115 lines
2.7 KiB
Dart
115 lines
2.7 KiB
Dart
import 'dart:async';
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import 'dart:js_interop';
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import 'package:flutter/foundation.dart';
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import 'spelling_tts_backend.dart';
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SpellingTtsBackend createSpellingTtsBackend() => _WebSpeechBackend();
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@JS('speechSynthesis')
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external SpeechSynthesis get _speechSynthesis;
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@JS()
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extension type SpeechSynthesis._(JSObject _) implements JSObject {
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external void speak(SpeechSynthesisUtterance utterance);
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external void cancel();
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}
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@JS()
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extension type SpeechSynthesisUtterance._(JSObject _) implements JSObject {
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external SpeechSynthesisUtterance();
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external String text;
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external String lang;
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external double rate;
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external double pitch;
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@JS('onend')
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external set onEnd(JSFunction? listener);
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@JS('onerror')
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external set onError(JSFunction? listener);
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}
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class _WebSpeechBackend implements SpellingTtsBackend {
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Completer<void>? _pending;
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@override
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Future<void> speak(String text, {String? title}) async {
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final String trimmed = text.trim();
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if (trimmed.isEmpty) {
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return;
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}
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if (title != null && title.isNotEmpty) {
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debugPrint('Spelling TTS utterance title: $title');
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}
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await stop();
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final Completer<void> done = Completer<void>();
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_pending = done;
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final SpeechSynthesisUtterance utterance = SpeechSynthesisUtterance();
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utterance.text = trimmed;
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utterance.lang = 'en-US';
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utterance.rate = 0.85;
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utterance.pitch = 1.0;
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utterance.onEnd = (() {
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if (!done.isCompleted) {
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done.complete();
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}
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}).toJS;
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utterance.onError = ((JSAny event) {
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String details = 'unknown';
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if (event.isA<JSObject>()) {
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try {
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final errEvent = event as JSObject;
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details = (errEvent as SpeechSynthesisErrorEvent).error;
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} catch (_) {}
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}
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debugPrint('Spelling web TTS error: $details ($event)');
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if (!done.isCompleted) {
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done.complete();
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}
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}).toJS;
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try {
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_speechSynthesis.speak(utterance);
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await done.future.timeout(
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const Duration(seconds: 30),
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onTimeout: () {
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debugPrint('Spelling web TTS timed out');
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},
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);
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} catch (e, st) {
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debugPrint('Spelling web TTS failed: $e\n$st');
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if (!done.isCompleted) {
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done.complete();
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}
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} finally {
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if (identical(_pending, done)) {
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_pending = null;
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}
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}
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}
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@override
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Future<void> stop() async {
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final Completer<void>? pending = _pending;
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_pending = null;
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try {
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_speechSynthesis.cancel();
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} catch (e, st) {
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debugPrint('Spelling web TTS stop failed: $e\n$st');
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}
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pending?.complete();
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}
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}
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@JS()
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extension type SpeechSynthesisErrorEvent._(JSObject _) implements JSObject {
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external String get error;
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}
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