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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> Saving Configuration Information </title> <meta name="GENERATOR" content= "Modular DocBook HTML Stylesheet Version 1.45"> <link rel="HOME" title="GTK+ / Gnome Application Development" href="ggad.html"> <link rel="UP" title="Gnome Application Basics" href= "cha-startup.html"> <link rel="PREVIOUS" title="Argument Parsing with popt" href= "z77.html"> <link rel="NEXT" title="Session Management" href= "sec-sessionmanagement.html"> </head> <body bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink= "#840084" alink="#0000FF"> <div class="NAVHEADER"> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <th colspan="4" align="center"> <font color="#000000" size="2">GTK+ / Gnome Application Development</font> </th> </tr> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="z77.html"><font color="#0000ff" size="2"><b> <<< Previous</b></font></a> </td> <td width="25%" colspan="2" bgcolor="#ffffff" align= "center"> <font color="#0000ff" size="2"><b><a href="ggad.html"> <font color="#0000ff" size="2"><b> Home</b></font></a></b></font> </td> <td width="25%" bgcolor="#ffffff" align="right"> <a href="sec-sessionmanagement.html"><font color= "#0000ff" size="2"><b>Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="Z79">Saving Configuration Information</a> </h1> <p> <tt class="APPLICATION">libgnome</tt> comes with the ability to store simple key-value pairs in plain text configuration files. Convenience routines are provided for numeric and boolean types which transparently convert to and from a text representation of each type. The standard location for Gnome configuration files is <tt class= "FILENAME">~/.gnome</tt>, and the library will use that location by default. However, the library can be used with any file. There are also variants of each function which save to <tt class="FILENAME">~/.gnome_private</tt>, a directory with user permissions only. The basic functions to store and retrieve data are listed in <a href= "z79.html#STARTUP-GNOMECONFIGGET">Figure 4 in the section called <i>Reading Stored Config Data</i></a> and <a href= "z79.html#STARTUP-GNOMECONFIGSET">Figure 5 in the section called <i>Storing Data In Configuration Files</i></a>. This module of <tt class="APPLICATION">libgnome</tt> is often referred to as <tt class="APPLICATION">gnome-config</tt>. Don't confuse this usage of "gnome-config" with the <tt class="APPLICATION">gnome-config</tt> script that reports the compile and link flags for Gnome programs. </p> <p> The <tt class="APPLICATION">gnome-config</tt> functions work with a <i class="FIRSTTERM">path</i>. A path has three components: </p> <ul> <li> <p> The <i class="FIRSTTERM">filename</i> to use, underneath the <tt class="FILENAME">~/.gnome</tt> or <tt class="FILENAME">~/.gnome_private</tt> directory. By convention this is the name of your application. </p> </li> <li> <p> A <i class="FIRSTTERM">section</i>---a logical subcategory of related configuration information. </p> </li> <li> <p> A <i class="FIRSTTERM">key</i>---the key half of a key-value pair. The key is actually associated with a piece of configuration data. </p> </li> </ul> <p> A path is passed to Gnome as a string, with the form <tt class="APPLICATION">"/filename/section/key"</tt>. If you want to use a filename which is <i class="EMPHASIS">not</i> in the standard Gnome directories, you can bracket the entire path with the <tt class="APPLICATION">'='</tt> character and it will be interpreted as absolute. You can even use this as a simple datafile format (it is used for the <tt class="APPLICATION">.desktop</tt> files programs install in order to appear on the Gnome panel menu). However, XML (perhaps using the <tt class="APPLICATION"> gnome-xml</tt> package) is almost certainly a better choice for that. XML may also be a better choice for storing some kinds of configuration information; the primary advantage of the <tt class="APPLICATION">libgnome</tt> configuration library is its simplicity. </p> <p> <tt class="APPLICATION">gnome-config</tt> has a long history; it was first written for the WINE Windows emulator project, then used in the GNU Midnight Commander file manager, and finally migrated into the Gnome libraries. The plan is to replace <tt class="APPLICATION"> gnome-config</tt> with something more powerful in the next version of Gnome; we want to support per-host configuration, backends such as LDAP, and other features. However, the <tt class="APPLICATION">gnome-config</tt> API will almost certainly be supported even if the underlying engine changes dramatically. </p> <div class="SECT2"> <h2 class="SECT2"> <a name="Z80">Reading Stored Config Data</a> </h2> <p> Retrieving data from files is simple. You simply call a function to retrieve the value for a given key. The value-retrieving functions (shown in <a href= "z79.html#STARTUP-GNOMECONFIGGET">Figure 4</a>) accept a path as their argument. For example, you might ask whether the user wants to