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<!-- ##### SECTION Title ##### -->
GdkPixbufLoader
<!-- ##### SECTION Short_Description ##### -->
Application-driven progressive image loading.
<!-- ##### SECTION Long_Description ##### -->
<para>
#GdkPixbufLoader provides a way for applications to drive the
process of loading an image, by letting them send the image data
directly. Applications can use this functionality instead of
gdk_pixbuf_new_from_file() when they need to parse image data in
small chunks. For example, it should be used when reading an image
from a (potentially) slow network connection, or when loading an
extremely large file.
</para>
<para>
To use #GdkPixbufLoader to load an image, just create a new one, and
call gdk_pixbuf_loader_write() to send the data to it. When done,
gdk_pixbuf_loader_close() should be called to end the stream and
finalize everything. The loader will emit two important signals
throughout the process. The first, #"area_prepared", will be called
as soon as the image has enough information to determine the size of
the image to be used. It will pass a @GdkPixbuf in. If you want to
use it, you can simply ref it. In addition, no actual information
will be passed in yet, so the pixbuf can be safely filled with any
temporary graphics (or an initial color) as needed. You can also
call the gdk_pixbuf_loader_get_pixbuf() once this signal has been
emitted and get the same pixbuf.
</para>
<para>
The other signal, #"area_updated" gets called every
time a region is updated. This way you can update a partially
completed image. Note that you do not know anything about the
completeness of an image from the area updated. For example, in an
interlaced image, you need to make several passes before the image
is done loading.
</para>
<refsect2>
<title>Loading an animation</title>
<para>
Loading an animation is a little more complex then loading an
image. In addition to the above signals, there is also a
#"frame_done" signal, as well as an #"animation_done" signal. The
first lets the application know that it is dealing with an
animation, instead of a static image. It also passes a
#GdkPixbufFrame in the signal. As before, if you want to keep the
frame, you need to ref it. Once the first #"frame_done" signal
has been emitted, you can call gdk_pixbuf_loader_get_animation()
to get the #GdkPixbufAnimation struct. Each subsequent frame goes
through a similar lifecycle. For example #"area_prepared" is
re-emitted. Then #"area_updated" is emitted as many times as
necessary. Finally, #"animation_done" is emitted as soon as all
frames are done.
</para>
</refsect2>
<!-- ##### SECTION See_Also ##### -->
<para>
gdk_pixbuf_new_from_file()
</para>
<!-- ##### MACRO GDK_PIXBUF_LOADER ##### -->
<para>
Casts a #GtkObject to a #GdkPixbufLoader.
</para>
@obj: A GTK+ object.
<!-- ##### FUNCTION gdk_pixbuf_loader_new ##### -->
<para>
</para>
@Returns:
<!-- ##### FUNCTION gdk_pixbuf_loader_write ##### -->
<para>
</para>
@loader:
@buf:
@count:
@Returns:
<!-- ##### FUNCTION gdk_pixbuf_loader_get_pixbuf ##### -->
<para>
</para>
@loader:
@Returns:
<!-- ##### FUNCTION gdk_pixbuf_loader_get_animation ##### -->
<para>
</para>
@loader:
@Returns:
<!-- ##### FUNCTION gdk_pixbuf_loader_close ##### -->
<para>
</para>
@loader:
<!-- ##### SIGNAL GdkPixbufLoader::area-updated ##### -->
<para>
This signal is emitted when a significant area of the image being
loaded has been updated. Normally it means that a complete
scanline has been read in, but it could be a different area as
well. Applications can use this signal to know when to repaint
areas of an image that is being loaded.
</para>
@gdkpixbufloader: the object which received the signal.
@arg1:
@arg2:
@arg3:
@arg4:
<!-- # Unused Parameters # -->
@loader: Loader which emitted the signal.
@x: X offset of upper-left corner of the updated area.
@y: Y offset of upper-left corner of the updated area.
@width: Width of updated area.
@height: Height of updated area.
<!-- ##### SIGNAL GdkPixbufLoader::area-prepared ##### -->
<para>
This signal is emitted when the pixbuf loader has been fed the
initial amount of data that is required to figure out the size and
format of the image that it will create. After this signal is
emitted, applications can call gdk_pixbuf_loader_get_pixbuf() to
fetch the partially-loaded pixbuf.
</para>
@gdkpixbufloader: the object which received the signal.
<!-- # Unused Parameters # -->
@loader: Loader which emitted the signal.
<!-- ##### SIGNAL GdkPixbufLoader::frame-done ##### -->
<para>
</para>
@gdkpixbufloader: the object which received the signal.
<!-- ##### SIGNAL GdkPixbufLoader::animation-done ##### -->
<para>
</para>
@gdkpixbufloader: the object which received the signal.
<!-- ##### SIGNAL GdkPixbufLoader::closed ##### -->
<para>
This signal is emitted when gdk_pixbuf_loader_close() is called.
It can be used by different parts of an application to receive
notification when an image loader is closed by the code that
drives it.
</para>
@gdkpixbufloader: the object which received the signal.
<!-- # Unused Parameters # -->
@loader: Loader which emitted the signal.
<!--
Local variables:
mode: sgml
sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
End:
-->
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