Enable error reporting when failed to initialize backend element

This patch adds an option to report error message when a backend
component cannot be instantiated. This error message is then
displayed in the console with qWarning and in some cases reported
to the app user with error signals. We need further improvements
on the error reporting side.

Additionally, this patch cleans up the code in the .cpp API
classes.

Pick-to: 6.4
Change-Id: Id39865cc8f1e9b52804bf5b9d9b15e738508f860
Reviewed-by: Lars Knoll <lars@knoll.priv.no>

4 files changed, 42 insertions, 46 deletions

diff --git a/src/multimedia/audio/qaudiodecoder.cpp b/src/multimedia/audio/qaudiodecoder.cpp
index c35f7b64f..015ecb2de 100644
--- a/src/multimedia/audio/qaudiodecoder.cpp
+++ b/src/multimedia/audio/qaudiodecoder.cpp
@@ -41,7 +41,12 @@ QT_BEGIN_NAMESPACE
 QAudioDecoder::QAudioDecoder(QObject *parent)
     : QObject(parent)
 {
-    decoder = QPlatformMediaIntegration::instance()->createAudioDecoder(this);
+    auto maybeDecoder = QPlatformMediaIntegration::instance()->createAudioDecoder(this);
+    if (maybeDecoder) {
+        decoder = maybeDecoder.value();
+    } else {
+        qWarning() << "Failed to initialize QAudioDecoder" << maybeDecoder.error();
+    }
 }
 
 
@@ -55,7 +60,7 @@ QAudioDecoder::~QAudioDecoder() = default;
 */
 bool QAudioDecoder::isSupported() const
 {
-    return decoder != nullptr;
+    return bool(decoder);
 }
 
 /*!
@@ -73,9 +78,7 @@ bool QAudioDecoder::isDecoding() const
 */
 QAudioDecoder::Error QAudioDecoder::error() const
 {
-    if (!decoder)
-        return NotSupportedError;
-    return decoder->error();
+    return decoder ? decoder->error() : NotSupportedError;
 }
 
 /*!
@@ -103,12 +106,11 @@ QString QAudioDecoder::errorString() const
 */
 void QAudioDecoder::start()
 {
-    if (decoder == nullptr)
+    if (!decoder)
         return;
 
     // Reset error conditions
     decoder->clearError();
-
     decoder->start();
 }
 
@@ -117,10 +119,8 @@ void QAudioDecoder::start()
 */
 void QAudioDecoder::stop()
 {
-    if (!decoder)
-        return;
-
-    decoder->stop();
+    if (decoder)
+        decoder->stop();
 }
 
 /*!
@@ -130,9 +130,7 @@ void QAudioDecoder::stop()
 */
 QUrl QAudioDecoder::source() const
 {
-    if (decoder)
-        return decoder->source();
-    return QString();
+    return decoder ? decoder->source() : QString{};
 }
 
 /*!
@@ -159,9 +157,7 @@ void QAudioDecoder::setSource(const QUrl &fileName)
 */
 QIODevice *QAudioDecoder::sourceDevice() const
 {
-    if (decoder)
-        return decoder->sourceDevice();
-    return nullptr;
+    return decoder ? decoder->sourceDevice() : nullptr;
 }
 
 /*!
@@ -175,9 +171,8 @@ QIODevice *QAudioDecoder::sourceDevice() const
 */
 void QAudioDecoder::setSourceDevice(QIODevice *device)
 {
-    if (!decoder)
-        return;
-    decoder->setSourceDevice(device);
+    if (decoder)
+        decoder->setSourceDevice(device);
 }
 
 /*!
@@ -190,9 +185,7 @@ void QAudioDecoder::setSourceDevice(QIODevice *device)
 */
 QAudioFormat QAudioDecoder::audioFormat() const
 {
-    if (decoder)
-        return decoder->audioFormat();
-    return QAudioFormat();
+    return decoder ? decoder->audioFormat() : QAudioFormat{};
 }
 
 /*!
@@ -219,7 +212,7 @@ void QAudioDecoder::setAudioFormat(const QAudioFormat &format)
     if (isDecoding())
         return;
 
-    if (decoder != nullptr)
+    if (decoder)
         decoder->setAudioFormat(format);
 }
 
@@ -230,9 +223,7 @@ void QAudioDecoder::setAudioFormat(const QAudioFormat &format)
 */
 bool QAudioDecoder::bufferAvailable() const
 {
-    if (decoder)
-        return decoder->bufferAvailable();
-    return false;
+    return decoder && decoder->bufferAvailable();
 }
 
