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>GdkPixbufLoader</TITLE
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TITLE="The gdk-pixbuf Library"
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HREF="gdk-pixbuf-animation.html"><LINK
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NAME="GDKPIXBUFLOADER">GdkPixbufLoader</H1
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>GdkPixbufLoader -- Application-driven progressive image loading.</DIV
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CLASS="REFSYNOPSISDIV"
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> #include <gdk-pixbuf/gdk-pixbuf.h>
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-CAPS"
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>GDK_PIXBUF_LOADER</A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-NEW"
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>gdk_pixbuf_loader_new</A
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-WRITE"
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>gdk_pixbuf_loader_write</A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-GET-PIXBUF"
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>gdk_pixbuf_loader_get_pixbuf</A
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HREF="gdkpixbufloader.html"
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GdkPixbufAnimation* <A
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-GET-ANIMATION"
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>gdk_pixbuf_loader_get_animation</A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-CLOSE"
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>gdk_pixbuf_loader_close</A
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HREF="gdkpixbufloader.html"
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>Object Hierarchy</H2
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+----GdkPixbufLoader</PRE
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>Signal Prototypes</H2
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-UPDATED"
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void user_function (<A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-PREPARED"
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void user_function (<A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-FRAME-DONE"
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void user_function (<A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-ANIMATION-DONE"
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void user_function (<A
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HREF="gdkpixbufloader.html"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-CLOSED"
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>" void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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HREF="gdkpixbufloader.html"
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> 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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HREF="gdk-pixbuf-file-loading.html#GDK-PIXBUF-NEW-FROM-FILE"
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>gdk_pixbuf_new_from_file</A
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>() 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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HREF="gdkpixbufloader.html"
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> to load an image, just create a new one,
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-WRITE"
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>gdk_pixbuf_loader_write</A
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>() to send the data to it. When
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-CLOSE"
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>gdk_pixbuf_loader_close</A
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>() 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, "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-PREPARED"
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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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> 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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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-GET-PIXBUF"
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>gdk_pixbuf_loader_get_pixbuf</A
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>() once this signal has been emitted
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and get the same pixbuf.
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> The other signal, "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-UPDATED"
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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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>Loading an animation</H3
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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 "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-FRAME-DONE"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-ANIMATION-DONE"
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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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GdkPixbufFrame in the signal. As before, if you want to keep
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the frame, you need to ref it. Once the first "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-FRAME-DONE"
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has been emitted, you can call <A
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-GET-ANIMATION"
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>gdk_pixbuf_loader_get_animation</A
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to get the GdkPixbufAnimation struct. Each subsequent frame
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goes through a similar lifecycle. For example "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-PREPARED"
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-AREA-UPDATED"
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emitted as many times as necessary. Finally, "<A
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HREF="gdkpixbufloader.html#GDKPIXBUFLOADER-ANIMATION-DONE"
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is emitted as soon as all frames are done.
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NAME="GDK-PIXBUF-LOADER-CAPS"
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>GDK_PIXBUF_LOADER()</H3
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CLASS="PROGRAMLISTING"
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>#define GDK_PIXBUF_LOADER(obj) (GTK_CHECK_CAST ((obj), GDK_TYPE_PIXBUF_LOADER, GdkPixbufLoader))</PRE
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> Casts a GtkObject to a <A
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HREF="gdkpixbufloader.html"
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CLASS="INFORMALTABLE"
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NAME="GDK-PIXBUF-LOADER-NEW"
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>gdk_pixbuf_loader_new ()</H3
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CLASS="PROGRAMLISTING"
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HREF="gdkpixbufloader.html"
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>* gdk_pixbuf_loader_new (void);</PRE
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>Creates a new pixbuf loader object.</P
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CLASS="INFORMALTABLE"
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> A newly-created pixbuf loader.</TD
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NAME="GDK-PIXBUF-LOADER-WRITE"
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>gdk_pixbuf_loader_write ()</H3
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CLASS="PROGRAMLISTING"
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>gboolean gdk_pixbuf_loader_write (<A
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HREF="gdkpixbufloader.html"
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>This will cause a pixbuf loader to parse the next <TT
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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.</P
