GStreamer: add private API to access pipeline for capture session

Allows users to mess with the underlying gstreamer pipeline of the
`QMediaCaptureSession` like they can with the `QMediaPlayer`

[ChangeLog] QMediaCaptureSession: GStreamer - private interface to
access underlying GstPipeline of QMediaCaptureSession

Pick-to: 6.5 6.6 6.7
Task-number: QTBUG-123830
Change-Id: I5b17240c9951ee8e05dd6cb4a78b203a56794922
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>

8 files changed, 88 insertions, 37 deletions

diff --git a/src/multimedia/CMakeLists.txt b/src/multimedia/CMakeLists.txt
index 183ef7343..8c58545b5 100644
--- a/src/multimedia/CMakeLists.txt
+++ b/src/multimedia/CMakeLists.txt
@@ -67,7 +67,7 @@ qt_internal_add_module(Multimedia
         qmaybe_p.h
         qtmultimediaglobal.h qtmultimediaglobal_p.h
         qerrorinfo_p.h
-        recording/qmediacapturesession.cpp recording/qmediacapturesession.h
+        recording/qmediacapturesession.cpp recording/qmediacapturesession.h recording/qmediacapturesession_p.h
         recording/qmediarecorder.cpp recording/qmediarecorder.h recording/qmediarecorder_p.h
         recording/qscreencapture.cpp recording/qscreencapture.h
         recording/qwindowcapture.cpp recording/qwindowcapture.h
diff --git a/src/multimedia/platform/qplatformmediacapture.cpp b/src/multimedia/platform/qplatformmediacapture.cpp
index 826228764..c8aded824 100644
--- a/src/multimedia/platform/qplatformmediacapture.cpp
+++ b/src/multimedia/platform/qplatformmediacapture.cpp
@@ -1,12 +1,14 @@
 // Copyright (C) 2021 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
-#include <qtmultimediaglobal_p.h>
-#include "qplatformmediacapture_p.h"
-#include "qaudiodevice.h"
-#include "qaudioinput.h"
-#include "qplatformcamera_p.h"
-#include "qplatformsurfacecapture_p.h"
+#include <QtMultimedia/qaudiodevice.h>
+#include <QtMultimedia/qaudioinput.h>
+#include <QtMultimedia/qmediacapturesession.h>
+#include <QtMultimedia/private/qplatformcamera_p.h>
+#include <QtMultimedia/private/qplatformmediacapture_p.h>
+#include <QtMultimedia/private/qmediacapturesession_p.h>
+#include <QtMultimedia/private/qplatformsurfacecapture_p.h>
+#include <QtMultimedia/private/qtmultimediaglobal_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -28,6 +30,15 @@ std::vector<QPlatformVideoSource *> QPlatformMediaCaptureSession::activeVideoSou
     return result;
 }
 
+void *QPlatformMediaCaptureSession::nativePipeline(QMediaCaptureSession *session)
+{
+    auto sessionPrivate = session->d_func();
+    if (!sessionPrivate || !sessionPrivate->captureSession)
+        return nullptr;
+
+    return sessionPrivate->captureSession->nativePipeline();
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qplatformmediacapture_p.cpp"
diff --git a/src/multimedia/platform/qplatformmediacapture_p.h b/src/multimedia/platform/qplatformmediacapture_p.h
index 814fa160c..981cf199b 100644
--- a/src/multimedia/platform/qplatformmediacapture_p.h
+++ b/src/multimedia/platform/qplatformmediacapture_p.h
@@ -64,6 +64,11 @@ public:
     // TBD: implement ordering of the sources basing on the order of adding
     std::vector<QPlatformVideoSource *> activeVideoSources();
 
+    virtual void *nativePipeline() { return nullptr; }
+
+    // private API, the purpose is getting GstPipeline
+    static void *nativePipeline(QMediaCaptureSession *);
+
 Q_SIGNALS:
     void cameraChanged();
     void screenCaptureChanged();
diff --git a/src/multimedia/recording/qmediacapturesession.cpp b/src/multimedia/recording/qmediacapturesession.cpp
index 0ff804bf4..f175cd98e 100644
--- a/src/multimedia/recording/qmediacapturesession.cpp
+++ b/src/multimedia/recording/qmediacapturesession.cpp
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qmediacapturesession.h"
+#include "qmediacapturesession_p.h"
 #include "qaudiodevice.h"
 #include "qcamera.h"
 #include "qmediarecorder.h"
@@ -10,8 +11,6 @@
 #include "qscreencapture.h"
 #include "qwindowcapture.h"
 
