]>

<book id="index" lang="zh-CN">

<title>GNOME 辅助功能开发者指南</title>

<bookinfo>

<abstract role="description">

<para>GNOME 辅助功能指南是为那些想确保自己的程序能为更广泛的用户使用的开发人员准备的。本指南同时涵盖了许多第508节的要求。</para>

</abstract>

<copyright><year>2008</year> <holder>Vincent Alexander</holder></copyright>

<copyright><year>2001, 2002</year> <holder>Calum Benson, Brian Cameron, Bill Haneman, Padraig O'Briain, Sharon Snider</holder></copyright>

<publisher role="maintainer"> 

<publishername>GNOME 文档项目</publishername> 

</publisher>

<legalnotice id="legalnotice">

<para>在自由软件基金会发表的 GNU 自由文档许可证(GFDL)条款的约束下，此文档可以复制、分发和修改。许可证版本应为 1.1 或更新，章节应未加篡改，封面未经涂写。您可以从<ulink type="help" url="ghelp:fdl"> 这里</ulink>下载一份 GFDL，或从本手册附带的 COPYING-DOCS 文件中获取它。</para>

<para>此手册是 GNOME 手册系列的一部分，依照 GFDL 发布。如果想单独分发此手册，您需要向手册添加一份许可证协议，如许可证第 6 节所述。</para>

<para>许多名字被各公司注册为商标，以区别它们的产品和服务。任何 GNOME 文档中出现这些名字时，Gnome 文档项目作者都对它们加以留意，将其全名大写或首字母大写。</para>

<para>DOCUMENT AND MODIFIED VERSIONS OF THE DOCUMENT ARE PROVIDED UNDER THE TERMS OF THE GNU FREE DOCUMENTATION LICENSE WITH THE FURTHER UNDERSTANDING THAT: <orderedlist>

<listitem>

<para>DOCUMENT IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES THAT THE DOCUMENT OR MODIFIED VERSION OF THE DOCUMENT IS FREE OF DEFECTS MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE OR NON-INFRINGING. THE ENTIRE RISK AS TO THE QUALITY, ACCURACY, AND PERFORMANCE OF THE DOCUMENT OR MODIFIED VERSION OF THE DOCUMENT IS WITH YOU. SHOULD ANY DOCUMENT OR MODIFIED VERSION PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT THE INITIAL WRITER, AUTHOR OR ANY CONTRIBUTOR) ASSUME THE COST OF ANY NECESSARY SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. NO USE OF ANY DOCUMENT OR MODIFIED VERSION OF THE DOCUMENT IS AUTHORIZED HEREUNDER EXCEPT UNDER THIS DISCLAIMER; AND</para>

</listitem>

<listitem>

<para>UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL THEORY, WHETHER IN TORT (INCLUDING NEGLIGENCE), CONTRACT, OR OTHERWISE, SHALL THE AUTHOR, INITIAL WRITER, ANY CONTRIBUTOR, OR ANY DISTRIBUTOR OF THE DOCUMENT OR MODIFIED VERSION OF THE DOCUMENT, OR ANY SUPPLIER OF ANY OF SUCH PARTIES, BE LIABLE TO ANY PERSON FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER DAMAGES OR LOSSES ARISING OUT OF OR RELATING TO USE OF THE DOCUMENT AND MODIFIED VERSIONS OF THE DOCUMENT, EVEN IF SUCH PARTY SHALL HAVE BEEN INFORMED OF THE POSSIBILITY OF SUCH DAMAGES.</para>

</listitem>

</orderedlist></para>

</legalnotice>

<authorgroup> 

<author><firstname>Vincent</firstname> <surname>Alexander</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author>

<author><firstname>Calum</firstname> <surname>Benson</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author>

<author><firstname>Brian</firstname> <surname>Cameron</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author>

<author><firstname>Bill</firstname> <surname>Haneman</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author>

<author><firstname>Padraig</firstname> <surname>O'Briain</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author> 

<author><firstname>Sharon</firstname> <surname>Snider</surname> <affiliation> <orgname>GNOME 文档项目</orgname> </affiliation></author>

</authorgroup>

<revhistory>

<revision><revnumber> GNOME 2.24 辅助功能开发者指南 V2.24.0 </revnumber> <date>2008年9月</date> <revdescription> 

<para role="author">GNOME 文档项目</para> 

<para role="publisher">GNOME 文档项目</para> 

</revdescription></revision>

<revision><revnumber> GNOME 2.24 辅助功能开发者指南 V2.24.0 </revnumber> <date>2008年9月</date> <revdescription> 

<para role="author">GNOME 文档项目</para> 

<para role="publisher">GNOME 文档项目</para> 

</revdescription></revision>

</revhistory>

<releaseinfo>本手册描述 GNOME 2.24 桌面。</releaseinfo>

<legalnotice> 

<title>反馈</title> 

<para>报告 bug 或者为 GNOME 桌面和本手册提供建议, 请点击 <ulink type="help" url="ghelp:user-guide?feedback">GNOME 反馈页面</ulink>.</para>

</legalnotice> 

    <othercredit class="translator">

      <personname>

        <firstname>keyring</firstname>

      </personname>

      <email>keyrings@163.com</email>

    </othercredit>

    <copyright>

        <year>2013</year>

      <holder>keyring</holder>

    </copyright>

  </bookinfo>

<chapter id="gad" status="draft">

<title>什么是辅助功能？</title>

<para>辅助功能是指协助残疾人士参与大量日常活动，包括日常工作以及服务、产品、资讯的使用。GNOME 包含一系列库与支持框架能让残疾人士使用 GNOME 用户环境的所有功能。</para>

<para>因此，必要时综合利用辅助技术——语音接口，屏幕阅读器，复用输入设备等等——可以帮助那些永久性或暂时性残疾人士便捷地使用 GNOME 桌面和应用程序。辅助技术对那些不在家里或办公室中使用电脑的人也非常有用。比如，如果你被堵在车流之中，你可以使用语音输入和输出来查阅你的电子邮件。</para>

