fix: Cannot fade 3d source before setting listener position

[chrisnorman7]

Description

If you call play3d with a volume of 0.0 and then fade the resulting sound, no audio will be heard until a call is made to set3dListenerPosition.

Steps To Reproduce

1. Enter the following cod.
2. Run the program.
3. Click the "Play sound" button.
4. Hear nothing.
5. Click the "Set listener position" button.
6. Hear sound.

import 'package:flutter/material.dart';
import 'package:flutter_soloud/flutter_soloud.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // TRY THIS: Try running your application with "flutter run". You'll see
        // the application has a purple toolbar. Then, without quitting the app,
        // try changing the seedColor in the colorScheme below to Colors.green
        // and then invoke "hot reload" (save your changes or press the "hot
        // reload" button in a Flutter-supported IDE, or press "r" if you used
        // the command line to start the app).
        //
        // Notice that the counter didn't reset back to zero; the application
        // state is not lost during the reload. To reset the state, use hot
        // restart instead.
        //
        // This works for code too, not just values: Most code changes can be
        // tested with just a hot reload.
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  /// Create an instance.
  const MyHomePage({
    super.key,
  });

  /// Create state for this widget.
  @override
  MyHomePageState createState() => MyHomePageState();
}

/// State for [MyHomePage].
class MyHomePageState extends State<MyHomePage> {
  /// Build a widget.
  @override
  Widget build(BuildContext context) {
    final soLoud = SoLoud.instance;
    return Scaffold(
      appBar: AppBar(
        title: Text('Example'),
      ),
      body: Column(
        children: [
          TextButton(
            onPressed: () async {
              await soLoud.init();
              final source = await soLoud.loadUrl(
                'https://file-examples.com/storage/fe602ed48f677b2319947f8/2017/11/file_example_MP3_700KB.mp3',
              );
              final handle = await soLoud.play3d(
                source,
                0.0,
                0.0,
                0.0,
                looping: true,
                volume: 0.0,
              );
              soLoud.fadeVolume(handle, 1.0, Duration(seconds: 3));
            },
            autofocus: true,
            child: Text('Play sound'),
          ),
          TextButton(
            onPressed: () => soLoud.set3dListenerPosition(0.0, 0.0, 0.0),
            child: Text('Set listener position'),
          )
        ],
      ),
    );
  }
}

Expected Behavior

You should hear the sound slowly fading up.

Additional Context

There may be a better way to fade sounds up, but I don't know about it.

[alnitak]

Hi @chrisnorman7,

this seems a bug in the C++ SoLoud lib. When using 3D sound, the doc says:

By default, if a sound is inaudible, it's paused, and will resume when it becomes audible again.

That setinaudiblebehavior function is already on the main branch, but not yet on pub.dev. This function works when you already have a sound handle, I need to add the counterpart for the AudioSource that should prevent this issue.

A sound becomes inaudible when the volume goes below 0.01 and maybe something wrong happens here when using 0.

To temporarily solve this issue, please play the sound starting with a volume of 0.01.

I will try to look further and I'll update you.

[chrisnorman7]

Hi, Yes, this fixes the problem. Thank you so much. Take care, Chris Norman