forked from AuroraMiddleware/gtk
37ac7d593e
Your eyes are bloodshot. Your mouth starts to foam. Your hands are shaking. You know your need your fix. NEED MORE ABSTRACTION! 2000-04-12 Federico Mena Quintero <federico@helixcode.com> This comes from an excellent idea by Tim Janik (timj@gtk.org) to hook to the last unref operation. * gdk-pixbuf/gdk-pixbuf.c (gdk_pixbuf_set_last_unref_handler): New function to set the last unref handler for a pixbuf. (gdk_pixbuf_finalize): New function to actually finalize a pixbuf. It calls the pixbuf's destroy notification function and frees the GdkPixbuf structure itself. (gdk_pixbuf_unref): Use the last unref function of the pixbuf if available. * gdk-pixbuf/gdk-pixbuf-private.h (struct _GdkPixbuf): New fields for the last unref handler and its user data. * gdk-pixbuf/gdk-pixbuf-data.c (gdk_pixbuf_new_from_data): Use g_new0() to allocate the pixbuf. * gdk-pixbuf/gdk-pixbuf-loader.c (gdk_pixbuf_loader_class_init): Fixed the call to gtk_signal_new() for the "frame_done" signal; it was not specifying the `frame' argument. * gdk-pixbuf/gdk-pixbuf-animation.c (gdk_pixbuf_animation_get_width): Fixed docstring. (gdk_pixbuf_animation_get_height): Likewise. (gdk_pixbuf_animation_get_num_frames): Likewise. (gdk_pixbuf_animation_get_frames): Likewise. * doc/gdk-pixbuf-sections.txt: Updated with the new functions and types. * doc/tmpl/gdk-pixbuf.sgml: Added the description for GdkColorspace. * doc/tmpl/scaling.sgml: Added the description for GdkInterpType. * doc/tmpl/refcounting.sgml: Updated with the information about the last unref handler. * doc/tmpl/*.sgml: Markup tweaks. * gdk-pixbuf/Makefile.am (libgnomecanvaspixbuf_la_LDFLAGS): Sigh, update the libtool version number for libgnomecanvaspixbuf as well. (libpixbufloader_*_la_LDFLAGS): The loaders need to be versioned as well, or the old ones won't work with the new stuff. Also, renamed the modules as follows. * gdk-pixbuf/gdk-pixbuf-io.c (gdk_pixbuf_load_module): Now the modules are called "libpixbufloader-<format>.so" instead of "libpixbuf-<format>.so". They needed renaming so that the new loaders won't overwrite the old ones; even with the versioning stuff, the new .so symlink to the .so.1.0.0 would overwrite the old real .so file.
189 lines
5.8 KiB
Plaintext
189 lines
5.8 KiB
Plaintext
<!-- ##### SECTION Title ##### -->
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GdkPixbufLoader
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<!-- ##### SECTION Short_Description ##### -->
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Application-driven progressive image loading.
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<!-- ##### SECTION Long_Description ##### -->
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<para>
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#GdkPixbufLoader 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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gdk_pixbuf_new_from_file() 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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</para>
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<para>
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To use #GdkPixbufLoader to load an image, just create a new one,
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and call gdk_pixbuf_loader_write() to send the data to it. When
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done, gdk_pixbuf_loader_close() 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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@GdkPixbuf 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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gdk_pixbuf_loader_get_pixbuf() once this signal has been emitted
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and get the same pixbuf.
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</para>
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<para>
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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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</para>
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<refsect2>
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<title>Loading an animation</title>
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<para>
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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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as well as an "<link
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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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#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 "<link
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linkend="GdkPixbufLoader-frame-done">frame_done</link>" signal
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has been emitted, you can call gdk_pixbuf_loader_get_animation()
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to get the #GdkPixbufAnimation 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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</para>
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</refsect2>
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<!-- ##### SECTION See_Also ##### -->
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<para>
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gdk_pixbuf_new_from_file()
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</para>
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<!-- ##### MACRO GDK_PIXBUF_LOADER ##### -->
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<para>
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Casts a #GtkObject to a #GdkPixbufLoader.
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</para>
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@obj: A GTK+ object.
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<!-- ##### FUNCTION gdk_pixbuf_loader_new ##### -->
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<para>
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</para>
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_loader_write ##### -->
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<para>
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</para>
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@loader:
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@buf:
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@count:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_loader_get_pixbuf ##### -->
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<para>
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</para>
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@loader:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_loader_get_animation ##### -->
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<para>
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</para>
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@loader:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_loader_close ##### -->
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<para>
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</para>
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@loader:
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<!-- ##### SIGNAL GdkPixbufLoader::area-updated ##### -->
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<para>
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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>
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@loader: Loader which emitted the signal.
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@x: X offset of upper-left corner of the updated area.
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@y: Y offset of upper-left corner of the updated area.
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@width: Width of updated area.
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@height: Height of updated area.
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<!-- ##### SIGNAL GdkPixbufLoader::area-prepared ##### -->
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<para>
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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 gdk_pixbuf_loader_get_pixbuf() to
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fetch the partially-loaded pixbuf.
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</para>
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@loader: Loader which emitted the signal.
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<!-- ##### SIGNAL GdkPixbufLoader::frame-done ##### -->
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<para>
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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>
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@loader: Loader which emitted the signal.
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@frame: Frame which just completed loading.
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<!-- ##### SIGNAL GdkPixbufLoader::animation-done ##### -->
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<para>
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This signal is emitted when an animation is done loading.
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</para>
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@loader: Loader which emitted the signal.
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<!-- ##### SIGNAL GdkPixbufLoader::closed ##### -->
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<para>
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This signal is emitted when gdk_pixbuf_loader_close() 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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drives it.
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</para>
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@loader: Loader which emitted the signal.
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<!--
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Local variables:
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mode: sgml
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sgml-parent-document: ("../gdk-pixbuf.sgml" "book" "refsect2" "")
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End:
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-->
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