Commit aad57970 authored by Sebastian Dröge's avatar Sebastian Dröge

element: Inherit element metadata and pad templates from parent classes

This allows to add pad templates and set metadata in class_init instead of
base_init. base_init is a concept that is not supported by almost all
languages and copying the templates/metadata for subclasses is the more
intuitive way of doing things.

Subclasses can override pad templates of parent classes by adding a new
template with the same now.

Also gst_element_class_add_pad_template() now takes ownership of the
pad template, which was assumed by all code before anyway.

Fixes bug #491501.
parent 8bfdd8c8
......@@ -45,6 +45,11 @@ The 0.11 porting guide
gstelementmetadata.h contains the keys for all standard metadata.
Element metadata and pad templates are inherited from parent classes and
should be added in class_init instead of base_init.
gst_element_class_add_pad_template() takes ownership of the template
* GstPad:
gst_pad_get_caps() does not return writable caps anymore and an explicit
gst_caps_make_writable() needs to be performed. This was the functionality
......
......@@ -238,18 +238,29 @@ static void
gst_element_base_class_init (gpointer g_class)
{
GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
/* FIXME 0.11: Instead of clearing the
* pad template list copy the list and increase the refcount of
* the pad templates by one.
*
* This will make it possible to add pad templates and set element
* details in the class_init functions and is the real GObject way
* of doing things.
* See http://bugzilla.gnome.org/show_bug.cgi?id=491501
GList *node, *padtemplates;
/* Copy the element details here so elements can inherit the
* details from their base class and classes only need to set
* the details in class_init instead of base_init */
element_class->metadata =
element_class->metadata ? gst_structure_copy (element_class->metadata) :
gst_structure_empty_new ("metadata");
/* Copy the pad templates so elements inherit them
* from their base class but elements can add pad templates in class_init
* instead of base_init.
*/
/* FIXME: Do we consider GstPadTemplates as immutable? If so we can
* simply ref them instead of copying.
*/
element_class->metadata = gst_structure_empty_new ("metadata");
element_class->padtemplates = NULL;
padtemplates = g_list_copy (element_class->padtemplates);
for (node = padtemplates; node != NULL; node = node->next) {
GstPadTemplate *tmpl = (GstPadTemplate *) node->data;
node->data = gst_pad_template_new (tmpl->name_template,
tmpl->direction, tmpl->presence, gst_caps_copy (tmpl->caps));
}
element_class->padtemplates = padtemplates;
/* set the factory, see gst_element_register() */
element_class->elementfactory =
......@@ -1270,30 +1281,37 @@ gst_element_iterate_sink_pads (GstElement * element)
/**
* gst_element_class_add_pad_template:
* @klass: the #GstElementClass to add the pad template to.
* @templ: (transfer none): a #GstPadTemplate to add to the element class.
* @templ: (transfer full): a #GstPadTemplate to add to the element class.
*
* Adds a padtemplate to an element class. This is mainly used in the _class_init
* functions of classes. If a pad template with the same name as an already
* existing one is added the old one is replaced by the new one.
*
* Adds a padtemplate to an element class. This is mainly used in the _base_init
* functions of classes.
*/
void
gst_element_class_add_pad_template (GstElementClass * klass,
GstPadTemplate * templ)
{
GList *template_list = klass->padtemplates;
g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
g_return_if_fail (GST_IS_PAD_TEMPLATE (templ));
/* FIXME 0.11: allow replacing the pad templates by
* calling this with the same name as an already existing pad
* template. For this we _must_ _not_ ref the added pad template
* a second time and _must_ document that this function takes
* ownership of the pad template. Otherwise we will leak pad templates
* or the caller unref's the pad template and it disappears */
/* avoid registering pad templates with the same name */
g_return_if_fail (gst_element_class_get_pad_template (klass,
templ->name_template) == NULL);
klass->padtemplates = g_list_append (klass->padtemplates,
gst_object_ref (templ));
/* If we already have a pad template with the same name replace the
* old one. */
while (template_list) {
GstPadTemplate *padtempl = (GstPadTemplate *) template_list->data;
/* Found pad with the same name, replace and return */
if (strcmp (templ->name_template, padtempl->name_template) == 0) {
gst_object_unref (padtempl);
template_list->data = templ;
return;
}
template_list = g_list_next (template_list);
}
klass->padtemplates = g_list_append (klass->padtemplates, templ);
klass->numpadtemplates++;
}
......@@ -1330,7 +1348,7 @@ gst_element_class_add_metadata (GstElementClass * klass,
* multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
*
* Sets the detailed information for a #GstElementClass.
* <note>This function is for use in _base_init functions only.</note>
* <note>This function is for use in _class_init functions only.</note>
*/
void
gst_element_class_set_metadata (GstElementClass * klass,
......
......@@ -78,13 +78,13 @@
* </example>
*
* The following example shows you how to add the padtemplate to an
* element class, this is usually done in the base_init of the class:
* element class, this is usually done in the class_init of the class:
* <informalexample>
* <programlisting>
* static void
* my_element_base_init (gpointer g_class)
* my_element_class_init (GstMyElementClass *klass)
* {
* GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);
* GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
*
* gst_element_class_add_pad_template (gstelement_class,
* gst_static_pad_template_get (&amp;my_template));
......
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