Prettify calling of QMediaDevice signals

The idea is inheriting QPlatformMediaDevices from QObject and
connect it to QMediaDevice instances instead of manual collecting
and managing pointers.

Advantages:
- avoid UB behavior with static object destruction order in case
  a user makes any QMediaDevices static.
- align the signals parent: send singals from the QMediaDevice instance

Task-number: QTBUG-110071
Change-Id: I7c30694210864ff8c6c90c7299abdbf383f398fa
Reviewed-by: Pavel Dubsky <pavel.dubsky@qt.io>
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
(cherry picked from commit a9471cbff3bf9d978620e6e962ea196acdd8dc0b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

11 files changed, 30 insertions, 60 deletions

diff --git a/src/multimedia/android/qandroidmediadevices.cpp b/src/multimedia/android/qandroidmediadevices.cpp
index 9e45479a5..022e758da 100644
--- a/src/multimedia/android/qandroidmediadevices.cpp
+++ b/src/multimedia/android/qandroidmediadevices.cpp
@@ -43,12 +43,12 @@ QPlatformAudioSink *QAndroidMediaDevices::createAudioSink(const QAudioDevice &de
 
 void QAndroidMediaDevices::forwardAudioOutputsChanged()
 {
-    audioOutputsChanged();
+    emit audioOutputsChanged();
 }
 
 void QAndroidMediaDevices::forwardAudioInputsChanged()
 {
-    audioInputsChanged();
+    emit audioInputsChanged();
 }
 
 static void onAudioInputDevicesUpdated(JNIEnv */*env*/, jobject /*thiz*/)
diff --git a/src/multimedia/darwin/qdarwinmediadevices.mm b/src/multimedia/darwin/qdarwinmediadevices.mm
index 1a9dbe218..3ab7e6c05 100644
--- a/src/multimedia/darwin/qdarwinmediadevices.mm
+++ b/src/multimedia/darwin/qdarwinmediadevices.mm
@@ -238,7 +238,7 @@ void QDarwinMediaDevices::onInputsUpdated()
     auto inputs = availableAudioDevices(QAudioDevice::Input);
     if (m_cachedAudioInputs != inputs) {
         m_cachedAudioInputs = inputs;
-        audioInputsChanged();
+        emit audioInputsChanged();
     }
 }
 
@@ -247,7 +247,7 @@ void QDarwinMediaDevices::onOutputsUpdated()
     auto outputs = availableAudioDevices(QAudioDevice::Output);
     if (m_cachedAudioOutputs != outputs) {
         m_cachedAudioOutputs = outputs;
-        audioOutputsChanged();
+        emit audioOutputsChanged();
     }
 }
 
diff --git a/src/multimedia/platform/qplatformmediadevices.cpp b/src/multimedia/platform/qplatformmediadevices.cpp
index 95cf3b7a0..09c26a670 100644
--- a/src/multimedia/platform/qplatformmediadevices.cpp
+++ b/src/multimedia/platform/qplatformmediadevices.cpp
@@ -132,27 +132,8 @@ QPlatformAudioSink *QPlatformMediaDevices::audioOutputDevice(const QAudioFormat
     return p;
 }
 
-void QPlatformMediaDevices::audioInputsChanged() const
-{
-    const auto devices = allMediaDevices();
-    for (auto m : devices)
-        emit m->audioInputsChanged();
-}
-
-void QPlatformMediaDevices::audioOutputsChanged() const
-{
-    const auto devices = allMediaDevices();
-    for (auto m : devices)
-        emit m->audioOutputsChanged();
-}
-
-void QPlatformMediaDevices::videoInputsChanged() const
-{
-    const auto devices = allMediaDevices();
-    for (auto m : devices)
-        emit m->videoInputsChanged();
-}
-
 void QPlatformMediaDevices::prepareAudio() { }
 
 QT_END_NAMESPACE
+
+#include "moc_qplatformmediadevices_p.cpp"
diff --git a/src/multimedia/platform/qplatformmediadevices_p.h b/src/multimedia/platform/qplatformmediadevices_p.h
index 9b8d0d5e7..d475495d1 100644
--- a/src/multimedia/platform/qplatformmediadevices_p.h
+++ b/src/multimedia/platform/qplatformmediadevices_p.h
@@ -17,10 +17,10 @@
 