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CLASS="INFORMALTABLE"
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> A pixbuf loader.</TD
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> Pointer to image data.</TD
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> buffer in bytes.</TD
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> TRUE if the write was successful, or FALSE if the loader
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cannot parse the buffer.</TD
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NAME="GDK-PIXBUF-LOADER-GET-PIXBUF"
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>gdk_pixbuf_loader_get_pixbuf ()</H3
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CLASS="PROGRAMLISTING"
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>GdkPixbuf* gdk_pixbuf_loader_get_pixbuf (<A
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HREF="gdkpixbufloader.html"
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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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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-WRITE"
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>gdk_pixbuf_loader_write</A
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>(), then this function returns <TT
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The returned pixbuf will be the same in all future calls to the loader, so
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HREF="gdk-pixbuf-refcounting.html#GDK-PIXBUF-REF"
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>() 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.</P
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CLASS="INFORMALTABLE"
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> A pixbuf loader.</TD
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> The GdkPixbuf that the loader is creating, or <TT
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enough data has been read to determine how to create the image buffer.</TD
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NAME="GDK-PIXBUF-LOADER-GET-ANIMATION"
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>gdk_pixbuf_loader_get_animation ()</H3
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CLASS="PROGRAMLISTING"
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>GdkPixbufAnimation* gdk_pixbuf_loader_get_animation
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HREF="gdkpixbufloader.html"
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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 <TT
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CLASS="INFORMALTABLE"
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> A pixbuf loader</TD
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> The GdkPixbufAnimation that the loader is loading, or <TT
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not enough data has been read to determine the information.</TD
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NAME="GDK-PIXBUF-LOADER-CLOSE"
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>gdk_pixbuf_loader_close ()</H3
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CLASS="PROGRAMLISTING"
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>void gdk_pixbuf_loader_close (<A
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HREF="gdkpixbufloader.html"
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>Informs a pixbuf loader that no further writes with gdk_pixbuf_load_write()
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will occur, so that it can free its internal loading structures.</P
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CLASS="INFORMALTABLE"
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> A pixbuf loader.</TD
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NAME="GDKPIXBUFLOADER-AREA-UPDATED"
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>The "area-updated" signal</H3
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CLASS="PROGRAMLISTING"
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>void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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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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CLASS="INFORMALTABLE"
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>the object which received the signal.</TD
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>user data set when the signal handler was connected.</TD
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NAME="GDKPIXBUFLOADER-AREA-PREPARED"
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>The "area-prepared" signal</H3
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CLASS="PROGRAMLISTING"
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>void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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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 <A
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-GET-PIXBUF"
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>gdk_pixbuf_loader_get_pixbuf</A
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fetch the partially-loaded pixbuf.
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CLASS="INFORMALTABLE"
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>the object which received the signal.</TD
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>user data set when the signal handler was connected.</TD
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NAME="GDKPIXBUFLOADER-FRAME-DONE"
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>The "frame-done" signal</H3
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CLASS="PROGRAMLISTING"
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>void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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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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CLASS="INFORMALTABLE"
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>the object which received the signal.</TD
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>user data set when the signal handler was connected.</TD
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NAME="GDKPIXBUFLOADER-ANIMATION-DONE"
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>The "animation-done" signal</H3
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CLASS="PROGRAMLISTING"
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>void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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> This signal is emitted when an animation is done loading.
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CLASS="INFORMALTABLE"
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>the object which received the signal.</TD
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>user data set when the signal handler was connected.</TD
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NAME="GDKPIXBUFLOADER-CLOSED"
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>The "closed" signal</H3
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CLASS="PROGRAMLISTING"
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>void user_function (<A
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HREF="gdkpixbufloader.html"
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gpointer user_data);</PRE
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> This signal is emitted when <A
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HREF="gdkpixbufloader.html#GDK-PIXBUF-LOADER-CLOSE"
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>gdk_pixbuf_loader_close</A
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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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CLASS="INFORMALTABLE"
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>the object which received the signal.</TD
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>user data set when the signal handler was connected.</TD
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HREF="gdk-pixbuf-file-loading.html#GDK-PIXBUF-NEW-FROM-FILE"
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>gdk_pixbuf_new_from_file</A
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