2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2000 Wim Taymans <wtay@chello.be>
5 * gstpadtemplate.c: Templates for pad creation
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 * Boston, MA 02111-1307, USA.
24 * SECTION:gstpadtemplate
25 * @short_description: Describe the media type of a pad.
26 * @see_also: #GstPad, #GstElementFactory
28 * Padtemplates describe the possible media types a pad or an elementfactory can
29 * handle. This allows for both inspection of handled types before loading the
30 * element plugin as well as identifying pads on elements that are not yet
31 * created (request or sometimes pads).
33 * Pad and PadTemplates have #GstCaps attached to it to describe the media type
34 * they are capable of dealing with. gst_pad_template_get_caps() or
35 * GST_PAD_TEMPLATE_CAPS() are used to get the caps of a padtemplate. It's not
36 * possible to modify the caps of a padtemplate after creation.
38 * PadTemplates have a #GstPadPresence property which identifies the lifetime
39 * of the pad and that can be retrieved with GST_PAD_TEMPLATE_PRESENCE(). Also
40 * the direction of the pad can be retrieved from the #GstPadTemplate with
41 * GST_PAD_TEMPLATE_DIRECTION().
43 * The GST_PAD_TEMPLATE_NAME_TEMPLATE () is important for GST_PAD_REQUEST pads
44 * because it has to be used as the name in the gst_element_request_pad_by_name()
45 * call to instantiate a pad from this template.
47 * Padtemplates can be created with gst_pad_template_new() or with
48 * gst_static_pad_template_get (), which creates a #GstPadTemplate from a
49 * #GstStaticPadTemplate that can be filled with the
50 * convenient GST_STATIC_PAD_TEMPLATE() macro.
52 * A padtemplate can be used to create a pad (see gst_pad_new_from_template()
53 * or gst_pad_new_from_static_template ()) or to add to an element class
54 * (see gst_element_class_add_pad_template ()).
56 * The following code example shows the code to create a pad from a padtemplate.
58 * <title>Create a pad from a padtemplate</title>
60 * GstStaticPadTemplate my_template =
61 * GST_STATIC_PAD_TEMPLATE (
62 * "sink", // the name of the pad
63 * GST_PAD_SINK, // the direction of the pad
64 * GST_PAD_ALWAYS, // when this pad will be present
65 * GST_STATIC_CAPS ( // the capabilities of the padtemplate
67 * "channels = (int) [ 1, 6 ]"
74 * pad = gst_pad_new_from_static_template (&my_template, "sink");
80 * The following example shows you how to add the padtemplate to an
81 * element class, this is usually done in the base_init of the class:
85 * my_element_base_init (gpointer g_class)
87 * GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class);
89 * gst_element_class_add_pad_template (gstelement_class,
90 * gst_static_pad_template_get (&my_template));
95 * Last reviewed on 2006-02-14 (0.10.3)
98 #include "gst_private.h"
101 #include "gstpadtemplate.h"
102 #include "gstenumtypes.h"
103 #include "gstmarshal.h"
104 #include "gstutils.h"
106 #include "gsterror.h"
107 #include "gstvalue.h"
109 #define GST_CAT_DEFAULT GST_CAT_PADS
118 static GstObject *parent_class = NULL;
119 static guint gst_pad_template_signals[LAST_SIGNAL] = { 0 };
121 static void gst_pad_template_class_init (GstPadTemplateClass * klass);
122 static void gst_pad_template_init (GstPadTemplate * templ,
123 GstPadTemplateClass * klass);
124 static void gst_pad_template_dispose (GObject * object);
127 gst_pad_template_get_type (void)
129 static GType padtemplate_type = 0;
131 if (!padtemplate_type) {
132 static const GTypeInfo padtemplate_info = {
133 sizeof (GstPadTemplateClass), NULL, NULL,
134 (GClassInitFunc) gst_pad_template_class_init, NULL, NULL,
135 sizeof (GstPadTemplate),
137 (GInstanceInitFunc) gst_pad_template_init, NULL
141 g_type_register_static (GST_TYPE_OBJECT, "GstPadTemplate",
142 &padtemplate_info, 0);
144 return padtemplate_type;
148 gst_pad_template_class_init (GstPadTemplateClass * klass)
150 GObjectClass *gobject_class;
151 GstObjectClass *gstobject_class;
153 gobject_class = (GObjectClass *) klass;
154 gstobject_class = (GstObjectClass *) klass;
156 parent_class = g_type_class_peek_parent (klass);
159 * GstPadTemplate::pad-created:
160 * @pad_template: the object which received the signal.