<para>辅助技术通过使用辅助工具包 (ATK) 的 API 接收来自应用程序的信息，ATK 可以在 GNOME 仓库中找到。由于辅助 API 内置到了 GNOME 的 widgets 中，所以你不需做额外工作就可以让你的 GNOME 程序合理运行在辅助技术上。例如，辅助技术能够自动读取你设置在程序中的部件的标签（比如 GTK 的函数调用：<function>gtk_label_set_text()</function> 或者 <function>gtk_button_new_with_label()</function>）。它们也能找到与某个部件相关联的任何提示文本，然后使用该文本来向用户描述那个部件。</para>

<para>当然，你也可以多花点心思，利用辅助技术来让你的程序运行的更加流畅。这除了可以帮助个人用户，也可以让你的产品在政府部门和教育市场中更具吸引力，因为如今法律要求这个领域的很多应用必须得无障碍。</para>

<section>

<title>残疾类型</title>

<para>仅在美国，大约有3000万人因为不合理设计而无法便利使用电脑。在全球范围下，大约有8%的互联网使用者有不同程度的残疾。残疾可分为以下几种：</para>

<itemizedlist>

<listitem>

<para><emphasis>视觉障碍 </emphasis>——包括弱视（视力昏暗模糊，远/近视，色盲和视力狭窄）到完全失明。一些糟糕的文本字体颜色选择和需要手眼协调的任务（比如移动鼠标）都可能为这些用户造成困难。</para>

</listitem>

<listitem>

<para><emphasis>运动障碍 </emphasis>——肌肉控制力差或虚弱到不足以使用标准键鼠。例如，他们可能无法同时按住两个键，或者更容易意外按错。</para>

</listitem>

<listitem>

<para><emphasis>听觉障碍 </emphasis>—— 包括弱听而听不懂到完全失聪。那些单靠声音来传达重要信息的应用程序会对这部分用户造成困难。</para>

</listitem>

<listitem>

<para><emphasis>认知与语言障碍 </emphasis>——包括阅读障碍与记忆障碍，只靠说写来处理与理解事物。复杂或不一致的显示，或者拙劣的词汇选择都会造成这部分用户使用电脑困难。</para>

</listitem>

<listitem>

<para><emphasis>癫痫疾病</emphasis>——对一些敏感的用户，某些光或声音会造成癫痫发作。</para>

</listitem>

</itemizedlist>

</section>

<section id="gad-how-it-works">

<title>辅助功能在 GNOME 中如何工作</title>

<para>辅助工具包 (ATK) 描述了一组接口，要访问它们就需要通过 GUI 组件自行实现。这些接口是工具包无关的，意思就是你可以用任意部件集来实现，比如 GTK，Motif 或者 Qt 。</para>

<para>

The implementation for the GTK widgets is in a module called GAIL (GNOME Accessibility Implementation Library), which is dynamically loadable at runtime by a GTK application. Once

loaded, those parts of your application that use standard GTK widgets will have a basic level of accessibility, without you having to modify your application at all. If GAIL is not

loaded, GTK widgets will have a default accessibility implementation that essentially returns no information, though it nominally conforms to the ATK API. Applications which use

Bonobo controls, particularly out-of-process ones, also load accessibility support code from module libgail-gnome. Whether or not applications on the GNOME desktop automatically load these accessibility support libraries depends on the value of a <application>gconf</application> key, "/desktop/gnome/interface/accessibility"; a boolean value of "true" enables support for assistive technologies and applications which call gnome_program_init will automatically load the appropriate accessibility libraries at runtime. "Pure GTK+ applications", e.g. those that use gtk+ but do not link to libgnome, rely on the value of the GTK_MODULES environment variable, which must be set to "gail:atk-bridge" in order to enable assistive technology support.

</para>

<para>长久以来，大部分其他桌面平台所使用的辅助技术必须为桌面应用维护一个复杂的离屏模式，这种模式基于对操作系统事件的监听，使用不受支持的操作系统、应用程序特性和 API，还有一些其他高度不可移植的技术。这就使得辅助技术支持有点 "不健壮"，需要特定的操作系统和指定的应用程序，甚至还要指定的应用程序版本。相反，在 GNOME 桌面，通过 GNOME 辅助功能框架，使用服务提供者接口（SPI）独立工具包，AT（辅助技术） 需要的所有信息均可由运行的应用程序提供。SPI 为基于 UNIX 的 AT 提供一些内置服务，比如屏幕阅读器和屏幕放大镜。通过一致而稳定的 API 从运行的程序中获取辅助信息，可以在大多数情况下避免使用离屏模式。对应用程序的辅助功能支持一般通过合适的 API （比如，ATK 多用于原生C程序而Java辅助 API 用于Java 应用）内置在应用程序工具包中，然后通过相应的 "bridge" 导出成通用 "AT-SPI" 接口（见下图）。</para>

<figure id="gad-architecture">

<title>GNOME 辅助功能架构</title>

<mediaobject><imageobject> <imagedata fileref="figures/GNOME_desktop_Accessibility.png" format="PNG"/> </imageobject> <textobject> <phrase> GNOME 辅助功能架构图解</phrase> </textobject></mediaobject>

</figure>

<para>GNOME 内置辅助功能支持意味着使用 GNOME 部件创建应用程序可以 "免费" 获得辅助技术的支持，而不用额外使用与内置支持相冲突的迂回方法。</para>

<para>如果一个 gtk+/GNOME 部件遵循本文档中的普遍辅助指南，实现了 ATK 接口并在用户界面上扮演合适的角色，则它是具有辅助性的。 ATK 的执行由 "stock" GNOME 部件工具集提供，而且大多数情况下，由现有 GTK+/GNOME 部件派生出来的新部件同时也会继承合适的辅助功能支持。</para>

<para>

Though GNOME's built-in accessibility support provides significant functionality without any accessibility-specific code changes on the part of the application, applications can often improve on the default descriptions provided for some of the widgets, and tailor them to that widget's specific purpose in your application, via straightforward calls to ATK methods in the application. For instance, in most cases applications should add or change the textual descriptions for these widgets with the appropriate ATK function call, so that an assistive technology can describe their purpose or state to the user. See <link linkend="gad-coding-guidelines">Coding Guidelines for Supporting Accessibility</link> for more information.

