Help with Gst.Iterator.find_custom() in python

[Marianna S. Buschle]

Hi, I'm trying to create a function in python to find elements in a bin based
on their type (not name).

I have such a function in C which works and I'm trying to convert it to
python but I'm experiencing some issues.

def compare_gtype(element, type):
    print(element)
    print(type)
    
    return 1

def gst_bin_get_by_gtype(bin, type_name):
    factory = Gst.ElementFactory.find(type_name)
    type = factory.get_element_type()
    print(type_name)
    print(type)
    
    print("[" + bin.get_name() + "]: looking up child element of type " +
type.name)

    children = bin.iterate_recurse()        
    if children:
        print(children)
        print(children.type)
        found, elem = children.find_custom(compare_gtype, type)
    else:
        print("Error")

    if found:
        print("Found")
        return elem
    else:
        print("Not Found")
        return None

This is the output I get:

filesink
<GType GstFileSink (140449056935968)>
[pipeline0]: looking up child element of type GstFileSink
<Gst.Iterator object at 0x7fbcded2bdc0 (GstIterator at 0x7fbcd0009220)>
<GType GstElement (140449054520272)>
<GType GstFileSink (140449056935968)>
140448920294640
<GType GstFileSink (140449056935968)>
140448920294640
<GType GstFileSink (140449056935968)>
140448920294640
<GType GstFileSink (140449056935968)>
140448920294640
<GType GstFileSink (140449056935968)>
140448920294640
API Exception: {'type': 'TypeError', 'args': ('unknown type (null)',),
'message': 'unknown type (null)'}
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/jsonrpc/manager.py", line 113, in
_get_responses
    result = method(*request.args, **request.kwargs)
  File "/home/msb/QtecGit/python-tests/gst_ctrl.py", line 248, in play
    gst_handler.play(index)
  File "/home/msb/QtecGit/python-tests/gst_ctrl.py", line 69, in play
    elem = gst_bin_get_by_gtype(self.pipeline[index], "filesink")
  File "/home/msb/QtecGit/python-tests/gst_ctrl.py", line 42, in
gst_bin_get_by_gtype
    found, elem = children.find_custom(compare_gtype, type)
TypeError: unknown type (null)

So for me it seems like the find_custom() is not passing the GstElement from
the iterator to the compare_gtype() function...

And this is the pipeline it is searching (no filesink):
filesrc name=replay location=/home/msb/test.ts ! decodebin ! videoconvert !
ximagesink sync=1

And just for reference the code in C:

static gint
compare_gtype(const GValue *velement, GType type)
{
	gint eq = 1;
	GstElement *element = g_value_get_object(velement);

	GST_OBJECT_LOCK(element);
	if (G_OBJECT_TYPE(element) == type)
		eq = 0;
	GST_OBJECT_UNLOCK(element);

	return eq;
}

static GstElement *
gst_bin_get_by_gtype(GstBin *bin, GType type)
{
	GstIterator *children;
	GValue result = { 0, };
	GstElement *element;
	gboolean found;

	g_return_val_if_fail(GST_IS_BIN(bin), NULL);

	QTEC_DEBUG("[%s]: looking up child element of type %s",
		   GST_ELEMENT_NAME(bin), g_type_name(type));

	children = gst_bin_iterate_recurse(bin);
	found = gst_iterator_find_custom(children,
					 (GCompareFunc) compare_gtype,
					 &result, (gpointer) type);
	gst_iterator_free(children);

	if (found) {
		element = g_value_dup_object(&result);
		g_value_unset(&result);
	} else {
		element = NULL;
	}

	return element;
}

        GstElementFactory * proxysrc_factory =
gst_element_factory_find("proxysrc");

	if (!proxysrc_factory)
		return FALSE;

	GType proxysrc_type =
gst_element_factory_get_element_type(proxysrc_factory);

	GstElement *psrc = gst_bin_get_by_gtype(GST_BIN(bin), proxysrc_type);



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