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90 lines
2.5 KiB
Text
90 lines
2.5 KiB
Text
<chapter id="cha-utility">
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<title>Utility functions</title>
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<para>
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while you can use the regular g_object_getv () function to
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query the value of an object property, <application>GStreamer</application>
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provides some easy wrappers for this common operation.
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</para>
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<para>
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Instead of writing the following Gtk+ code to query the GTK_STRING value
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of an object:
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</para>
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<programlisting>
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GtkArg arg;
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guchar *value;
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arg.name = argname;
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g_object_getv (G_OBJECT (object), 1, &arg);
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value = GTK_VALUE_STRING (arg);
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</programlisting>
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<para>
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You can also use:
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</para>
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<programlisting>
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value = gst_util_get_string_arg (object, argname);
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</programlisting>
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<para>
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These convenience functions exist for the following types:
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<itemizedlist>
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<listitem>
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<para>
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gint: with gst_util_get_int_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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gboolean: with gst_util_get_bool_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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glong: with gst_util_get_long_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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gfloat: with gst_util_get_float_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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gdouble: with gst_util_get_double_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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guchar*: with gst_util_get_string_arg ();
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</para>
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</listitem>
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<listitem>
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<para>
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gpointer: with gst_util_get_pointer_arg ();
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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One usually sets object properties using g_object_set (). The problem with this
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method is that you need to know the type of the property. A convenience function,
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gst_utils_set_object_arg () is therefore provided so that you can always set
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the property with a string value. for example:
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</para>
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<programlisting>
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gst_util_set_object_arg (someobject, "int_property", "1000");
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</programlisting>
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<para>
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Will do The Right Thing(tm), converting the string to the type of the property when
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needed.
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</para>
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<para>
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There is also another utility function that can be used to dump a block
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of memory on the console. This function is very usefull for plugin
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developers. The function will dump size bytes of the memory pointed
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to by mem.
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</para>
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<programlisting>
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void gst_util_dump_mem (guchar *mem, guint size);
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</programlisting>
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</chapter>
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