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<refentry id="GdkPixbufLoader">
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<refentrytitle>GdkPixbufLoader</refentrytitle>
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<manvolnum>3</manvolnum>
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<refmiscinfo>GDK-PIXBUF Library</refmiscinfo>
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<refname>GdkPixbufLoader</refname><refpurpose>Application-driven progressive image loading.</refpurpose>
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<refsynopsisdiv><title>Synopsis</title>
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#include <gdk-pixbuf/gdk-pixbuf.h>
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#define <link linkend="GDK-PIXBUF-LOADER-CAPS">GDK_PIXBUF_LOADER</link> (obj)
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<link linkend="GdkPixbufLoader">GdkPixbufLoader</link>* <link linkend="gdk-pixbuf-loader-new">gdk_pixbuf_loader_new</link> (void);
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<link linkend="gboolean">gboolean</link> <link linkend="gdk-pixbuf-loader-write">gdk_pixbuf_loader_write</link> (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader,
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const <link linkend="guchar">guchar</link> *buf,
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<link linkend="size-t">size_t</link> count);
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<link linkend="GdkPixbuf">GdkPixbuf</link>* <link linkend="gdk-pixbuf-loader-get-pixbuf">gdk_pixbuf_loader_get_pixbuf</link> (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);
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<link linkend="GdkPixbufAnimation">GdkPixbufAnimation</link>* <link linkend="gdk-pixbuf-loader-get-animation">gdk_pixbuf_loader_get_animation</link>
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(<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);
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void <link linkend="gdk-pixbuf-loader-close">gdk_pixbuf_loader_close</link> (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);
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<title>Object Hierarchy</title>
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<link linkend="GtkObject">GtkObject</link>
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<title>Signal Prototypes</title>
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"<link linkend="GdkPixbufLoader-area-updated">area-updated</link>"
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void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gint">gint</link> arg1,
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<link linkend="gint">gint</link> arg2,
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<link linkend="gint">gint</link> arg3,
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<link linkend="gint">gint</link> arg4,
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<link linkend="gpointer">gpointer</link> user_data);
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"<link linkend="GdkPixbufLoader-area-prepared">area-prepared</link>"
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void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);
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"<link linkend="GdkPixbufLoader-frame-done">frame-done</link>"
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void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> arg1,
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<link linkend="gpointer">gpointer</link> user_data);
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"<link linkend="GdkPixbufLoader-animation-done">animation-done</link>"
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void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);
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"<link linkend="GdkPixbufLoader-closed">closed</link>" void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);
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<title>Description</title>
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<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> provides a way for applications to drive the
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process of loading an image, by letting them send the image data
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directly to the loader instead of having the loader read the data
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from a file. Applications can use this functionality instead of
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<link linkend="gdk-pixbuf-new-from-file">gdk_pixbuf_new_from_file</link>() when they need to parse image data in
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small chunks. For example, it should be used when reading an
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image from a (potentially) slow network connection, or when
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loading an extremely large file.
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To use <link linkend="GdkPixbufLoader">GdkPixbufLoader</link> to load an image, just create a new one,
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and call <link linkend="gdk-pixbuf-loader-write">gdk_pixbuf_loader_write</link>() to send the data to it. When
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done, <link linkend="gdk-pixbuf-loader-close">gdk_pixbuf_loader_close</link>() should be called to end the stream
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and finalize everything. The loader will emit two important
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signals throughout the process. The first, "<link
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linkend="GdkPixbufLoader-area-prepared">area_prepared</link>",
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will be called as soon as the image has enough information to
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determine the size of the image to be used. It will pass a
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<parameter>GdkPixbuf</parameter> in. If you want to use it, you can simply ref it. In
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addition, no actual information will be passed in yet, so the
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pixbuf can be safely filled with any temporary graphics (or an
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initial color) as needed. You can also call the
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<link linkend="gdk-pixbuf-loader-get-pixbuf">gdk_pixbuf_loader_get_pixbuf</link>() once this signal has been emitted
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and get the same pixbuf.
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The other signal, "<link
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linkend="GdkPixbufLoader-area-updated">area_updated</link>" gets
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called every time a region is updated. This way you can update a
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partially completed image. Note that you do not know anything
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about the completeness of an image from the area updated. For
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example, in an interlaced image, you need to make several passes
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before the image is done loading.