161 * @pad: the pad that was created.
163 * This signal is fired when an element creates a pad from this template.
165 gst_pad_template_signals[TEMPL_PAD_CREATED] =
166 g_signal_new ("pad-created", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
167 G_STRUCT_OFFSET (GstPadTemplateClass, pad_created),
168 NULL, NULL, gst_marshal_VOID__OBJECT, G_TYPE_NONE, 1, GST_TYPE_PAD);
170 gobject_class->dispose = gst_pad_template_dispose;
172 gstobject_class->path_string_separator = "*";
176 gst_pad_template_init (GstPadTemplate * templ, GstPadTemplateClass * klass)
178 /* We ensure that the pad template we're creating has a sunken reference.
179 * Inconsistencies in pad templates being floating or sunken has caused
180 * problems in the past with leaks, etc.
182 * For consistency, then, we only produce them with sunken references
183 * owned by the creator of the object
185 if (GST_OBJECT_IS_FLOATING (templ)) {
186 gst_object_ref (templ);
187 gst_object_sink (templ);
192 gst_pad_template_dispose (GObject * object)
194 GstPadTemplate *templ = GST_PAD_TEMPLATE (object);
196 g_free (GST_PAD_TEMPLATE_NAME_TEMPLATE (templ));
197 if (GST_PAD_TEMPLATE_CAPS (templ)) {
198 gst_caps_unref (GST_PAD_TEMPLATE_CAPS (templ));
201 G_OBJECT_CLASS (parent_class)->dispose (object);
204 /* ALWAYS padtemplates cannot have conversion specifications (like src_%d),
205 * since it doesn't make sense.
206 * SOMETIMES padtemplates can do whatever they want, they are provided by the
208 * REQUEST padtemplates can be reverse-parsed (the user asks for 'sink1', the
209 * 'sink%d' template is automatically selected), so we need to restrict their
213 name_is_valid (const gchar * name, GstPadPresence presence)
217 if (presence == GST_PAD_ALWAYS) {
218 if (strchr (name, '%')) {
219 g_warning ("invalid name template %s: conversion specifications are not"
220 " allowed for GST_PAD_ALWAYS padtemplates", name);
223 } else if (presence == GST_PAD_REQUEST) {
224 if ((str = strchr (name, '%')) && strchr (str + 1, '%')) {
225 g_warning ("invalid name template %s: only one conversion specification"
226 " allowed in GST_PAD_REQUEST padtemplate", name);
229 if (str && (*(str + 1) != 's' && *(str + 1) != 'd')) {
230 g_warning ("invalid name template %s: conversion specification must be of"
231 " type '%%d' or '%%s' for GST_PAD_REQUEST padtemplate", name);
234 if (str && (*(str + 2) != '\0')) {
235 g_warning ("invalid name template %s: conversion specification must"
236 " appear at the end of the GST_PAD_REQUEST padtemplate name", name);
245 gst_static_pad_template_get_type (void)
247 static GType staticpadtemplate_type = 0;
249 if (!staticpadtemplate_type) {
250 staticpadtemplate_type =
251 g_pointer_type_register_static ("GstStaticPadTemplate");
253 return staticpadtemplate_type;
257 * gst_static_pad_template_get:
258 * @pad_template: the static pad template
260 * Converts a #GstStaticPadTemplate into a #GstPadTemplate.
