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>

2 files changed, 22 insertions, 6 deletions

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();