 #include <private/qtmultimediaglobal_p.h>
 #include <qlist.h>
+#include <qobject.h>
 
 QT_BEGIN_NAMESPACE
 
-class QObject;
 class QMediaDevices;
 class QAudioDevice;
 class QCameraDevice;
@@ -29,11 +29,12 @@ class QPlatformAudioSink;
 class QAudioFormat;
 class QPlatformMediaIntegration;
 
-class Q_MULTIMEDIA_EXPORT QPlatformMediaDevices
+class Q_MULTIMEDIA_EXPORT QPlatformMediaDevices : public QObject
 {
+    Q_OBJECT
 public:
     QPlatformMediaDevices();
-    virtual ~QPlatformMediaDevices();
+    ~QPlatformMediaDevices() override;
 
     static void setDevices(QPlatformMediaDevices *);
     static QPlatformMediaDevices *instance();
@@ -49,26 +50,12 @@ public:
     QPlatformAudioSink *audioOutputDevice(const QAudioFormat &format,
                                           const QAudioDevice &deviceInfo, QObject *parent);
 
-    void addMediaDevices(QMediaDevices *m)
-    {
-        m_devices.append(m);
-    }
-    void removeMediaDevices(QMediaDevices *m)
-    {
-        m_devices.removeAll(m);
-    }
-
-    QList<QMediaDevices *> allMediaDevices() const { return m_devices; }
-
-    void videoInputsChanged() const;
-
     virtual void prepareAudio();
 
-protected:
-    void audioInputsChanged() const;
-    void audioOutputsChanged() const;
-
-    QList<QMediaDevices *> m_devices;
+Q_SIGNALS:
+    void audioInputsChanged();
+    void audioOutputsChanged();
+    void videoInputsChanged();
 };
 
 QT_END_NAMESPACE
diff --git a/src/multimedia/platform/qplatformvideodevices.cpp b/src/multimedia/platform/qplatformvideodevices.cpp
index 9d2fc3c31..e556bb899 100644
--- a/src/multimedia/platform/qplatformvideodevices.cpp
+++ b/src/multimedia/platform/qplatformvideodevices.cpp
@@ -13,7 +13,7 @@ QPlatformVideoDevices::~QPlatformVideoDevices()
 
 void QPlatformVideoDevices::videoInputsChanged()
 {
-    QPlatformMediaDevices::instance()->videoInputsChanged();
+    emit QPlatformMediaDevices::instance()->videoInputsChanged();
 }
 
 QT_END_NAMESPACE
diff --git a/src/multimedia/qmediadevices.cpp b/src/multimedia/qmediadevices.cpp
index d8486e603..7302d3d98 100644
--- a/src/multimedia/qmediadevices.cpp
+++ b/src/multimedia/qmediadevices.cpp
@@ -247,17 +247,19 @@ QCameraDevice QMediaDevices::defaultVideoInput()
 QMediaDevices::QMediaDevices(QObject *parent)
     : QObject(parent)
 {
-    QPlatformMediaDevices::instance()->addMediaDevices(this);
+    auto platformDevices = QPlatformMediaDevices::instance();
+    connect(platformDevices, &QPlatformMediaDevices::videoInputsChanged, this,
+            &QMediaDevices::videoInputsChanged);
+    connect(platformDevices, &QPlatformMediaDevices::audioInputsChanged, this,
+            &QMediaDevices::audioInputsChanged);
+    connect(platformDevices, &QPlatformMediaDevices::audioOutputsChanged, this,
+            &QMediaDevices::audioOutputsChanged);
 }
 
 /*!
     \internal
 */
-QMediaDevices::~QMediaDevices()
-{
-    QPlatformMediaDevices::instance()->removeMediaDevices(this);
-}
-
+QMediaDevices::~QMediaDevices() = default;
 
