example.h 2.95 KB
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/* GStreamer
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 * Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */


#ifndef __GST_EXAMPLE_H__
#define __GST_EXAMPLE_H__

#include <gst/gst.h>

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G_BEGIN_DECLS
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/* This is the definition of the element's object structure. */
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typedef struct _GstExample GstExample;
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/* The structure itself is derived from GstElement, as can be seen by the
 * fact that there's a complete instance of the GstElement structure at
 * the beginning of the object.  This allows the element to be cast to
 * an Element or even an Object.
 */
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struct _GstExample {
  GstElement element;

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  /* We need to keep track of our pads, so we do so here. */
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  GstPad *sinkpad,*srcpad;

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  /* We'll use this to decide whether to do anything to the data we get. */
  gboolean active;
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};

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/* The other half of the object is its class.  The class also derives from
 * the same parent, though it must be the class structure this time.
 * Function pointers for polymophic methods and signals are placed in this
 * structure. */
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typedef struct _GstExampleClass GstExampleClass;
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struct _GstExampleClass {
  GstElementClass parent_class;
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  /* signals */
  void (*asdf) (GstElement *element, GstExample *example);
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};

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/* Five standard preprocessing macros are used in the Gtk+ object system.
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 * The first uses the object's _get_type function to return the GType
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 * of the object.
 */
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#define GST_TYPE_EXAMPLE \
  (gst_example_get_type())
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/* The second is a checking cast to the correct type.  If the object passed
 * is not the right type, a warning will be generated on stderr.
 */
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#define GST_EXAMPLE(obj) \
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  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_EXAMPLE,GstExample))
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/* The third is a checking cast of the class instead of the object. */
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#define GST_EXAMPLE_CLASS(klass) \
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  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_EXAMPLE,GstExampleClass))
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/* The last two simply check to see if the passed pointer is an object or
 * class of the correct type. */
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#define GST_IS_EXAMPLE(obj) \
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  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_EXAMPLE))
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#define GST_IS_EXAMPLE_CLASS(obj) \
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  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_EXAMPLE))
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/* This is the only prototype needed, because it is used in the above
 * GST_TYPE_EXAMPLE macro.
 */
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GType gst_example_get_type(void);
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G_END_DECLS
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#endif /* __GST_EXAMPLE_H__ */