</para>

<para>如果你的程序使用自定义部件，可能需要做些工作让它们得以使用辅助技术。参阅 <link linkend="gad-custom"> 让自定义组件获得辅助功能 </link> 和 <link linkend="gad-api-examples"> 使用辅助 API 的示例 </link> 获取更多信息。</para>

<para>此外，关于 GTK/GTK+ 更多深入内容，请参阅 <ulink url="http://library.gnome.org/devel/gtk"> GTK+ 参考手册 </ulink>, <ulink url="http://live.gnome.org/GAP/AtkGuide/Gtk">ATK 指南的 GTK 章节</ulink>, GNOME 网站托管的 <ulink url="http://library.gnome.org/devel/gtk-tutorial/stable/">GTK+ 2.0 教程</ulink> 和官方 <ulink url="http://library.gnome.org/devel/gtk-faq/stable/">GTK+ FAQ</ulink>。</para>

</section>

<section id="dev-start">

<title>开发者快速指南</title>

<para>这有一些常用出发点：</para>

<section id="dev-start-1">

<title>如何确定应用程序是否具有辅助功能？</title>

<para>

To start right in, see <link linkend="gad-overview">Making a GNOME Application Accessible - Overview</link>. For a pre-coding perspective, see <link linkend="gad-ui-guidelines">User Interface Guidelines for Supporting Accessibility</link> or <link linkend="gad-coding-guidelines">Coding Guidelines for Supporting Accessibility</link>. For a checklist of post-design test items, see <link linkend="gad-checklist">User Interface Checklist</link>.

</para>

</section>

<section id="dev-start-2">

<title>有哪些常见陷阱？</title>

<para><link linkend="gad-checklist">用户界面审查清单</link>涵盖了所有设计阶段容易被忽略的地方。</para>

</section>

<section id="dev-start-3">

<title>如何实现常见的 ATK 功能？</title>

<para>可以在<link linkend="gad-api">这里</link>找到一份常见 ATK 调用的简短列表。</para>

</section>

<section id="dev-start-4">

<title>如何实现更复杂的 ATK 功能？</title>

<para>参考 <link linkend="gad-custom"> 让自定义组件获得辅助功能 </link> 和 <link linkend="gad-api-examples"> 使用辅助功能 API 的示例 </link>来获取更多信息。</para>

</section>

<section id="dev-start-5">

<title>ATK,、AT-SPI、 GAIL 和 GTK+ 介绍</title>

<screenshot>

<mediaobject><imageobject> <imagedata fileref="figures/gaa.jpg"/> </imageobject> <textobject> <phrase> GNOME 辅助功能架构 </phrase> </textobject></mediaobject>

</screenshot>

<para>ATK 工具包可以提供额外辅助功能支持让 GNOME 使用者充分利用电脑。ATK 用于诸如屏幕阅读器、放大镜和输入设备等工具来允许通过其他方式与桌面进行富交互。详情可参阅 <ulink url="http://java-gnome.sourceforge.net/4.0/doc/api/org/gnome/atk/package-summary.html"> ATK SourceForge 的项目 </ulink> 和 <ulink url="http://library.gnome.org/devel/atk/stable/">ATK 库</ulink>。</para>

<para>AT-SPI 是基础服务接口，用于辅助技术查询和接收来自正在运行的程序的通知。全部 API 可以查阅 <ulink url="http://library.gnome.org/devel/at-spi-cspi/stable/">here</ulink>。额外材料可参阅 <ulink url="http://accessibility.kde.org/developer/atk.php#coreclasses"> KDE 辅助功能开发者社区 </ulink>。</para>

<para>GAIL (GNOME Accessibility Implementation Library) 是 ATK 辅助功能接口的默认实现。GTK 工具集早已通过 GAIL 模块与 ATK 进行了绑定。许可条款、下载中心和其他信息可参阅 <ulink url="http://www.t2-project.org/packages/gail.html"> 这里 </ulink>。<ulink url="ftp://ftp.gnome.org/pub/GNOME/sources/gail/"> GAIL 源码 </ulink> 也提供了一份出色的教程来说明 ATK 的高级用法。此外，你也可能对 <ulink url="http://library.gnome.org/devel/gail-libgail-util/stable/"> GAIL 参考手册 </ulink>感兴趣。</para>

<para>GTK+ 是个创建图形用户界面的 UI 库。可运行于多种类UNIX平台、Windows和基于帧缓存的设备。GTK+ 在 GNU Library General Public License (GNU LGPL)许可下发行。</para>

<para>此外，关于 GTK/GTK+ 更多深入内容，请参阅 <ulink url="http://library.gnome.org/devel/gtk">GTK+ 参考手册</ulink>,<ulink url="http://wiki.gnome.org/Accessibility/Documentation/GNOME2/AtkGuide/Gtk">ATK 指南的 GTK+ 章节</ulink>, GNOME 网站托管的<ulink url="http://library.gnome.org/devel/gtk-tutorial/stable/">GTK+ 2.0 教程</ulink> 和官方<ulink url="http://library.gnome.org/devel/gtk-faq/stable/">GTK+ FAQ</ulink>。</para>

</section>

</section>

<section id="gad-overview">

<title>让一个 GNOME 应用程序具有辅助功能 - 综述</title>

<para>如果你的应用程序只使用标准 GTK 部件，你可以做很少甚至不做任何事情就能让程序获得（适当的）辅助功能。但要注意那些没有文字说明的GUI对象，比如没有文本标签的图形按钮或者没有工具提示信息的状态指示器。</para>

<para>

You can probably also improve on the default descriptions provided for some of the widgets, and tailor them to that widget's specific purpose in your application. You should add or change the textual descriptions for these widgets with the appropriate ATK function call, so that an assistive technology can describe their purpose or state to the user. See <link linkend="gad-coding-guidelines">Coding Guidelines for Supporting Accessibility</link> for more information.