 /*!
@@ -242,9 +233,7 @@ bool QAudioDecoder::bufferAvailable() const
 
 qint64 QAudioDecoder::position() const
 {
-    if (decoder)
-        return decoder->position();
-    return -1;
+    return decoder ? decoder->position() : -1;
 }
 
 /*!
@@ -254,9 +243,7 @@ qint64 QAudioDecoder::position() const
 
 qint64 QAudioDecoder::duration() const
 {
-    if (decoder)
-        return decoder->duration();
-    return -1;
+    return decoder ? decoder->duration() : -1;
 }
 
 /*!
@@ -271,10 +258,7 @@ qint64 QAudioDecoder::duration() const
 
 QAudioBuffer QAudioDecoder::read() const
 {
-    if (decoder)
-        return decoder->read();
-
-    return QAudioBuffer();
+    return decoder ? decoder->read() : QAudioBuffer{};
 }
 
 // Enums
diff --git a/src/multimedia/audio/qaudiodecoder.h b/src/multimedia/audio/qaudiodecoder.h
index 8594736a4..4a7d6f00a 100644
--- a/src/multimedia/audio/qaudiodecoder.h
+++ b/src/multimedia/audio/qaudiodecoder.h
@@ -76,7 +76,7 @@ Q_SIGNALS:
 
 private:
     Q_DISABLE_COPY(QAudioDecoder)
-    QPlatformAudioDecoder *decoder;
+    QPlatformAudioDecoder *decoder = nullptr;
 };
 
 QT_END_NAMESPACE
diff --git a/src/multimedia/audio/qaudioinput.cpp b/src/multimedia/audio/qaudioinput.cpp
index 8d151d404..f8c088e97 100644
--- a/src/multimedia/audio/qaudioinput.cpp
+++ b/src/multimedia/audio/qaudioinput.cpp
@@ -56,11 +56,17 @@ QAudioInput::QAudioInput(QObject *parent)
 {}
 
 QAudioInput::QAudioInput(const QAudioDevice &device, QObject *parent)
-    : QObject(parent),
-    d(QPlatformMediaIntegration::instance()->createAudioInput(this))
+    : QObject(parent)
 {
-    d->device = device.mode() == QAudioDevice::Input ? device : QMediaDevices::defaultAudioInput();
-    d->setAudioDevice(d->device);
+    auto maybeAudioInput = QPlatformMediaIntegration::instance()->createAudioInput(this);
+    if (maybeAudioInput) {
+        d = maybeAudioInput.value();
+        d->device = device.mode() == QAudioDevice::Input ? device : QMediaDevices::defaultAudioInput();
+        d->setAudioDevice(d->device);
+    } else {
+        d = new QPlatformAudioInput(nullptr);
+        qWarning() << "Failed to initialize QAudioInput" << maybeAudioInput.error();
+    }
 }
 
 QAudioInput::~QAudioInput()
diff --git a/src/multimedia/audio/qaudiooutput.cpp b/src/multimedia/audio/qaudiooutput.cpp
index dd7b31a87..60cf0d476 100644
--- a/src/multimedia/audio/qaudiooutput.cpp
+++ b/src/multimedia/audio/qaudiooutput.cpp
@@ -55,11 +55,17 @@ QAudioOutput::QAudioOutput(QObject *parent)
 {}
 
 QAudioOutput::QAudioOutput(const QAudioDevice &device, QObject *parent)
-    : QObject(parent),
-    d(QPlatformMediaIntegration::instance()->createAudioOutput(this))
+    : QObject(parent)
 {
-    d->device = device.mode() == QAudioDevice::Output ? device : QMediaDevices::defaultAudioOutput();
-    d->setAudioDevice(d->device);
+    auto maybeAudioOutput = QPlatformMediaIntegration::instance()->createAudioOutput(this);
+    if (maybeAudioOutput) {
+        d = maybeAudioOutput.value();
+        d->device = device.mode() == QAudioDevice::Output ? device : QMediaDevices::defaultAudioOutput();
+        d->setAudioDevice(d->device);
+    } else {
+        d = new QPlatformAudioOutput(nullptr);
+        qWarning() << "Failed to initialize QAudioOutput" << maybeAudioOutput.error();
+    }
 }
 
 QAudioOutput::~QAudioOutput()