87 lines
2.9 KiB
Dart
87 lines
2.9 KiB
Dart
import 'package:characters/characters.dart';
|
|
|
|
/// Detects chat messages that consist solely of emoji so the UI can render
|
|
/// them enlarged (à la WhatsApp/iMessage).
|
|
///
|
|
/// Returns the font size to use for such a message, or `null` when [text]
|
|
/// contains any non-emoji, non-whitespace character (i.e. render normally).
|
|
|
|
const int _zwj = 0x200D;
|
|
const int _vs15 = 0xFE0E;
|
|
const int _vs16 = 0xFE0F;
|
|
const int _keycap = 0x20E3;
|
|
|
|
/// Codepoints that only ever glue an emoji sequence together and never stand
|
|
/// on their own — they don't disqualify a cluster from counting as emoji.
|
|
bool _isModifier(int r) =>
|
|
r == _zwj ||
|
|
r == _vs15 ||
|
|
r == _vs16 ||
|
|
r == _keycap ||
|
|
(r >= 0x1F3FB && r <= 0x1F3FF) || // skin-tone modifiers
|
|
(r >= 0xE0020 && r <= 0xE007F); // tag characters (flag sequences)
|
|
|
|
/// The digits, `#` and `*` that become emoji only when combined with the
|
|
/// keycap combining mark.
|
|
bool _isKeycapBase(int r) =>
|
|
r == 0x23 || r == 0x2A || (r >= 0x30 && r <= 0x39);
|
|
|
|
bool _isEmojiRune(int r) {
|
|
// Bulk of modern emoji live in the astral pictograph block: emoticons,
|
|
// transport, supplemental symbols, extended-A, regional indicators, …
|
|
if (r >= 0x1F000 && r <= 0x1FAFF) return true;
|
|
// Scattered BMP emoji ranges (misc symbols, dingbats, arrows, stars, …).
|
|
if (r >= 0x2600 && r <= 0x27BF) return true;
|
|
if (r >= 0x2300 && r <= 0x23FF) return true;
|
|
if (r >= 0x2B00 && r <= 0x2BFF) return true;
|
|
if (r >= 0x2190 && r <= 0x21FF) return true;
|
|
if (r >= 0x25A0 && r <= 0x25FF) return true;
|
|
const singles = {
|
|
0x00A9, 0x00AE, 0x203C, 0x2049, 0x2122, 0x2139,
|
|
0x2934, 0x2935, 0x3030, 0x303D, 0x3297, 0x3299, 0x24C2,
|
|
};
|
|
return singles.contains(r);
|
|
}
|
|
|
|
bool _isEmojiCluster(String cluster) {
|
|
final runes = cluster.runes.toList(growable: false);
|
|
final hasKeycap = runes.contains(_keycap);
|
|
var hasEmoji = false;
|
|
for (final r in runes) {
|
|
if (_isModifier(r)) continue;
|
|
if (_isEmojiRune(r)) {
|
|
hasEmoji = true;
|
|
continue;
|
|
}
|
|
if (hasKeycap && _isKeycapBase(r)) {
|
|
hasEmoji = true;
|
|
continue;
|
|
}
|
|
return false; // a plain text character → not an emoji cluster
|
|
}
|
|
return hasEmoji;
|
|
}
|
|
|
|
/// Maximum number of emojis a message may contain to still be enlarged; longer
|
|
/// emoji strings would turn into a wall of giant glyphs and render normally.
|
|
const int _maxEnlargedEmojis = 3;
|
|
|
|
/// Font size for an emoji-only [text] of at most [_maxEnlargedEmojis] emojis.
|
|
/// `null` means the message is not emoji-only (or has too many emojis) and
|
|
/// should render at the normal body size.
|
|
double? standaloneEmojiFontSize(String text) {
|
|
final trimmed = text.trim();
|
|
if (trimmed.isEmpty) return null;
|
|
|
|
var count = 0;
|
|
for (final cluster in trimmed.characters) {
|
|
if (cluster.trim().isEmpty) continue; // whitespace between emojis
|
|
if (!_isEmojiCluster(cluster)) return null;
|
|
count++;
|
|
if (count > _maxEnlargedEmojis) return null;
|
|
}
|
|
|
|
if (count == 0) return null;
|
|
return 34;
|
|
}
|