From 307c6e1733268eccf8e27e955b6ae06db819549a Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Mon, 19 Oct 2020 08:45:04 +0000
Subject: [PATCH] Bug 1346880 - Test that a muted tab that plays audio via the
 Web Audio API is really muted using PulseAudio monitoring devices.
 r=pehrsons,alwu

Differential Revision: https://phabricator.services.mozilla.com/D93653
---
 dom/media/webaudio/test/mochitest.ini         |  3 +
 .../webaudio/test/test_webAudio_muteTab.html  | 92 +++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 dom/media/webaudio/test/test_webAudio_muteTab.html
diff --git a/dom/media/webaudio/test/mochitest.ini b/dom/media/webaudio/test/mochitest.ini
index ccddac53fb76..3ae4b15fb4e4 100644
--- a/dom/media/webaudio/test/mochitest.ini
+++ b/dom/media/webaudio/test/mochitest.ini
@@ -253,4 +253,7 @@ skip-if = (os == "win" && processor == "aarch64") # aarch64 due to 1538360
 [test_waveShaperInvalidLengthCurve.html]
 [test_WebAudioMemoryReporting.html]
 [test_audioContextParams_sampleRate.html]
+[test_webAudio_muteTab.html]
+scheme = https
+skip-if = os == 'mac' || os == 'win' || toolkit == 'android' # Bug 1404995, no loopback devices on some platforms
 [test_audioContextParams_recordNonDefaultSampleRate.html]
diff --git a/dom/media/webaudio/test/test_webAudio_muteTab.html b/dom/media/webaudio/test/test_webAudio_muteTab.html
new file mode 100644
index 000000000000..9935237d64c4
--- /dev/null
+++ b/dom/media/webaudio/test/test_webAudio_muteTab.html
@@ -0,0 +1,92 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <script type="application/javascript" src="mediaStreamPlayback.js"></script>
+</head>
+<body>
+<pre id="test">
+
+<script>
+(async function() {
+
+  await createHTML({
+    title: "Check tab muting when the tab plays audio via the Web Audio API",
+    bug: "1346880",
+    visible: false
+  });
+  /**
+   * Check that muting a tab results in no audible audio: mute a tab, in which
+   * an OscillatorNode is playing. The default audio output device is a
+   * pulseaudio null-sink. Simulateously, record the other side of the null
+   * sink, and check that no audio has been written to the sink, because the tab
+   * was muted. Then, umute the tab and check that audio is being sent to the
+   * null-sink. */
+  await runTestWhenReady(async () => {
+    let audioDevice = SpecialPowers.getCharPref("media.audio_loopback_dev", "");
+    if (!audioDevice) {
+      todo(false, "No loopback device set by framework. Try --use-test-media-devices");
+      return;
+    }
+
+    // Mute the tab
+    await SpecialPowers.toggleMuteState(true, window.top);
+    // Don't use a loopback tone, the loopback device is here to check that
+    // nothing is output because the tab is muted.
+    DISABLE_LOOPBACK_TONE = true;
+
+    let stream = await getUserMedia({audio: true});
+
+    let ac = new AudioContext();
+
+    let osc = new OscillatorNode(ac);
+    osc.connect(ac.destination);
+    osc.start();
+
+    let analyser = new AudioStreamAnalyser(ac, stream);
+    // Wait for some time, checking there is only ever silent audio in the
+    // loopback stream. `waitForAnalysisSuccess` runs off requestAnimationFrame
+    let silenceFor = 3 / (1 / 60);
+    await analyser.waitForAnalysisSuccess(array => {
+        // `array` has values between 0 and 255, 0 being silence.
+        let sum = array.reduce((acc, v) => { return acc + v; });
+        if (sum == 0) {
+          silenceFor--;
+        } else {
+          info(`Sum of the array values ${sum}`);
+          ok(false, `Found non-silent data in the loopback stream while the tab was muted.`);
+          return true;
+        }
+        if (silenceFor == 0) {
+          ok(true, "Muting the tab was effective");
+        }
+        return silenceFor == 0;
+    });
+
+    // Unmute the tab
+    await SpecialPowers.toggleMuteState(false, window.top);
+
+    await analyser.waitForAnalysisSuccess(array => {
+        // `array` has values between 0 and 255, 0 being silence.
+        let sum = array.reduce((acc, v) => { return acc + v; });
+        if (sum != 0) {
+          info(`Sum after unmuting ${sum}`);
+          ok(true, "Unmuting the tab was effective");
+          return true;
+        } else {
+          // Increment again if we find silence.
+          silenceFor++;
+          if (silenceFor > 100) {
+            ok(false, "Unmuting wasn't effective")
+            return true;
+          }
+          return false;
+        }
+    });
+
+  });
+  finish()
+ })();
+</script>
+</pre>
+</body>
+</html>