</para>

<para>如果你的程序使用自定义部件，可能需要做些工作以使这些部件利用辅助技术。参阅 <link linkend="gad-custom"> 让自定义组件获得辅助功能 </link> 和 <link linkend="gad-api-examples"> 使用辅助功能 API 的示例</link> 获取更多信息。更多详细内容也可参见 Marc Mulcahy 的 2002 GUADEC 演示文档, <ulink url="https://projects.gnome.org/accessibility/talks/GUAD3C/making-apps-accessible/start.html">“制作具有辅助功能的 GNOME 应用程序”。</ulink></para>

</section>

<section id="gad-coding-guidelines">

<title>获取辅助功能的编程指南</title>

<para>这里列出了一些可以在代码里做的事情，让程序更好的利用辅助技术。（当你想设计GUI的时候，可以看看后文里提到的这份列表 <link linkend="gad-ui-guidelines"> 支持辅助功能的UI </link>）：</para>

<itemizedlist>

<listitem>

<para>用于那些不显示短字符串的组件（比如图形按钮），使用 <function>atk_object_set_name()</function>为它指定一个名字。你可以用于纯图片按钮、具有逻辑分组的面板、文本区域等等。</para>

</listitem>

<listitem>

<para>如果你没有为组件提供提示信息，使用 <function>atk_object_set_description()</function> 函数为用户提供一个辅助说明。例如，为一个 <guibutton> 关闭 </guibutton>按钮提供辅助说明：</para>

<example>

<title>为 GtkButton 提供辅助性说明</title>

<programlisting>

{

  AtkObject *obj;

  obj = gtk_widget_get_accessible(button);

  atk_object_set_description(obj,_("Closes the window"));

}

</programlisting>

</example>

</listitem>

<listitem>

<para>使用 <function>atk_image_set_description()</function> 可以为程序中所有图片图标提供一个文本说明。</para>

</listitem>

<listitem>

<para>如果多个组件逻辑上是一组的，建议将它们放在一个容器里。</para>

</listitem>

<listitem>

<para>

Whenever you have a label that describes another component, use <function>atk_relation_set_add_relation()</function> so that assistive technologies can find the component with which the label is associated. (If you associate the label with the component using <function>gtk_label_set_mnemonic_widget()</function>, the <constant>ATK_RELATION_LABEL_FOR</constant> relation is generated automatically, so the following code would not be necessary):

</para>

<example>

<title>为一个 GtkWidget 关联一个 GtkLabel</title>

<programlisting>

{

  GtkWidget *widget;

  GtkLabel *label;

  AtkObject *atk_widget, *atk_label;

  AtkRelationSet *relation_set;

  AtkRelation *relation;

  AtkObject *targets[1];

  atk_widget = gtk_widget_get_accessible(widget);

  atk_label = gtk_widget_get_accessible (GTK_WIDGET(label));

  relation_set = atk_object_ref_relation_set (atk_label);

  targets[0] = atk_widget;

  relation = atk_relation_new(targets,1, ATK_RELATION_LABEL_FOR);

  atk_relation_set_add(relation_set,relation);

  g_object_unref(G_OBJECT(relation));

}

</programlisting>

</example>

</listitem>

<listitem>

<para>如果创建了一个自定义 widget，要确认是否支持辅助功能。自定义组件通常继承于其他 GTK 部件，所以必要时得重写辅助功能信息。更多信息请参考 <link linkend="gad-custom"> 让自定义组件获得辅助功能 </link>。</para>

</listitem>

<listitem>

<para>不要重复造轮子！如果你的 GUI 有一个非辅助性的容器，那么该容器内的任何组件都可能失去辅助性。</para>

</listitem>

</itemizedlist>

</section>

<section id="gad-api">

<title>辅助功能 API</title>

<para>这里是一部分基础 API 调用，你可以用来确认程序是否利用辅助技术并工作良好。全部的辅助功能 API 非常全面，比如可以让你写出自定义辅助部件。</para>

<title>常用 ATK API 调用</title>

<tgroup cols="2" align="left">

<row>

<entry>API</entry>

<entry>描述</entry>

</row>

<row>

<entry>

<para><function>AtkObject* gtk_widget_get_accessible (GtkWidget*)</function></para>

</entry>

<entry>

<para>

Returns the accessible object that describes the specified GTK widget to an assistive technology.

</para>

</entry>

</row>

<row>

<entry>

<para><function>void atk_object_set_name (AtkObject*, const gchar*)</function></para>

</entry>

<entry>

<para>为辅助对象命名。例如，如果对象是个图形按钮，按下会使得程序退出，那你可以为它命名为 "退出"。</para>

</entry>

</row>

<row>

<entry>

<para><function>void atk_object_set_description (AtkObject*, const gchar*)</function></para>

</entry>

<entry>

<para>为辅助对象设置文字说明。例如，如果对象是个图形化的"关闭"按钮，那文字说明可以写成"关闭窗口"。</para>

</entry>

</row>

<row>

<entry>

<para><function>AtkRelation* atk_relation_new (AtkObject**, gint, AtkRelationType)</function></para>

</entry>

<entry>

<para>在指定的键与指定的目标对象列表之间创建一个新的关系。这个关系通常指的是一个部件以某种方式关联到另一个之间的辅助技术。例如，同一个窗口下，有一个特定的 GtkLabel 才是 GtkTreeView 的标题。</para>

</entry>

</row>

<row>

<entry>

<para><function>void atk_image_set_description (AtkImage*, const gchar*)</function></para>

</entry>

<entry>

<para>为图片辅助对象设置文字说明。例如，如果对象是面板内的一个虚拟桌面的缩略图，这个文字说明可以写成 "桌面 1 内的窗口排列图"。</para>

</entry>

</row>

</tgroup>

</section>

<section id="gad-api-examples">

<title>使用辅助功能 API 的示例</title>

<para>前文提过，如果使用标准 GTK 部件或者任何其他实现了 ATK 接口的部件库，你可以只做一点甚至不做任何事情就可以让你的应用程序获得辅助功能。这样的话，通常只需做两件事：</para>

<itemizedlist>

<listitem>

<para>使用 <function>atk_object_set_description()</function> 或者 <function>atk_image_set_description():</function> 为控件和图片提供文字说明</para>

<example>

<title>为按钮设置辅助功能说明</title>

<programlisting>

{

   AtkObject *obj;

   obj = gtk_widget_get_accessible(button);

   atk_object_set_description(obj,_("Opens Preferences dialog"));

}

</programlisting>

</example>

<para>

</para>

</listitem>

<listitem>

<para>使用 <function>atk_relation_new()</function> and <function>atk_relation_set_add()</function> 在任意特殊组合中的部件之间指定关系</para>

<example>

<title>在两个控件之间指定辅助关系</title>

<programlisting>

{

  GtkWidget *widget;

  GtkLabel *label;

  AtkObject *atk_widget, *atk_label;

  AtkRelationSet *relation_set;

  AtkRelation *relation;

  AtkObject *targets[1];

  atk_widget = gtk_widget_get_accessible (widget);

  atk_label = gtk_widget_get_accessible (GTK_WIDGET(label));

  relation_set = atk_object_ref_relation_set (atk_label);

  targets[0] = atk_widget;

  relation = atk_relation_new(targets,1, ATK_RELATION_LABEL_FOR);

  atk_relation_set_add(relation_set,relation);

  g_object_unref(G_OBJECT(relation));

}

</programlisting>

</example>

</listitem>

</itemizedlist>

<para>

The examples in the rest of this section are mostly to give you a flavor of the scope of the ATK. They cover techniques that you may never need to use as an application developer, although they may be of interest if you are writing your own custom widgets (see <link linkend="gad-custom">Making Custom Components Accessible</link>) or if you want to write an assistive technology application. Whatever the purpose, the <ulink url="ftp://ftp.gnome.org/pub/GNOME/sources/gail/">GAIL source code</ulink> serves as an excellent tutorial for advanced ATK usage. Please note that since GTK+ 3.1.10, Gail has been merged into GTK+ and is no longer a module on its own.