262 * Returns: a new #GstPadTemplate.
265 gst_static_pad_template_get (GstStaticPadTemplate * pad_template)
269 if (!name_is_valid (pad_template->name_template, pad_template->presence))
272 new = g_object_new (gst_pad_template_get_type (),
273 "name", pad_template->name_template, NULL);
275 GST_PAD_TEMPLATE_NAME_TEMPLATE (new) = g_strdup (pad_template->name_template);
276 GST_PAD_TEMPLATE_DIRECTION (new) = pad_template->direction;
277 GST_PAD_TEMPLATE_PRESENCE (new) = pad_template->presence;
279 GST_PAD_TEMPLATE_CAPS (new) =
280 gst_caps_make_writable (gst_static_caps_get (&pad_template->static_caps));
286 * gst_pad_template_new:
287 * @name_template: the name template.
288 * @direction: the #GstPadDirection of the template.
289 * @presence: the #GstPadPresence of the pad.
290 * @caps: a #GstCaps set for the template. The caps are taken ownership of.
292 * Creates a new pad template with a name according to the given template
293 * and with the given arguments. This functions takes ownership of the provided
294 * caps, so be sure to not use them afterwards.
296 * Returns: a new #GstPadTemplate.
299 gst_pad_template_new (const gchar * name_template,
300 GstPadDirection direction, GstPadPresence presence, GstCaps * caps)
304 g_return_val_if_fail (name_template != NULL, NULL);
305 g_return_val_if_fail (caps != NULL, NULL);
306 g_return_val_if_fail (direction == GST_PAD_SRC
307 || direction == GST_PAD_SINK, NULL);
308 g_return_val_if_fail (presence == GST_PAD_ALWAYS
309 || presence == GST_PAD_SOMETIMES || presence == GST_PAD_REQUEST, NULL);
311 if (!name_is_valid (name_template, presence)) {
312 gst_caps_unref (caps);
316 new = g_object_new (gst_pad_template_get_type (),
317 "name", name_template, NULL);
319 GST_PAD_TEMPLATE_NAME_TEMPLATE (new) = g_strdup (name_template);
320 GST_PAD_TEMPLATE_DIRECTION (new) = direction;
321 GST_PAD_TEMPLATE_PRESENCE (new) = presence;
322 GST_PAD_TEMPLATE_CAPS (new) = caps;
328 * gst_static_pad_template_get_caps:
329 * @templ: a #GstStaticPadTemplate to get capabilities of.
331 * Gets the capabilities of the static pad template.
333 * Returns: the #GstCaps of the static pad template. If you need to keep a
334 * reference to the caps, take a ref (see gst_caps_ref ()).
337 gst_static_pad_template_get_caps (GstStaticPadTemplate * templ)
339 g_return_val_if_fail (templ, NULL);
341 return (GstCaps *) gst_static_caps_get (&templ->static_caps);
345 * gst_pad_template_get_caps:
346 * @templ: a #GstPadTemplate to get capabilities of.
348 * Gets the capabilities of the pad template.
350 * Returns: the #GstCaps of the pad template. If you need to keep a reference to
351 * the caps, take a ref (see gst_caps_ref ()).
354 gst_pad_template_get_caps (GstPadTemplate * templ)
356 g_return_val_if_fail (GST_IS_PAD_TEMPLATE (templ), NULL);
358 return GST_PAD_TEMPLATE_CAPS (templ);
362 * gst_pad_template_pad_created:
363 * @templ: a #GstPadTemplate that has been created
364 * @pad: the #GstPad that created it
366 * Emit the pad-created signal for this template when created by this pad.
369 gst_pad_template_pad_created (GstPadTemplate * templ, GstPad * pad)
371 g_signal_emit (G_OBJECT (templ),
372 gst_pad_template_signals[TEMPL_PAD_CREATED], 0, pad);