Validate that gstreamer elements necessary for operation are available

This patch validates that all elements that are necessary to run
the requested functionality are available. Instead of running
constructors directly, the patch uses a static create() function for
each class. This function first tries to instantiate all necessary
GStreamer plugins and then pass them to the class constructor.
If some element is missing the function returns an error message
describing the element.

Pick-to: 6.4
Fixes: QTBUG-106257
Change-Id: I2b9db3f509e9ad5b760fcc251e634a01c687b790
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Lars Knoll <lars@knoll.priv.no>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
index bd2c815ad..bab24d8c6 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
@@ -1,7 +1,6 @@
 // Copyright (C) 2016 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 QGSTREAMERCAMERACONTROL_H
 #define QGSTREAMERCAMERACONTROL_H
 
@@ -18,6 +17,7 @@
 
 #include <QHash>
 #include <private/qplatformcamera_p.h>
+#include <private/qmultimediautils_p.h>
 #include "qgstreamermediacapture_p.h"
 #include <qgst_p.h>
 
@@ -27,7 +27,8 @@ class QGstreamerCamera : public QPlatformCamera
 {
     Q_OBJECT
 public:
-    QGstreamerCamera(QCamera *camera);
+    static QMaybe<QPlatformCamera *> create(QCamera *camera);
+
     virtual ~QGstreamerCamera();
 
     bool isActive() const override;
@@ -64,6 +65,9 @@ public:
     bool isV4L2Camera() const { return !m_v4l2Device.isEmpty(); }
 
 private:
+    QGstreamerCamera(QGstElement videotestsrc, QGstElement capsFilter, QGstElement videoconvert,
+                     QGstElement videoscale, QCamera *camera);
+
     void updateCameraProperties();
 #if QT_CONFIG(linux_v4l)
     void initV4L2Controls();