</para>

<section>

<title>Gtk 模块</title>

<para>程序使用 GAIL（GTK 部件的辅助功能实现库）时，它会被当作 GTK 模块引入程序。GTK 模块在 <varname>GTK_MODULES</varname> 环境变量指定了模块名称时，会被加载到程序空间。如果有多个模块库，以冒号间隔。例如：</para>

<para><userinput>setenv GTK_MODULES "libgail:libtestprops"</userinput></para>

<para>所有 GTK 模块都有一个<function>gtk_module_init()</function> 函数。</para>

</section>

<section>

<title>收集一个应用程序的辅助信息</title>

<para>程序若想利用 ATK 调用，需要做下列一件（或以上）的事情：</para>

<orderedlist>

<listitem>

<para>创建一个事件监视器，比如使用 <function>atk_add_focus_tracker()</function> 函数：</para>

<programlisting>atk_add_focus_tracker (_my_focus_tracker);</programlisting>

<para> <function>_my_focus_tracker()</function> 函数原型：</para>

<programlisting>void _my_focus_tracker (AtkObject *aobject);</programlisting>

</listitem>

<listitem>

<para>建立一个全局事件监听器，使用 atk_add_global_event_listener()：</para>

<programlisting>

mouse_watcher_focus_id =   atk_add_global_event_listener(_my_global_listener,"Gtk:GtkWidget:enter_notify_event");

</programlisting>

<para><function>_my_global_listener</function> 拥有一个 Glib <type>GSignalEmissionHook</type> 原型。这个例子说明，一个 <type>GtkWidget</type> 对象无论何时触发一个 enter_notify_even 信号，都会调用 <function>_my_global_listener()</function>。</para>

</listitem>

<listitem>

<para>下列函数调用可以访问 ATK 顶层对象。</para>

<programlisting>AtkObject *root_obj = atk_get_root();</programlisting>

<para>

This returns an <type>AtkObject</type> which contains all toplevel windows in the currently running program. The user could then navigate through the object hierarchy by accessing the root object's children, which corresponds to the toplevel windows.

</para>

</listitem>

</orderedlist>

</section>

<section>

<title>查询一个 <type>AtkObject</type> 的接口</title>

<para>在程序中定位到具有辅助性 <type>AtkObject</type> 的对象后 (比如使用 <function>gtk_widget_get_accessible()</function>)，你可以用不同方式查到哪些接口已被实现：</para>

<orderedlist>

<listitem>

<para>可以使用提供的 <function>ATK_IS_...</function> 宏，例如：</para>

<itemizedlist>

<listitem>

<para><function>ATK_IS_ACTION(atkobj)</function></para>

</listitem>

<listitem>

<para><function>ATK_IS_COMPONENT(atkobj)</function></para>

</listitem>

<listitem>

<para>等等。（每个接口都有一个）</para>

</listitem>

</itemizedlist>

<para>如果宏返回 <function>TRUE</function>，则该接口可安全用于那个 ATK 对象上。</para>

</listitem>

<listitem>

<para>调用 <function>atk_object_get_role()</function> 来测试 <type>AtkObject</type> 的角色。任何已知角色均有一个指定数字对应 ATK API。</para>

</listitem>

</orderedlist>

</section>

<section>

<title>建立一个 ATK 信号处理函数</title>

<para>使用 <constant>column_inserted</constant> 信号来举例：</para>

<programlisting>

table_column_inserted_id = g_signal_connect_closure_by_id (my_atk_obj, 

g_signal_lookup("column_inserted", G_OBJECT_TYPE(my_atk_obj)), 0, 

g_cclosure_new(G_CALLBACK (_my_table_column_inserted_func), NULL, NULL), FALSE);

</programlisting>

<para>这会使无论何时  <type>AtkObject</type> <varname>my_atk_object</varname> 发出一个 column_inserted 信号，都会调用 <function>_my_table_column_inserted_func()</function>。</para>

<para>

Connecting to a signal is slightly different if the signal supports detail. The <constant>children_changed</constant> signal supports the <parameter>add</parameter> detail. To connect to a signal when the <parameter>add</parameter> detail is also specified, this technique is used:

</para>

<programlisting>

child_added_id = g_signal_connect_closure (my_atk_obj,"children_changed::add",

g_cclosure_new (G_CALLBACK(_my_children_changed_func), NULL, NULL), FALSE);

</programlisting>

<para>

This will cause <function>_my_children_changed_func()</function> to be called whenever a <constant>children_changed</constant> signal with the <parameter>add</parameter> detail is emitted on the <type>AtkObject</type> <varname>my_atk_obj</varname>.

