functions for each of the class' virtual functions. Possibly also
some macros for GST_MIXER_CHANNEL_HAS_FLAG () or _get_channel ().
+How to register these? Let's say that we use osssrc as an example.
+
+typedef struct _GstOssMixer {
+ GstMixer mixer;
+
+ GstElement *element;
+
+ [.. more? ..]
+} GstOssMixer;
+
+typedef struct _GstOssMixerClass {
+ GstMixerClass klass;
+} GstOssMixerClass;
+
+[..]
+
+static void
+gst_ossmixer_class_init (GstOssMixerClass *klass)
+{
+ GstMixerClass *mix_klass = (GstMixerClass *) klass;
+
+ [.. set virtual functions to their oss/mixer counterparts here ..]
+}
+
+[..]
+
+static void
+gst_osssrc_init (GstOssSrc *osssrc)
+{
+[..]
+ gst_element_register_interface (GST_ELEMENT (osssrc),
+ "mixer",
+ gst_osssrc_get_interface);
+[..]
+}
+
+static GstInterface *
+gst_osssrc_get_interface (GstElement *element,
+ const gchar *name)
+{
+ GstOssMixer *mixer;
+
+ g_assert (strcmp (name, "mixer") == 0);
+
+ mixer = g_object_new (GST_TYPE_OSS_MIXER, NULL);
+ mixer->element = element;
+[..]
+
+ return (GstInterface *) mixer;
+}
+
+And yes, that's quite a piece of code, but you didn't expect
+that we could make a mixer in five lines of code, did you?
+However, applications now *can*!
+
+There might be some refcounting issues here: get_interface ()
+should ref () the element, and we should set a mixer dispose
+handler to unref () it again. Then, too, we could add a pointer
+to the file descriptor in the osssrc/osssink, too, and we'd
+have full access to the device.
+However, that's implementation. Let's first worry about general
+design.
+
4b) overlay
-----------
Overlay is used in both in- and output, too. Think of v4lsrc,
GstOverlayNorm *norm);
const gchar * (* get_norm) (GstOverlay *overlay);
void (* set_xwindowid) (GstOverlay *overlay,
- XWindowID xid);
+ XID xid);
} GstOverlayClass;
+That's all!
+
4c) user input
--------------
And yes, user input could be an interface too. Even better, it