 QT_END_NAMESPACE
 
diff --git a/src/multimedia/windows/qwindowsmediadevices.cpp b/src/multimedia/windows/qwindowsmediadevices.cpp
index a7e54daf5..1358c317b 100644
--- a/src/multimedia/windows/qwindowsmediadevices.cpp
+++ b/src/multimedia/windows/qwindowsmediadevices.cpp
@@ -125,9 +125,9 @@ public:
     {
         // windowsMediaDevice may be deleted as we are executing the callback
         if (flow == EDataFlow::eCapture) {
-            m_windowsMediaDevices->audioInputsChanged();
+            emit m_windowsMediaDevices->audioInputsChanged();
         } else if (flow == EDataFlow::eRender) {
-            m_windowsMediaDevices->audioOutputsChanged();
+            emit m_windowsMediaDevices->audioOutputsChanged();
         }
     }
 
diff --git a/src/plugins/multimedia/darwin/camera/qavfcamerabase.mm b/src/plugins/multimedia/darwin/camera/qavfcamerabase.mm
index 9a8cd62e8..1cf7bb58c 100644
--- a/src/plugins/multimedia/darwin/camera/qavfcamerabase.mm
+++ b/src/plugins/multimedia/darwin/camera/qavfcamerabase.mm
@@ -218,7 +218,7 @@ void QAVFVideoDevices::updateCameraDevices()
 
     if (cameras != m_cameraDevices) {
         m_cameraDevices = cameras;
-        videoInputsChanged();
+        emit videoInputsChanged();
     }
 }
 
diff --git a/src/plugins/multimedia/ffmpeg/qv4l2camera.cpp b/src/plugins/multimedia/ffmpeg/qv4l2camera.cpp
index fcab72faa..b635a7fce 100644
--- a/src/plugins/multimedia/ffmpeg/qv4l2camera.cpp
+++ b/src/plugins/multimedia/ffmpeg/qv4l2camera.cpp
@@ -54,7 +54,7 @@ QList<QCameraDevice> QV4L2CameraDevices::videoDevices() const
 void QV4L2CameraDevices::checkCameras()
 {
     if (doCheckCameras())
-        videoInputsChanged();
+        emit videoInputsChanged();
 }
 
 static const struct {
diff --git a/src/plugins/multimedia/gstreamer/qgstreamervideodevices.cpp b/src/plugins/multimedia/gstreamer/qgstreamervideodevices.cpp
index 3902d4e9e..510978880 100644
--- a/src/plugins/multimedia/gstreamer/qgstreamervideodevices.cpp
+++ b/src/plugins/multimedia/gstreamer/qgstreamervideodevices.cpp
@@ -122,7 +122,7 @@ void QGstreamerVideoDevices::addDevice(GstDevice *device)
     if (gst_device_has_classes(device, "Video/Source")) {
         gst_object_ref(device);
         m_videoSources.push_back({device, QByteArray::number(m_idGenerator)});
-        videoInputsChanged();
+        emit videoInputsChanged();
         m_idGenerator++;
     }
 }
@@ -134,7 +134,7 @@ void QGstreamerVideoDevices::removeDevice(GstDevice *device)
 
     if (it != m_videoSources.end()) {
         m_videoSources.erase(it);
-        videoInputsChanged();
+        emit videoInputsChanged();
     }
 
     gst_object_unref(device);
diff --git a/src/plugins/multimedia/windows/qwindowsvideodevices.cpp b/src/plugins/multimedia/windows/qwindowsvideodevices.cpp
index 305bb1227..2dae560b9 100644
--- a/src/plugins/multimedia/windows/qwindowsvideodevices.cpp
+++ b/src/plugins/multimedia/windows/qwindowsvideodevices.cpp
@@ -24,7 +24,7 @@ LRESULT QT_WIN_CALLBACK deviceNotificationWndProc(HWND hWnd, UINT message, WPARA
             auto wmd = reinterpret_cast<QWindowsVideoDevices *>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
             if (wmd) {
                 if (wParam == DBT_DEVICEARRIVAL || wParam == DBT_DEVICEREMOVECOMPLETE) {
-                    wmd->videoInputsChanged();
+                    emit wmd->videoInputsChanged();
                 }
             }
         }