GStreamer: refactored widget and window control.

Instead of always using xvimagesink as GStreamer backend for the
widget and window control (works only with X11), we now try to
pick a video sink that fits the current configuration.
It first tries a set of known video sinks that can work with
the Qt platform plugin in use. If none is available, it
dynamically picks a video sink available on the system that can be
used with our backend.

Even if the video sink is now picked in a smarter way, xcb is still
the only supported platform plugin. The reason is that it's the
only Unix plugin which can provide a valid native window handle.
Additional work is needed to support other plugins like wayland
or directfb.

Change-Id: I3843dea363d6a0b85a6cc1f2952783b743e48ac6
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

3 files changed, 12 insertions, 14 deletions

diff --git a/src/plugins/gstreamer/camerabin/camerabinservice.cpp b/src/plugins/gstreamer/camerabin/camerabinservice.cpp
index 25fd44817..a22301e2e 100644
--- a/src/plugins/gstreamer/camerabin/camerabinservice.cpp
+++ b/src/plugins/gstreamer/camerabin/camerabinservice.cpp
@@ -124,8 +124,8 @@ CameraBinService::CameraBinService(GstElementFactory *sourceFactory, QObject *pa
 #else
     m_videoWindow = new QGstreamerVideoWindow(this);
 #endif
-    // If the GStreamer sink element is not available (xvimagesink), don't provide
-    // the video window control since it won't work anyway.
+    // If the GStreamer video sink is not available, don't provide the video window control since
+    // it won't work anyway.
     if (!m_videoWindow->videoSink()) {
         delete m_videoWindow;
         m_videoWindow = 0;
@@ -133,9 +133,8 @@ CameraBinService::CameraBinService(GstElementFactory *sourceFactory, QObject *pa
 #if defined(HAVE_WIDGETS)
     m_videoWidgetControl = new QGstreamerVideoWidgetControl(this);
 
-    // If the GStreamer sink element is not available (xvimagesink or ximagesink), don't provide
-    // the video widget control since it won't work anyway.
-    // QVideoWidget will fall back to QVideoRendererControl in that case.
+    // If the GStreamer video sink is not available, don't provide the video widget control since
+    // it won't work anyway. QVideoWidget will fall back to QVideoRendererControl in that case.
     if (!m_videoWidgetControl->videoSink()) {
         delete m_videoWidgetControl;
         m_videoWidgetControl = 0;
diff --git a/src/plugins/gstreamer/mediacapture/qgstreamercaptureservice.cpp b/src/plugins/gstreamer/mediacapture/qgstreamercaptureservice.cpp
index bf9b474d6..a29c1d26f 100644
--- a/src/plugins/gstreamer/mediacapture/qgstreamercaptureservice.cpp
+++ b/src/plugins/gstreamer/mediacapture/qgstreamercaptureservice.cpp
@@ -102,8 +102,8 @@ QGstreamerCaptureService::QGstreamerCaptureService(const QString &service, QObje
         m_videoRenderer = new QGstreamerVideoRenderer(this);
 
         m_videoWindow = new QGstreamerVideoWindow(this);
-        // If the GStreamer sink element is not available (xvimagesink), don't provide
-        // the video window control since it won't work anyway.
+        // If the GStreamer video sink is not available, don't provide the video window control since
+        // it won't work anyway.
         if (!m_videoWindow->videoSink()) {
             delete m_videoWindow;
             m_videoWindow = 0;
@@ -112,9 +112,8 @@ QGstreamerCaptureService::QGstreamerCaptureService(const QString &service, QObje
 #if defined(HAVE_WIDGETS)
         m_videoWidgetControl = new QGstreamerVideoWidgetControl(this);
 
-        // If the GStreamer sink element is not available (xvimagesink or ximagesink), don't provide
-        // the video widget control since it won't work anyway.
-        // QVideoWidget will fall back to QVideoRendererControl in that case.
+        // If the GStreamer video sink is not available, don't provide the video widget control since
+        // it won't work anyway. QVideoWidget will fall back to QVideoRendererControl in that case.
         if (!m_videoWidgetControl->videoSink()) {
             delete m_videoWidgetControl;
             m_videoWidgetControl = 0;
diff --git a/src/plugins/gstreamer/mediaplayer/qgstreamerplayerservice.cpp b/src/plugins/gstreamer/mediaplayer/qgstreamerplayerservice.cpp
index 48cbd937a..69250c0b3 100644
--- a/src/plugins/gstreamer/mediaplayer/qgstreamerplayerservice.cpp
+++ b/src/plugins/gstreamer/mediaplayer/qgstreamerplayerservice.cpp
@@ -99,8 +99,8 @@ QGstreamerPlayerService::QGstreamerPlayerService(QObject *parent):
 #else
     m_videoWindow = new QGstreamerVideoWindow(this);
 #endif
-    // If the GStreamer sink element is not available (xvimagesink), don't provide
-    // the video window control since it won't work anyway.
+    // If the GStreamer video sink is not available, don't provide the video window control since
+    // it won't work anyway.
     if (!m_videoWindow->videoSink()) {
         delete m_videoWindow;
         m_videoWindow = 0;
@@ -109,8 +109,8 @@ QGstreamerPlayerService::QGstreamerPlayerService(QObject *parent):
 #if defined(HAVE_WIDGETS)
     m_videoWidget = new QGstreamerVideoWidgetControl(this);
 
-    // If the GStreamer sink element is not available (xvimagesink or ximagesink), don't provide
-    // the video widget control since it won't work anyway.
+    // If the GStreamer video sink is not available, don't provide the video widget control since
+    // it won't work anyway.
     // QVideoWidget will fall back to QVideoRendererControl in that case.
     if (!m_videoWidget->videoSink()) {
         delete m_videoWidget;