see a dialog box: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gboolean show_dialog; show_dialog = gnome_config_get_bool("/myapp/General/dialog"); </pre> </td> </tr> </table> <p> If the config file doesn't exist yet, or there is no key matching the path you provide, these functions return 0, <span class="STRUCTNAME">FALSE</span>, or <span class= "STRUCTNAME">NULL</span>. The functions that return a string return allocated memory; you should <tt class= "FUNCTION">g_free()</tt> the returned string. The string vector functions return an allocated vector full of allocated strings (<tt class="FUNCTION">g_strfreev()</tt> is the easiest way to free this vector). </p> <p> You can specify a default value to be returned if the key does not exist; to do so, append an <span class= "STRUCTNAME">"=value"</span> to the path. For example: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gboolean show_dialog; show_dialog = gnome_config_get_bool("/myapp/General/dialog=true"); </pre> </td> </tr> </table> <p> Each function has a <span class="STRUCTNAME"> with_default</span> variant; these tell you whether the return value was taken from a config file or from the default you specified. For example: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gboolean show_dialog; gboolean used_default; show_dialog = gnome_config_get_bool_with_default("/myapp/General/dialog=true", &used_default); if (used_default) printf("Default value used for show_dialog\n"); </pre> </td> </table> <p> <tt class="FUNCTION">gnome_config_push_prefix()</tt> and <tt class="FUNCTION">gnome_config_pop_prefix()</tt> (in <a href="z79.html#STARTUP-GNOMECONFIGMISC">Figure 7 in the section called <i>Other Config File Operations</i></a>) can be used to avoid specifying the entire path each time. For example: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gboolean show_dialog; gnome_config_push_prefix("/myapp/General/"); show_dialog = gnome_config_get_bool("dialog=true"); gnome_config_pop_prefix(); </pre> </td> </tr> </table> <p> These functions also work when saving values. </p> <p> The configuration functions with <span class= "STRUCTNAME">private</span> in their name use a <tt class="FILENAME">.gnome_private</tt> directory with restricted permissions, as discussed above. The <span class="STRUCTNAME">translated_string</span> functions qualify the provided key with the name of the current locale; these are used when Gnome reads <tt class= "APPLICATION">.desktop</tt> files (see <a href= "z72.html#SEC-.DESKTOP">the section called <i><tt class= "APPLICATION">.desktop</tt> Entries</i> in the chapter called <i>Creating Your Source Tree</i></a>) and are probably not useful to applications. </p> <div class="FIGURE"> <a name="STARTUP-GNOMECONFIGGET"></a> <div class="FUNCSYNOPSIS"> <a name="STARTUP-GNOMECONFIGGET.SYNOPSIS"></a> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="FUNCSYNOPSISINFO">#include <libgnome/gnome-config.h></pre> </td> </tr> </table> <p> <code><code class="FUNCDEF">gchar* <tt class= "FUNCTION">gnome_config_get_string</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gchar* <tt class= "FUNCTION"> gnome_config_get_translated_string</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gint <tt class= "FUNCTION">gnome_config_get_int</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gdouble <tt class= "FUNCTION">gnome_config_get_float</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gboolean <tt class= "FUNCTION">gnome_config_get_bool</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">void <tt class= "FUNCTION">gnome_config_get_vector</tt></code>(const gchar* <tt class="PARAMETER"><i>path</i></tt>, gint* <tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt class="PARAMETER"><i>argvp</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gchar* <tt class= "FUNCTION"> gnome_config_private_get_string</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gchar* <tt class= "FUNCTION"> gnome_config_private_get_translated_string</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gint <tt class= "FUNCTION"> gnome_config_private_get_int</tt></code>(const gchar* <tt class="PARAMETER"><i>path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gdouble <tt class= "FUNCTION"> gnome_config_private_get_float</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gboolean <tt class= "FUNCTION"> gnome_config_private_get_bool</tt></code>(const gchar* <tt class="PARAMETER"><i> path</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">void <tt class= "FUNCTION"> gnome_config_private_get_vector</tt></code>(const gchar* <tt class="PARAMETER"><i>path</i></tt>, gint* <tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt class="PARAMETER"><i>argvp</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">gchar* <tt class= "FUNCTION"> gnome_config_get_string_with_default</tt></code>(const gchar* <tt class="PARAMETER"><i>path</i></tt>, gboolean* <tt class="PARAMETER"><i> was_default</i></tt>);</code>?? 快捷鍵說明
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