last - first;
+}
+
+/// Score [query] against a single [shortcode]. Returns null when there is no
+/// match at any tier. Both sides are normalized first, so separators are
+/// ignored. This is the desktop-identical half of the ranking.
+EmojiMatch? scoreShortcodeMatch(String query, String shortcode) {
+  final q = collapseSeparators(query);
+  if (q.isEmpty) return null;
+  final target = collapseSeparators(shortcode);
+  if (target.isEmpty) return null;
+
+  if (q == target) return const EmojiMatch(tier: _tierExact, score: 0);
+  if (target.startsWith(q)) {
+    return const EmojiMatch(tier: _tierShortcodePrefix, score: 0);
+  }
+  final index = target.indexOf(q);
+  if (index != -1) {
+    return EmojiMatch(tier: _tierShortcodeSubstring, score: index);
+  }
+  final span = _subsequenceSpan(q, target);
+  if (span != null) return EmojiMatch(tier: _tierSubsequence, score: span);
+  return null;
+}
+
+/// Score [query] against an entry's name and keywords, word by word. Used to
+/// top up shortcode matching so a query like `smiling` finds emoji whose
+/// shortcode doesn't contain it.
+EmojiMatch? _scoreKeywordMatch(
+  String query,
+  String name,
+  List<String> keywords,
+) {
+  final q = query.toLowerCase().trim();
+  if (q.isEmpty) return null;
+
+  var bestTier = _noMatch;
+  var bestScore = 0;
+
+  // Earlier words rank better: the name comes before the keywords, and within
+  // each the dataset's own order is meaningful.
+  void consider(String candidate, int wordIndex) {
+    if (bestTier == _tierKeywordPrefix) return;
+    final word = candidate.toLowerCase();
+    if (word.isEmpty) return;
+    final tier = word.startsWith(q)
+        ? _tierKeywordPrefix
+        : word.contains(q)
+        ? _tierKeywordSubstring
+        : _noMatch;
+    if (tier < bestTier) {
+      bestTier = tier;
+      bestScore = wordIndex;
+    }
+  }
+
+  var wordIndex = 0;
+  for (final word in name.split(_wordSplit)) {
+    consider(word, wordIndex++);
+  }
+  for (final keyword in keywords) {
+    for (final word in keyword.split(_wordSplit)) {
+      consider(word, wordIndex++);
+    }
+  }
+
+  if (bestTier == _noMatch) return null;
+  return EmojiMatch(tier: bestTier, score: bestScore);
+}
+
+class _Scored<T> {
+  final T item;
+  final int tier;
+  final int score;
+  final String code;
+
+  const _Scored({
+    required this.item,
+    required this.tier,
+    required this.score,
+    required this.code,
+  });
+}
+
+int _compare<T>(_Scored<T> a, _Scored<T> b) {
+  if (a.tier != b.tier) return a.tier - b.tier;
+  if (a.score != b.score) return a.score - b.score;
+  // Shorter shortcode is the more specific match, then alphabetical for a
+  // stable result.
+  if (a.code.length != b.code.length) return a.code.length - b.code.length;
+  return a.code.compareTo(b.code);
+}
+
+/// Rank [items] by how well their shortcode matches [query], best first, capped
+/// at [limit]. Mirrors desktop's `rankByShortcode` — used for the custom-emoji
+/// palette, which has no names or keywords.
+List<T> rankByShortcode<T>(
+  String query,
+  List<T> items,
+  String Function(T item) shortcodeOf, {
+  int? limit,
+}) {
+  if (limit != null && limit <= 0) return const [];
+  final scored = <_Scored<T>>[];
+  for (final item in items) {
+    final code = shortcodeOf(item);
+    final match = scoreShortcodeMatch(query, code);
+    if (match == null) continue;
+    scored.add(
+      _Scored(item: item, tier: match.tier, score: match.score, code: code),
+    );
+  }
+  scored.sort(_compare);
+  final ranked = scored.map((entry) => entry.item).toList();
+  if (limit == null || ranked.length <= limit) return ranked;
+  return ranked.sublist(0, limit);
+}
+
+/// Rank standard emoji by shortcode, name, and keywords, best first.
+List<EmojiEntry> searchEmoji(
+  String query,
+  List<EmojiEntry> entries, {
+  int? limit,
+}) {
+  if (limit != null && limit <= 0) return const [];
+  final scored = <_Scored<EmojiEntry>>[];
+  for (final entry in entries) {
+    final shortcode = scoreShortcodeMatch(query, entry.id);
+    final keyword = _scoreKeywordMatch(query, entry.name, entry.keywords);
+    final match = switch ((shortcode, keyword)) {
+      (null, null) => null,
+      (final EmojiMatch only, null) => only,
+      (null, final EmojiMatch only) => only,
+      (final EmojiMatch a, final EmojiMatch b) => a.tier <= b.tier ? a : b,
+    };
+    if (match == null) continue;
+    scored.add(
+      _Scored(
+        item: entry,
+        tier: match.tier,
+        score: match.score,
+        code: entry.id,
+      ),
+    );
+  }
+  scored.sort(_compare);
+  final ranked = scored.map((entry) => entry.item).toList();
+  if (limit == null || ranked.length <= limit) return ranked;
+  return ranked.sublist(0, limit);
+}

