Media capture session - protect against recursive call

When setting audio input/output for the second time we can end up as nullptr
for input/output device, because of recursive call to setAudioInput/Output with nullptr
from disconnect callback function of our previous input/output. Also, avoid emitting
changed signal twice.

Pick-to: 6.6 6.5
Task-number: QTBUG-122053
Change-Id: Ie47363591a2dc60868a391ccbc3229bd2ff235de
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
(cherry picked from commit 0053d80e068f9b1edd451d87772cff134e3a9e57)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 37 insertions, 2 deletions

diff --git a/src/multimedia/recording/qmediacapturesession.cpp b/src/multimedia/recording/qmediacapturesession.cpp
index e8c3ed138..0ff804bf4 100644
--- a/src/multimedia/recording/qmediacapturesession.cpp
+++ b/src/multimedia/recording/qmediacapturesession.cpp
@@ -184,7 +184,11 @@ void QMediaCaptureSession::setAudioInput(QAudioInput *input)
     QAudioInput *oldInput = d_ptr->audioInput;
     if (oldInput == input)
         return;
-    d_ptr->audioInput = input;
+
+    // To avoid double emit of audioInputChanged
+    // from recursive setAudioInput(nullptr) call.
+    d_ptr->audioInput = nullptr;
+
     if (d_ptr->captureSession)
         d_ptr->captureSession->setAudioInput(nullptr);
     if (oldInput)
@@ -194,6 +198,7 @@ void QMediaCaptureSession::setAudioInput(QAudioInput *input)
         if (d_ptr->captureSession)
             d_ptr->captureSession->setAudioInput(input->handle());
     }
+    d_ptr->audioInput = input;
     emit audioInputChanged();
 }
 
@@ -502,7 +507,12 @@ void QMediaCaptureSession::setAudioOutput(QAudioOutput *output)
     QAudioOutput *oldOutput = d_ptr->audioOutput;
     if (oldOutput == output)
         return;
-    d_ptr->audioOutput = output;
+
+    // We don't want to end up with signal emitted
+    // twice (from recursive call setAudioInput(nullptr)
+    // from oldOutput->setDisconnectFunction():
+    d_ptr->audioOutput = nullptr;
+
     if (d_ptr->captureSession)
         d_ptr->captureSession->setAudioOutput(nullptr);
     if (oldOutput)
@@ -512,6 +522,7 @@ void QMediaCaptureSession::setAudioOutput(QAudioOutput *output)
         if (d_ptr->captureSession)
             d_ptr->captureSession->setAudioOutput(output->handle());
     }
+    d_ptr->audioOutput = output;
     emit audioOutputChanged();
 }
 /*!
diff --git a/tests/auto/integration/qmediacapturesession/tst_qmediacapturesession.cpp b/tests/auto/integration/qmediacapturesession/tst_qmediacapturesession.cpp
index 671bf63ec..c8d487704 100644
--- a/tests/auto/integration/qmediacapturesession/tst_qmediacapturesession.cpp
+++ b/tests/auto/integration/qmediacapturesession/tst_qmediacapturesession.cpp
@@ -79,6 +79,8 @@ private slots:
     void capture_is_not_available_when_Camera_is_null();
     void can_add_ImageCapture_and_capture_during_recording();
 
+    void can_reset_audio_input_output();
+
 private:
     void recordOk(QMediaCaptureSession &session);
     void recordFail(QMediaCaptureSession &session);
@@ -1014,6 +1016,28 @@ void tst_QMediaCaptureSession::testAudioMute()
     QFile(actualLocation).remove();
 }
 
+void tst_QMediaCaptureSession::can_reset_audio_input_output()
+{
+    QAudioInput in1;
+    QMediaCaptureSession session;
+    session.setAudioInput(&in1);
+    QVERIFY(session.audioInput() != nullptr);
+    QAudioInput in2;
+    QSignalSpy changeSpy1(&session, &QMediaCaptureSession::audioInputChanged);
+    session.setAudioInput(&in2);
+    QVERIFY(session.audioInput() != nullptr);
+    QCOMPARE(changeSpy1.count(), 1);
+
+    QAudioOutput out1;
+    session.setAudioOutput(&out1);
+    QVERIFY(session.audioOutput() != nullptr);
+    QSignalSpy changeSpy2(&session, &QMediaCaptureSession::audioOutputChanged);
+    QAudioOutput out2;
+    session.setAudioOutput(&out2);
+    QVERIFY(session.audioOutput() != nullptr);
+    QCOMPARE(changeSpy2.count(), 1);
+}
+
 QTEST_MAIN(tst_QMediaCaptureSession)
 
 #include "tst_qmediacapturesession.moc"