gstreamer-sharp: Fix App{Src,Sink} constructors

Apparently GtkSharp expects each object has only one ToggleRef at any
time. Assigning element.Handle into Raw has a consequence that second
ToggleRef attempts to get created but fails on g_object_unref () that
breaks a GObject assertion:

  toggle_refs_notify: assertion failed: (tstack.n_toggle_refs == 1)

This is because toggle references should be removed with
g_object_remove_toggle_ref(), not a simple unref().

In order to avoid duplicate toggle references, introduce
ElementFactory.MakeRaw(), which creates a GstElement without its
accompanying C# object. The returned raw pointer can be assigned into
another GLib.Object without trouble.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1885>

diff --git a/subprojects/gstreamer-sharp/sources/custom/AppSink.cs b/subprojects/gstreamer-sharp/sources/custom/AppSink.cs
index 2f21822..de90fae 100644 (file)
--- a/subprojects/gstreamer-sharp/sources/custom/AppSink.cs
+++ b/subprojects/gstreamer-sharp/sources/custom/AppSink.cs
@@ -27,9 +27,8 @@ namespace Gst.App {
 
        partial class AppSink 
        {
-               public AppSink (String name) {
-                       var element = ElementFactory.Make ("appsink", name);
-                       Raw = element.Handle;
+               public AppSink (String name) : base(IntPtr.Zero) {
+                       Raw = ElementFactory.MakeRaw("appsink", name);
                }
        }
 }

diff --git a/subprojects/gstreamer-sharp/sources/custom/AppSrc.cs b/subprojects/gstreamer-sharp/sources/custom/AppSrc.cs
index 536725d..ce06671 100644 (file)
--- a/subprojects/gstreamer-sharp/sources/custom/AppSrc.cs
+++ b/subprojects/gstreamer-sharp/sources/custom/AppSrc.cs
@@ -27,9 +27,8 @@ namespace Gst.App {
 
        partial class AppSrc 
        {
-               public AppSrc (String name) {
-                       var element = ElementFactory.Make ("appsrc", name);
-                       Raw = element.Handle;
+               public AppSrc (String name) : base(IntPtr.Zero) {
+                       Raw = ElementFactory.MakeRaw ("appsrc", name);
                }
        }
 }

diff --git a/subprojects/gstreamer-sharp/sources/custom/ElementFactory.cs b/subprojects/gstreamer-sharp/sources/custom/ElementFactory.cs
new file mode 100644 (file)
index 0000000..c6e11a0
--- /dev/null
+++ b/subprojects/gstreamer-sharp/sources/custom/ElementFactory.cs
@@ -0,0 +1,41 @@
+//
+// ElementFactory.cs
+//
+// Authors:
+//   Jakub Adam <jakub.adam@collabora.com>
+//
+// Copyright (C) 2020 Collabora Ltd.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+// 02110-1301  USA
+
+namespace Gst
+{
+       using System;
+       using System.Runtime.InteropServices;
+
+       public partial class ElementFactory
+       {
+               public static IntPtr MakeRaw(string factoryname, string name)
+               {
+                       IntPtr native_factoryname = GLib.Marshaller.StringToPtrGStrdup(factoryname);
+                       IntPtr native_name = GLib.Marshaller.StringToPtrGStrdup(name);
+                       IntPtr raw_ret = gst_element_factory_make(native_factoryname, native_name);
+                       GLib.Marshaller.Free(native_factoryname);
+                       GLib.Marshaller.Free(native_name);
+                       return raw_ret;
+               }
+       }
+}

diff --git a/subprojects/gstreamer-sharp/sources/meson.build b/subprojects/gstreamer-sharp/sources/meson.build
index c327ced..0e75ca0 100644 (file)
--- a/subprojects/gstreamer-sharp/sources/meson.build
+++ b/subprojects/gstreamer-sharp/sources/meson.build
@@ -16,6 +16,7 @@ sources = [
     'custom/DeviceProvider.cs',
     'custom/DynamicSignal.cs',
     'custom/Element.cs',
+    'custom/ElementFactory.cs',
     'custom/FFTF32.cs',
     'custom/Iterator.cs',
     'custom/MapInfo.cs',