</para>

</section>

<section>

<title>实现一个 ATK 对象</title>

<para>你可能需要为那些未在 GAIL（或者其他部件集中的同等库） 中实现辅助功能的部件亲自动手实现 ATK 对象。该实现应该作为一个 GTK 模块，而且要被包含在  <envar>GTK_MODULES</envar> 环境变量中，以使之在运行时被加载。</para>

<section>

<title>注册</title>

<para>这个例子中，我们假设一个对象叫 GTK_TYPE_MYTYPE，ATK 的实现叫 <type>MYATKIMP_TYPE_MYTYPE</type>，需要的工厂叫 <type>MYATKIMP_TYPE_MYTYPE_FACTORY</type>。</para>

<para>为 GTK 对象注册一个 ATK 实现，需要在模块的 <function>gtk_module_init()</function> 函数中做以下步骤：</para>

<orderedlist>

<listitem>

<para>访问默认注册表：</para>

<programlisting>

default_registry = atk_get_default_registry();

</programlisting>

</listitem>

<listitem><para>在该模块的 <function>gtk_module_init()</function>函数中注册 ATK 对象，函数调用如下：</para>

<programlisting>

atk_registry_set_factory_type (default_registry, GTK_TYPE_MYTYPE, 

MYATKIMP_TYPE_MYTYPE_FACTORY); 

</programlisting>

</listitem>

</orderedlist>

<para>这样将把 AtkObject 的实现 <type>GTK_TYPE_MYTYPE</type> 注册到 <type>MYATKIMP_TYPE_MYTYPE_FACTORY</type>中。工厂实现后就知道如何构建 <type>MYATKIMP_TYPE_MYTYPE</type>类型的对象了。</para>

</section>

<section>

<title>工厂</title>

<para>

The factory must be implemented as a child of class type <type>ATK_TYPE_OBJECT_FACTORY</type> and must implement the function <function>create_accessible()</function>. This function must create an appropriate <type>AtkObject</type>. A factory can be used to create more than one type of object, in which case its <function>create_accessible()</function> function will need to be smart enough to build and return the correct <type>AtkObject</type>.

</para>

</section>

<section>

<title>ATK Implementation for a Specific Object</title>

<para>所有 <type>GObject</type> 均要实现一个 <function>get_type()</function> 函数。使用上面的命名惯例将函数命名为 <function>myatkimp_mytype_get_type()</function>。</para>

<para>

In this function, you specify which interfaces your object implements. If the following logic were included in this <function>get_type()</function> function, this object would implement the <type>ATK_TEXT</type> interface:

</para>

<example>

<title> <function>get_type()</function> 函数示例</title>

<programlisting>

static const GInterfaceInfo atk_text_info = 

{ 

   (GInterfaceInitFunc) atk_text_interface_init, 

   (GInterfaceFinalizeFunc) NULL, 

   NULL 

}; 

g_type_add_interface_static (type, ATK_TYPE_TEXT, 

                             &atk_text_info); 

</programlisting>

</example>

<para>函数 <function>atk_text_interface_init()</function> 需要实现的函数原型如下：</para>

<programlisting>

void atk_text_interface_init (AtkTextIface *iface); 

</programlisting>

<para>

This function would connect the interface function calls to the specific implementation as follows:

</para>

<example>

<title>连接自定义接口与一个 AtkObject 实现</title>

<programlisting>

void 

atk_text_interface_init (AtkTextIface *iface) 

{ 

   g_return_if_fail (iface != NULL); 

   iface->get_text = myatkimp_mytype_get_text; 

   iface->get_character_at_offset = myatkimp_mytype_get_character_at_offset; 

   ... 

}

</programlisting>

</example>

<para>

Then the functions <function>myatkimp_mytype_get_text()</function>, <function>myatkimp_mytype_get_character_at_offset()</function>, and the rest of the <type>ATK_TEXT</type> interface functions would need to be implemented.

</para>

</section>

<section>

<title><type>AtkObject</type> 实现</title>

<para>

<type>AtkObject</type>s are <type>GObjects</type>, and all <type>GObject</type>s need to specify the <function>get_type()</function> function. Here is an example that sets up a class and instance initializer. This <function>get_type()</function> function also specifies that the object implements <type>ATK_TEXT</type> and specifies the parent object to be <type>MYATKIMP_MYPARENTTYPE</type>.

</para>

<example>

<title> <function>get_type()</function> 的实现示例</title>

<programlisting>

GType 

myatkimp_mytype_get_type (void) 

{ 

   static GType type = 0; 

   if (!type) 

   { 

      static const GTypeInfo tinfo = 

      { 

         sizeof (GailLabelClass), 

         (GBaseInitFunc) NULL,                              /* base init */ 

         (GBaseFinalizeFunc) NULL,                          /* base finalize */

         (GClassInitFunc) myatkimp_mytype_class_init,       /* class init */ 

         (GClassFinalizeFunc) NULL,                         /* class finalize */ 

         NULL,                                              /* class data */ 

         sizeof (GailLabel),                                /* instance size */ 

         0,                                                 /* nb preallocs */ 

         (GInstanceInitFunc) myatkimp_mytype_instance_init, /* instance init */ 

         NULL                                               /* value table */ 

      }; 

      /* Set up atk_text_info structure used below */ 

      static const GInterfaceInfo atk_text_info = 

      { 

         (GInterfaceInitFunc) atk_text_interface_init, 

         (GInterfaceFinalizeFunc) NULL, 

         NULL 

      }; 

      /* Set up typename and specify parent type */ 

      type = g_type_register_static (MYATKIMP_MYPARENTTYPE, 

            "MyatkimpMytype", &tinfo, 0); 

      /* This class implements interface ATK_TYPE_TEXT */ 

      g_type_add_interface_static (type, ATK_TYPE_TEXT, 

                                   &atk_text_info); 

   } 

   return type; 

} 

</programlisting>

</example>

</section>

<section>

<title>类/实例初始化</title>

<para>不管是 <type>GObject</type> 还是你自己的 <type>AtkObject</type> 实现，都得进行类初始化：</para>

<orderedlist>

<listitem>

<para>

Redefines any function calls defined by the object's parent. This is typically necessary when an object needs to implement a function like <function>atk_object_get_n_accessible_children()</function>.  This is necessary if the object has children, but they are not represented with widgets.

</para>

<para>

For example, if your ATK implementation needs to over-ride the <type>AtkObject</type> function <function>get_name()</function>, then the class initializer would look like:

</para>

<example>

<title>类初始化将覆写父类的 <function>get_name()</function> 函数</title>

<programlisting>

myatkimp_mytype_class_init (GailLabelClass *klass) 

{ 

  AtkObjectClass *class = ATK_OBJECT_CLASS (klass); 

  class->get_name = myatkimp_mytype_get_name; 

} 

</programlisting>

</example>

</listitem>

<listitem><para>Requires a <function>parent->init</function>, <function>parent->notify_gtk</function>, or <function>parent->finalize</function> function. This example defines all three:

</para>

<example>

<title>Class initializer that defines its own <function>init()</function>, <function>notify_gtk()</function> and <function>finalize()</function> functions</title>

<programlisting>

static ParentObjectType *parent_class = NULL; 

myatkimp_mytype_class_init (GailLabelClass *klass) 

{ 

   ParentObjectType *parent_class = (ParentObjectType*)klass; 

   /* 

    * Caching the parent_class is necessary if the init, 

    * notify_gtk, or finalize functions are set up. 