mobile/lib/shared/emoji/native_emoji_glyph.dart

@@ -0,0 +1,22 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+
+/// A standalone system emoji whose visual centre matches its surrounding UI.
+///
+/// Apple's emoji glyphs sit slightly low inside Flutter's text box. Keep the
+/// layout box unchanged and lift only the painted glyph on iOS; Android's
+/// system emoji metrics are already visually centred.
+class NativeEmojiGlyph extends StatelessWidget {
+  final String emoji;
+  final double size;
+
+  const NativeEmojiGlyph({super.key, required this.emoji, required this.size});
+
+  @override
+  Widget build(BuildContext context) {
+    final glyph = Text(emoji, style: TextStyle(fontSize: size));
+    if (defaultTargetPlatform != TargetPlatform.iOS) return glyph;
+
+    return Transform.translate(offset: const Offset(0, -1), child: glyph);
+  }
+}

mobile/lib/shared/emoji/positive_emoji.dart

@@ -0,0 +1,91 @@
+/// The emoji that earn a particle burst.
+///
+/// Ported verbatim from `POSITIVE_EMOJI_PARTICLES` in
+/// `desktop/src/shared/ui/EmojiBurstProvider.tsx`. Only affirmation reacts
+/// celebrate — a 😢 or 👎 shouldn't throw confetti — so the three groups below
+/// are the whole gate, and both clients must agree on them or the same reaction
+/// bursts on one device and not the other.
+library;
+
+const heartParticleEmojis = <String>[
+  '\u{2764}\u{FE0F}', // ❤️
+  '\u{1FA77}', // 🩷
+  '\u{1F9E1}', // 🧡
+  '\u{1F49B}', // 💛
+  '\u{1F49A}', // 💚
+  '\u{1FA75}', // 🩵
+  '\u{1F499}', // 💙
+  '\u{1F49C}', // 💜
+  '\u{1F90E}', // 🤎
+  '\u{1F5A4}', // 🖤
+  '\u{1FA76}', // 🩶
+  '\u{1F90D}', // 🤍
+  '\u{2764}\u{FE0F}\u{200D}\u{1F525}', // ❤️‍🔥
+  '\u{2764}\u{FE0F}\u{200D}\u{1FA79}', // ❤️‍🩹
+  '\u{1F496}', // 💖
+  '\u{1F495}', // 💕
+  '\u{1F497}', // 💗
+  '\u{1F493}', // 💓
+  '\u{1F49E}', // 💞
+  '\u{1F498}', // 💘
+  '\u{1F49D}', // 💝
+  '\u{2763}\u{FE0F}', // ❣️
+  '\u{2665}\u{FE0F}', // ♥️
+];
+
+const positiveReactionParticleEmojis = <String>[
+  '\u{1F44D}', // 👍
+  '\u{1F44F}', // 👏
+  '\u{1F64C}', // 🙌
+  '\u{1F64F}', // 🙏
+  '\u{1F4AF}', // 💯
+  '\u{1F525}', // 🔥
+  '\u{2728}', // ✨
+  '\u{2B50}', // ⭐
+  '\u{1F31F}', // 🌟
+  '\u{1F389}', // 🎉
+  '\u{1F38A}', // 🎊
+  '\u{1F973}', // 🥳
+  '\u{1F680}', // 🚀
+  '\u{1F4AA}', // 💪
+];
+
+const positiveFaceParticleEmojis = <String>[
+  '\u{1F600}', // 😀
+  '\u{1F603}', // 😃
+  '\u{1F604}', // 😄
+  '\u{1F601}', // 😁
+  '\u{1F60A}', // 😊
+  '\u{1F607}', // 😇
+  '\u{1F642}', // 🙂
+  '\u{1F60D}', // 😍
+  '\u{1F929}', // 🤩
+  '\u{1F970}', // 🥰
+  '\u{1F618}', // 😘
+  '\u{1F60B}', // 😋
+  '\u{1F60E}', // 😎
+  '\u{1F602}', // 😂
+  '\u{1F923}', // 🤣
+];
+
+const positiveEmojiParticles = <String>[
+  ...heartParticleEmojis,
+  ...positiveReactionParticleEmojis,
+  ...positiveFaceParticleEmojis,
+];
+
+/// Emoji presentation selectors carry no meaning for this comparison, and the
+/// same emoji reaches us with and without one depending on where it came from
+/// (the emoji-mart dataset, a hand-typed reaction, an older client). Desktop
+/// gets away with exact set membership because its picker is the only producer;
+/// mobile reactions also arrive off the wire, so fold the selector away.
+String _foldSelectors(String emoji) =>
+    emoji.trim().replaceAll('\u{FE0F}', '').replaceAll('\u{FE0E}', '');
+
+final Set<String> _positiveEmojiParticleSet = {
+  for (final emoji in positiveEmojiParticles) _foldSelectors(emoji),
+};
+
+/// Whether [emoji] should burst. Mirrors desktop's `isPositiveEmojiParticle`.
+bool isPositiveEmojiParticle(String emoji) =>
+    _positiveEmojiParticleSet.contains(_foldSelectors(emoji));