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67586ddfa4
2007-12-19 Alexander Larsson <alexl@redhat.com>
* gio/migrating.xml:
* gio/overview.xml:
Some minor fixes and additions.
svn path=/trunk/; revision=6154
128 lines
4.7 KiB
XML
128 lines
4.7 KiB
XML
<part>
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<title>GIO Overview</title>
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<chapter>
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<title>Introduction</title>
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<para>
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GIO is striving to provide a modern, easy-to-use VFS API that sits
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at the right level in the library stack. The goal is to overcome the
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shortcomings of GnomeVFS and provide an API that is so good that
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developers prefer it over raw POSIX calls. Among other things
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that means using GObject. It also means not cloning the POSIX
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API, but providing higher-level, document-centric interfaces.
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</para>
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<para>
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The abstract file system model of GIO consists of a number of
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interfaces and base classes for I/O and files:
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<variablelist>
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<varlistentry>
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<term>GFile</term>
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<listitem><para>reference to a file</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GFileInfo</term>
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<listitem><para>information about a file or filesystem</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GFileEnumerator</term>
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<listitem><para>list files in directories</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GDrive</term>
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<listitem><para>represents a drive</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GVolume</term>
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<listitem><para>represents a file system in an abstract way</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GMount</term>
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<listitem><para>represents a mounted file system</para></listitem>
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</varlistentry>
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</variablelist>
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Then there is a number of stream classes, similar to the input and
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output stream hierarchies that can be found in frameworks like Java:
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<variablelist>
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<varlistentry>
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<term>GInputStream</term>
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<listitem><para>read data</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GOutputStream</term>
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<listitem><para>write data</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GSeekable</term>
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<listitem><para>interface optionally implemented by streams to support seeking</para></listitem>
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</varlistentry>
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</variablelist>
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There are interfaces related to applications and the types
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of files they handle:
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<variablelist>
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<varlistentry>
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<term>GAppInfo</term>
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<listitem><para>information about an installed application</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>GIcon</term>
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<listitem><para>abstract type for file and application icons</para></listitem>
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</varlistentry>
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</variablelist>
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Beyond these, GIO provides facilities for file monitoring,
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asynchronous I/O and filename completion. In addition to the
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interfaces, GIO provides implementations for the local case.
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Implementations for various network file systems are provided
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by the GVFS package as loadable modules.
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</para>
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<para>
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Other design choices which consciously break with the GnomeVFS
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design are to move backends out-of-process, which minimizes the
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dependency bloat and makes the whole system more robust. The backends
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are not included in GIO, but in the separate GVFS package. The GVFS
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package also contains the GVFS daemon, which spawn further mount
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daemons for each individual connection.
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</para>
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<figure id="gvfs-overview">
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<title>GIO in the GTK+ library stack</title>
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<graphic fileref="gvfs-overview.png" format="PNG"></graphic>
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</figure>
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<para>
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The GIO model of I/O is stateful: if an application establishes e.g.
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a SFTP connection to a server, it becomes available to all applications
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in the session; the user does not have to enter his password over
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and over again.
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</para>
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<para>
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One of the big advantages of putting the VFS in the GLib layer
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is that GTK+ can directly use it, e.g. in the filechooser.
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</para>
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</chapter>
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<chapter>
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<title>Compiling GIO applications</title>
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<para>
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GIO comes with a <filename>gio-2.0.pc</filename> file that you
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should use together with <literal>pkg-config</literal> to obtain
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the necessary information about header files and libraries. See
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the <literal>pkg-config</literal> man page or the GLib documentation
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for more information on how to use <literal>pkg-config</literal>
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to compile your application.
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</para>
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<para>
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If you are using GIO on UNIX-like systems, you may want to use
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UNIX-specific GIO interfaces such as #GUnixInputStream,
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#GUnixOutputStream, #GUnixMount or #GDesktopAppInfo.
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To do so, use the <filename>gio-unix-2.0.pc</filename> file
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instead of <filename>gio-2.0.pc</filename>
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</para>
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</chapter>
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</part>
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