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<title>Loading an animation</title>
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Loading an animation is a little more complex then loading an
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image. In addition to the above signals, there is also a "<link
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linkend="GdkPixbufLoader-frame-done">frame_done</link>" signal,
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linkend="GdkPixbufLoader-animation-done">animation_done</link>"
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signal. The first lets the application know that it is dealing
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with an animation, instead of a static image. It also passes a
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<link linkend="GdkPixbufFrame">GdkPixbufFrame</link> in the signal. As before, if you want to keep
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the frame, you need to ref it. Once the first "<link
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linkend="GdkPixbufLoader-frame-done">frame_done</link>" signal
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has been emitted, you can call <link linkend="gdk-pixbuf-loader-get-animation">gdk_pixbuf_loader_get_animation</link>()
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to get the <link linkend="GdkPixbufAnimation">GdkPixbufAnimation</link> struct. Each subsequent frame
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goes through a similar lifecycle. For example "<link
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linkend="GdkPixbufLoader-area-prepared">area_prepared</link>" is
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re-emitted. Then "<link
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linkend="GdkPixbufLoader-area-updated">area_updated</link>" is
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emitted as many times as necessary. Finally, "<link
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linkend="GdkPixbufLoader-animation-done">animation_done</link>"
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is emitted as soon as all frames are done.
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<title>Details</title>
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<title><anchor id="GDK-PIXBUF-LOADER-CAPS">GDK_PIXBUF_LOADER()</title>
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<programlisting>#define GDK_PIXBUF_LOADER(obj) (GTK_CHECK_CAST ((obj), GDK_TYPE_PIXBUF_LOADER, GdkPixbufLoader))
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Casts a <link linkend="GtkObject">GtkObject</link> to a <link linkend="GdkPixbufLoader">GdkPixbufLoader</link>.
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>obj</parameter> :</entry>
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<entry>A GTK+ object.
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</tbody></tgroup></informaltable></refsect2>
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<title><anchor id="gdk-pixbuf-loader-new">gdk_pixbuf_loader_new ()</title>
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<programlisting><link linkend="GdkPixbufLoader">GdkPixbufLoader</link>* gdk_pixbuf_loader_new (void);</programlisting>
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Creates a new pixbuf loader object.</para>
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry> A newly-created pixbuf loader.
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</tbody></tgroup></informaltable></refsect2>
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<title><anchor id="gdk-pixbuf-loader-write">gdk_pixbuf_loader_write ()</title>
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<programlisting><link linkend="gboolean">gboolean</link> gdk_pixbuf_loader_write (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader,
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const <link linkend="guchar">guchar</link> *buf,
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<link linkend="size-t">size_t</link> count);</programlisting>
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This will cause a pixbuf loader to parse the next <parameter>count</parameter> bytes of an image.
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It will return TRUE if the data was loaded successfully, and FALSE if an
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error occurred. In the latter case, the loader will be closed, and will not
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accept further writes.</para>
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>loader</parameter> :</entry>
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<entry> A pixbuf loader.
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<row><entry align="right"><parameter>buf</parameter> :</entry>
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<entry> Pointer to image data.
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<row><entry align="right"><parameter>count</parameter> :</entry>
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<entry> Length of the <parameter>buf</parameter> buffer in bytes.
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<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry> <link linkend="TRUE-CAPS">TRUE</link> if the write was successful, or <link linkend="FALSE-CAPS">FALSE</link> if the loader
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cannot parse the buffer.
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</tbody></tgroup></informaltable></refsect2>
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<title><anchor id="gdk-pixbuf-loader-get-pixbuf">gdk_pixbuf_loader_get_pixbuf ()</title>
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<programlisting><link linkend="GdkPixbuf">GdkPixbuf</link>* gdk_pixbuf_loader_get_pixbuf (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);</programlisting>
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Queries the GdkPixbuf that a pixbuf loader is currently creating. In general
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it only makes sense to call this function afer the "area_prepared" signal has
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been emitted by the loader; this means that enough data has been read to know
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the size of the image that will be allocated. If the loader has not received
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enough data via <link linkend="gdk-pixbuf-loader-write">gdk_pixbuf_loader_write</link>(), then this function returns <literal>NULL</literal>.
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The returned pixbuf will be the same in all future calls to the loader, so
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simply calling <link linkend="gdk-pixbuf-ref">gdk_pixbuf_ref</link>() should be sufficient to continue using it. Additionally,
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if the loader is an animation, it will return the first frame of the animation.</para>
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>loader</parameter> :</entry>
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<entry> A pixbuf loader.
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<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry> The GdkPixbuf that the loader is creating, or <literal>NULL</literal> if not
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enough data has been read to determine how to create the image buffer.
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</tbody></tgroup></informaltable></refsect2>
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<title><anchor id="gdk-pixbuf-loader-get-animation">gdk_pixbuf_loader_get_animation ()</title>
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<programlisting><link linkend="GdkPixbufAnimation">GdkPixbufAnimation</link>* gdk_pixbuf_loader_get_animation
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(<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);</programlisting>
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Queries the GdkPixbufAnimation that a pixbuf loader is currently creating.
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In general it only makes sense to call this function afer the "area_prepared"
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signal has been emitted by the loader. If the image is not an animation,
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then it will return <literal>NULL</literal>.</para>
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>loader</parameter> :</entry>
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<entry> A pixbuf loader
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<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry> The GdkPixbufAnimation that the loader is loading, or <literal>NULL</literal> if
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not enough data has been read to determine the information.