    */ 

    parent_class = g_type_class_ref (MYATKIMP_TYPE_PARENT); 

    parent_class->init = myatkimp_mytype_widget_init; 

    parent_class->notify_gtk = myatkimp_mytype_real_notify_gtk; 

    parent_class->finalize = myatkimp_mytype_finalize; 

}

</programlisting>

</example>

<orderedlist>

<listitem>

<para>parent->init</para>

<para>

A <function>parent->init()</function> function may be necessary if the ATK implementation needs to do either of the following:

</para> 

<orderedlist>

<listitem>

<para>

Cache any data obtained from a backing GTK widget.

</para>

</listitem>

<listitem>

<para>

Listen to any signals from the backing GTK widget.

</para>

</listitem>

</orderedlist>

<para>

Here is an example of both:

</para>

<example>

<title>自定义 <function>init()</function> 函数</title>

<programlisting>

void 

gail_tree_view_widget_init (MyatkimpMytype  *mytype, 

                            GtkWidget       *gtk_widget) 

{ 

   /* Make sure to call the parent's init function */ 

   parent_class->init (widget, gtk_widget); 

   /* Cache a value in the ATK implementation */ 

   mytype->cached_value = gtk_widget_function_call(); 

   /* Listen to a signal */ 

   gtk_signal_connect (GTK_OBJECT (gtk_widget), 

                       "signal-type", 

                       GTK_SIGNAL_FUNC (_myatkimp_mytype_signal_type), 

                       NULL); 

} 

</programlisting>

</example>

<para>

In this example, if the specified <type>signal-type</type> signal were generated on the backing <varname>gtk_widget</varname>, then the <function>_myatkimp_mytype_signal_type()</function> function would be called.

</para>

</listitem>

<listitem>

<para>parent->notify_gtk</para>

<para>

If the ATK implementation needs to listen to any property notifications on the backing GTK object, a <function>parent->notify_gtk()</function> function may be necessary. For example:

</para>

<example>

<title>自定义 <function>notify_gtk()</function> 函数</title>

<programlisting>

void 

myatkimp_mytype_real_notify_gtk (GObject    *obj, 

                                 GParamSpec *pspec) 

{ 

   GtkWidget *widget = GTK_WIDGET (obj); 

   AtkObject* atk_obj = gtk_widget_get_accessible (widget); 

   if (strcmp (pspec->name, "property-of-interest") == 0) 

   { 

      /* Handle the property change. */ 

   } 

   else 

   { 

      parent_class->notify_gtk (obj, pspec); 

   } 

} 

</programlisting>

</example>

</listitem>

<listitem>

<para>parent->finalize</para>

<para>

If it is necessary to free any data when a <type>GObject</type> instance is destroyed, then a <function>finalize()</function> function is needed to free the memory.  For example:

</para>

<example>

<title>自定义 <function>finalize()</function> 函数</title>

<programlisting>

void 

myatkimp_mytype_finalize (GObject *object) 

{ 

   MyAtkimpMyType *my_type = MYATKIMP_MYTYPE (object); 

   g_object_unref (my_type->cached_value); 

   G_OBJECT_CLASS (parent_class)->finalize (object); 

} 

</programlisting>

</example>

</listitem>

</orderedlist>

</listitem>

</orderedlist>

</section>

</section>

</section>

<section id="gad-custom">

<title>让自定义组件获得辅助功能</title>

<para>

Adding ATK support to your custom widget will assure its cooperation with the accessibility infrastructure. These are the general steps that are required:

</para>

<itemizedlist>

<listitem>

<para>

assess a custom widget according to the applicable <link linkend="gad-ui-guidelines">User Interface Guidelines</link>;

</para>

</listitem>

<listitem>

<para>

determine which <ulink url="https://developer.gnome.org/atk/stable/interfaces.html">ATK interfaces</ulink> a custom widget should implement, according to the widget's feature set and function;

</para>

</listitem>

<listitem>

<para>

assess which <ulink url="https://developer.gnome.org/atk/stable/interfaces.html">ATK interfaces</ulink> can be inherited from the parent widget class;

</para>

</listitem>

<listitem>

<para>部件类的 ATK 接口可以两种方式实现：</para>

<itemizedlist>

<listitem>

<para>直接由自定义部件，或者</para>

</listitem>

<listitem>

<para>

in an <ulink url="http://library.gnome.org/devel/atk/stable/AtkObject.html"><type>AtkObject</type></ulink> subtype created by a new <ulink url="http://library.gnome.org/devel/atk/stable/AtkObjectFactory.html"><type>AtkObjectFactory</type></ulink> subclass

</para>

</listitem>

</itemizedlist>

<para>如果使用第二种方法，则在运行时必须使用 <type>AtkObjectFactoryRegistry</type> 来注册合适的 factory 类型。</para>

</listitem>

</itemizedlist>

<para><ulink url="ftp://ftp.gnome.org/pub/GNOME/sources/gail/">GAIL source code</ulink> 提供了一个优秀的教程讲解高级 ATK 用法。</para>

</section>

<section id="gad-ui-guidelines">

<title>获取辅助功能支持的用户界面指南</title>

<para>

When designing your application's GUI, there are a number of simple guidelines you should follow to ensure that it can be used by as wide an audience as possible, whether in conjunction with assistive technologies or not. Don't be fooled into thinking that this is just a case of "making your GUI usable by people with disabilities", though, and that you shouldn't bother if you know a disabled person is never going to use your application. Following these guidelines will improve the overall usability of your application for everyone who uses it - including you!

</para>

<section>

<title>综述</title>

<para>

We all get frustrated if we can't find a feature in an application, or make a mistake from which it takes a couple of minutes to recover, if it's possible to recover at all.  If you have some sort of disability, the chances are the effort and time penalties involved will be several times worse. Following a few basic guidelines can help prevent these sorts of situations for all users.

</para>

<itemizedlist>

<listitem>

<para>

Provide Undo for every action that changes the user's data or the application's settings. If possible, provide more than one level of undo and redo, and a history list to allow preview of what actions will be undone.

