Bug 255134 – AudioContext stops playing when displaying a dialog (window.alert() or window.confirm())

• Component: Web Audio
• Status: NEW

[Kyu Simm]

Problem:
- AudioContext stops playing when displaying a dialog (`window.alert()` or `window.confirm()`)

Steps to Reproduce:
1. Open any website in macOS or iOS Safari. (For iOS Safari steps, unmute your device.)
2. Run the following script in Safari's console. The script adds a button to play a tone and show a dialog.
  ```
  (() => {
    const button = document.createElement('button');
    button.innerText = 'Play audio';
    button.style = 'position: fixed; top:0; left:0; z-index:9999';
    document.body.appendChild(button);

    let isPlaying = false;
    button.addEventListener('click', async () => {
      if (isPlaying) {
        window.alert('Alert!');
      } else {
        isPlaying = true;
        button.innerText = 'Call window.alert';
        const audioContext = new (window.AudioContext || window.webkitAudioContext)();
        const oscillator = audioContext.createOscillator();
        oscillator.type = 'square';
        oscillator.frequency.setValueAtTime(440, audioContext.currentTime); // value in hertz
        oscillator.connect(audioContext.destination);
        oscillator.start();
      }
    });
  })();
  ```
3. Click the "Play audio" button at the top-left corner of the website. You should hear a tone from Safari.
4. Click the "Call window.alert" button.

Actual Results:
- The tone cannot be heard as the dialog appears.

Expected Results:
- The tone should continue playing after the dialog appears or when the dialog is dismissed.

Test Environments:
- macOS Safari 16.4
- iOS Safari 16.3

Additional Information:
- In macOS Chrome 111, the audio continues to play without any pauses.
- In macOS Firefox 111, the audio stops while the dialog is visible, but resumes playing after the dialog is closed.

[Radar WebKit Bug Importer]

<rdar://problem/107985414>