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</tbody></tgroup></informaltable></refsect2>
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<title><anchor id="gdk-pixbuf-loader-close">gdk_pixbuf_loader_close ()</title>
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<programlisting>void gdk_pixbuf_loader_close (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *loader);</programlisting>
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Informs a pixbuf loader that no further writes with <link linkend="gdk-pixbuf-load-write">gdk_pixbuf_load_write</link>()
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will occur, so that it can free its internal loading structures.</para>
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>loader</parameter> :</entry>
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<entry> A pixbuf loader.
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</tbody></tgroup></informaltable></refsect2>
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<title>Signals</title>
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<refsect2><title><anchor id="GdkPixbufLoader-area-updated">The "area-updated" signal</title>
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<programlisting>void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gint">gint</link> arg1,
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<link linkend="gint">gint</link> arg2,
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<link linkend="gint">gint</link> arg3,
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<link linkend="gint">gint</link> arg4,
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<link linkend="gpointer">gpointer</link> user_data);</programlisting>
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This signal is emitted when a significant area of the image being
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loaded has been updated. Normally it means that a complete
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scanline has been read in, but it could be a different area as
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well. Applications can use this signal to know when to repaint
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areas of an image that is being loaded.
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>gdkpixbufloader</parameter> :</entry>
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<entry>the object which received the signal.
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<row><entry align="right"><parameter>arg1</parameter> :</entry>
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<row><entry align="right"><parameter>arg2</parameter> :</entry>
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<row><entry align="right"><parameter>arg3</parameter> :</entry>
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<row><entry align="right"><parameter>arg4</parameter> :</entry>
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<row><entry align="right"><parameter>user_data</parameter> :</entry>
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<entry>user data set when the signal handler was connected.</entry></row>
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</tbody></tgroup></informaltable></refsect2><refsect2><title><anchor id="GdkPixbufLoader-area-prepared">The "area-prepared" signal</title>
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<programlisting>void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);</programlisting>
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This signal is emitted when the pixbuf loader has been fed the
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initial amount of data that is required to figure out the size and
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format of the image that it will create. After this signal is
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emitted, applications can call <link linkend="gdk-pixbuf-loader-get-pixbuf">gdk_pixbuf_loader_get_pixbuf</link>() to
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fetch the partially-loaded pixbuf.
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>gdkpixbufloader</parameter> :</entry>
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<entry>the object which received the signal.
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<row><entry align="right"><parameter>user_data</parameter> :</entry>
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<entry>user data set when the signal handler was connected.</entry></row>
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</tbody></tgroup></informaltable></refsect2><refsect2><title><anchor id="GdkPixbufLoader-frame-done">The "frame-done" signal</title>
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<programlisting>void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> arg1,
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<link linkend="gpointer">gpointer</link> user_data);</programlisting>
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This signal is emitted when a frame is done loading. It will be
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emitted for each frame in an animation data stream.
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>gdkpixbufloader</parameter> :</entry>
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<entry>the object which received the signal.
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<row><entry align="right"><parameter>arg1</parameter> :</entry>
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<row><entry align="right"><parameter>user_data</parameter> :</entry>
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<entry>user data set when the signal handler was connected.</entry></row>
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</tbody></tgroup></informaltable></refsect2><refsect2><title><anchor id="GdkPixbufLoader-animation-done">The "animation-done" signal</title>
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<programlisting>void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);</programlisting>
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This signal is emitted when an animation is done loading.
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>gdkpixbufloader</parameter> :</entry>
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<entry>the object which received the signal.
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<row><entry align="right"><parameter>user_data</parameter> :</entry>
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<entry>user data set when the signal handler was connected.</entry></row>
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</tbody></tgroup></informaltable></refsect2><refsect2><title><anchor id="GdkPixbufLoader-closed">The "closed" signal</title>
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<programlisting>void user_function (<link linkend="GdkPixbufLoader">GdkPixbufLoader</link> *gdkpixbufloader,
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<link linkend="gpointer">gpointer</link> user_data);</programlisting>
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This signal is emitted when <link linkend="gdk-pixbuf-loader-close">gdk_pixbuf_loader_close</link>() is called.
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It can be used by different parts of an application to receive
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notification when an image loader is closed by the code that
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</para><informaltable pgwide=1 frame="none" role="params">
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<colspec colwidth="2*">
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<colspec colwidth="8*">
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<row><entry align="right"><parameter>gdkpixbufloader</parameter> :</entry>
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<entry>the object which received the signal.
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<row><entry align="right"><parameter>user_data</parameter> :</entry>
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<entry>user data set when the signal handler was connected.</entry></row>
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</tbody></tgroup></informaltable></refsect2>
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<title>See Also</title>
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<link linkend="gdk-pixbuf-new-from-file">gdk_pixbuf_new_from_file</link>()
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removed
doc/sgml/gdk-pixbuf-loader.sgml