-#include <qpointer.h>
-
 #include "qplatformmediaintegration_p.h"
 #include "qplatformmediacapture_p.h"
 #include "qaudioinput.h"
@@ -19,35 +18,19 @@
 
 QT_BEGIN_NAMESPACE
 
-class QMediaCaptureSessionPrivate
+void QMediaCaptureSessionPrivate::setVideoSink(QVideoSink *sink)
 {
-public:
-    QMediaCaptureSession *q = nullptr;
-    QPlatformMediaCaptureSession *captureSession = nullptr;
-    QAudioInput *audioInput = nullptr;
-    QAudioOutput *audioOutput = nullptr;
-    QPointer<QCamera> camera;
-    QPointer<QScreenCapture> screenCapture;
-    QPointer<QWindowCapture> windowCapture;
-    QPointer<QImageCapture> imageCapture;
-    QPointer<QMediaRecorder> recorder;
-    QPointer<QVideoSink> videoSink;
-    QPointer<QObject> videoOutput;
-
-    void setVideoSink(QVideoSink *sink)
-    {
-        if (sink == videoSink)
-            return;
-        if (videoSink)
-            videoSink->setSource(nullptr);
-        videoSink = sink;
-        if (sink)
-            sink->setSource(q);
-        if (captureSession)
-            captureSession->setVideoPreview(sink);
-        emit q->videoOutputChanged();
-    }
-};
+    if (sink == videoSink)
+        return;
+    if (videoSink)
+        videoSink->setSource(nullptr);
+    videoSink = sink;
+    if (sink)
+        sink->setSource(q);
+    if (captureSession)
+        captureSession->setVideoPreview(sink);
+    emit q->videoOutputChanged();
+}
 
 /*!
     \class QMediaCaptureSession
diff --git a/src/multimedia/recording/qmediacapturesession.h b/src/multimedia/recording/qmediacapturesession.h
index c613c3615..1333af7eb 100644
--- a/src/multimedia/recording/qmediacapturesession.h
+++ b/src/multimedia/recording/qmediacapturesession.h
@@ -78,6 +78,8 @@ Q_SIGNALS:
     void audioOutputChanged();
 
 private:
+    friend class QPlatformMediaCaptureSession;
+
     QMediaCaptureSessionPrivate *d_ptr;
     Q_DISABLE_COPY(QMediaCaptureSession)
     Q_DECLARE_PRIVATE(QMediaCaptureSession)
diff --git a/src/multimedia/recording/qmediacapturesession_p.h b/src/multimedia/recording/qmediacapturesession_p.h
new file mode 100644
index 000000000..8702c8d2b
--- /dev/null
+++ b/src/multimedia/recording/qmediacapturesession_p.h
@@ -0,0 +1,44 @@
+// Copyright (C) 2024 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QMEDIACAPTURESESSION_P_H
+#define QMEDIACAPTURESESSION_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtMultimedia/qmediacapturesession.h>
+
+#include <QtCore/qpointer.h>
+
+QT_BEGIN_NAMESPACE
+
+class QMediaCaptureSessionPrivate
+{
+public:
+    QMediaCaptureSession *q = nullptr;
+    QPlatformMediaCaptureSession *captureSession = nullptr;
+    QAudioInput *audioInput = nullptr;
+    QAudioOutput *audioOutput = nullptr;
+    QPointer<QCamera> camera;
+    QPointer<QScreenCapture> screenCapture;
+    QPointer<QWindowCapture> windowCapture;
+    QPointer<QImageCapture> imageCapture;
+    QPointer<QMediaRecorder> recorder;
+    QPointer<QVideoSink> videoSink;
+    QPointer<QObject> videoOutput;
+
+    void setVideoSink(QVideoSink *sink);
+};
+
+QT_END_NAMESPACE
+
+#endif // QMEDIACAPTURESESSION_P_H
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
index 0574a1f1a..720ff5603 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
@@ -322,6 +322,10 @@ QGstreamerVideoSink *QGstreamerMediaCapture::gstreamerVideoSink() const
     return gstVideoOutput ? gstVideoOutput->gstreamerVideoSink() : nullptr;
 }
 
+void *QGstreamerMediaCapture::nativePipeline()
+{
+    return gstPipeline.pipeline();
+}
 
 QT_END_NAMESPACE
 
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
index 6e93e8564..219773413 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
@@ -63,6 +63,8 @@ public:
 
     QGstreamerVideoSink *gstreamerVideoSink() const;
 
+    void *nativePipeline() override;
+
 private:
     void setCameraActive(bool activate);