</para>

</listitem>

<listitem>

<para>

Provide commands to restore default settings. If a particular setting could make the application completely unusable for an individual, e.g. by making the fonts very small, it would be useful to provide an option to restore the default settings outside the application itself. This could be done using a command line switch, for example.

</para>

</listitem>

<listitem>

<para>

Help prevent users from doing the wrong thing. This is particularly important for actions that could be done by accident (e.g. mouse actions) or that cannot easily be undone (e.g. overwriting a file). Consider using confirmation dialogs or forcing the user to go into a particular mode to perform potentially destructive actions.

</para>

</listitem>

<listitem>

<para>

Minimize users' memory load. For example, let the user view multiple documents at the same time, and ensure online help or other instructions can remain visible while they carry out the procedure being described. Allow them to copy any information that is displayed, and paste it anywhere that data can be entered.

</para>

</listitem>

<listitem>

<para>

Don't make users insert disks. Depending on a user's particular disability, they may find it difficult to physically insert or change a disk, or they may find it hard to identify the correct disk in the first place. If your application is installed from CD-ROM, provide an option to copy all the files that will be required onto the user's hard drive.

</para>

</listitem>

<listitem>

<para>

Don't place frequently used functions deep in a menu structure. Whether you're using a mouse, keyboard or some other input device, deeply-nested menu items are best avoided. As well as the burden of remembering where to find them, they are always more difficult and time-consuming to access.

</para>

</listitem>

<listitem>

<para>

Don't lead users through unnecessary steps. For example, wizards are useful for users who have trouble handling large numbers of options at one time, but other users may need to minimize the amount of time or keystrokes they use.  Such users benefit from being able to skip unnecessary steps or go directly to the one they need. Consider providing a <guibutton>Finish</guibutton> button in wizards that skips right to the end and assumes default responses for the intermediate steps. If the process has many steps, consider asking the user at the start if they want to run through all the steps, or just the most commonly-used ones.

</para>

</listitem>

</itemizedlist>

</section>

<section>

<title>键盘导航</title>

<para>

A well-designed keyboard user interface plays a key role when you are designing accessible software. Blind users can navigate software more effectively using the keyboard, because using the mouse depends on visual feedback of the mouse pointer location. Also, mobility impairments can prevent a user from successfully navigating using the mouse, because of the fine motor control skills required.

</para>

<para>

It is therefore important to make all mouse actions available from the keyboard, and include keyboard access to all toolbars, menus, links and buttons. Every function your application provides should be available using the keyboard alone. Hide your mouse while you're testing your application if you have to!

</para>

<para>

Most functionality should be easy to make accessible by using keyboard mnemonics and accelerators, and the toolkit's built-in navigation features. However, operations that rely on drag-and-drop, for example, may require more thought.

</para>

<itemizedlist>

<listitem>

<para>

Provide efficient keyboard access to all application features. Some users may be unable to use a mouse, and many "power-users" prefer to use the keyboard anyway. Also, some specialized assistive technology input devices may simulate keyboard events rather than mouse events. Since typing is difficult or even painful for some users, it is important to provide a keyboard interface that minimizes the number of keystrokes required for any given task.

</para>

</listitem>

<listitem>

<para>

Use a logical keyboard navigation order. When navigating around a window with the <keycap>Tab</keycap> key, keyboard focus should move between controls in a predictable order.  In Western locales, this is normally left to right and top to bottom.

</para>

</listitem>

<listitem>

<para>

Ensure correct tab order for controls whose enabled state is dependent on checkbox, radio button or toggle button state. When such a button is selected, all its dependent controls should be enabled, and all the dependent controls of any other button in the group should be disabled. When the user selects a checkbox, radio button or toggle button that has dependent controls, do not automatically give focus to the first dependent control, but instead leave the focus on the button.

</para>

</listitem>

<listitem>

<para>

Don't override existing system-level accessibility features. For example, <ulink url="http://www.rehab.uiuc.edu/accessx/overview.html">AccessX</ulink> is an Xserver extension that has been supported since X11R6. The MouseKeys feature of this extension allows mouse movement and button clicks to be simulated using the keypad. Therefore you should not add features to your application that can only be accessed by pressing keys on the keypad, as users relying on the MouseKeys feature will not be able to use them.

</para>

</listitem>

<listitem>

<para>

Provide more than one method to perform keyboard tasks where possible. Some users may find some keys and key combinations easier to use than others.

</para>

</listitem>

<listitem>

<para>

Provide both keyboard and mouse access to functions where possible. Some users may only be able to use either the mouse or the keyboard, but not both.

</para>

</listitem>

<listitem>

<para>

Don't assign awkward reaches to frequently performed keyboard operations. Some people may only be able to use one hand on the keyboard, so shortcuts that can be easily used with one hand are preferable for common operations. In any case, having to frequently perform long or difficult reaches on the keyboard can increase muscle strain for all users, increasing the risk of pain or injury.

</para>

</listitem>

<listitem>

<para>

Don't require repetitive use of simultaneous keypresses. Some users are only able to press and hold one key at a time. Assistive technologies such as AccessX may allow users to press the keys sequentially rather than simultaneously, but this of course means the operation will take longer for them.

</para>

</listitem>

<listitem>

<para>

Ensure that any text that can be selected with the mouse can also be selected with the keyboard. This is a convenience for all users, but especially for those for whom fine control of the mouse is difficult.

</para>

</listitem>

<listitem>

<para>

Ensure that objects that can be resized or moved by drag and drop can also be resized or moved with the keyboard. For example, icons and windows on the desktop. Where precision sizing and placement is potentially important, e.g. shapes in a diagram, also consider providing a dialog into which you can type co-ordinates, or a means of snapping objects to a user-definable grid.

</para>

</listitem>

<listitem>

<para>

Don't use general navigation functions to trigger operations. For example, do not use basic <keycap>Tab</keycap> keyboard navigation in a dialog to activate any actions associated with a control.

</para>

</listitem>

<listitem>

<para>

Show keyboard-invoked menus, windows and tooltips near the object they relate to. In GNOME 2.0, users can call up popup menus with <keycombo><keycap>Shift</keycap><keycap>F10</keycap></keycombo>, and tooltips with <keycombo><keycap>Shift</keycap><keycap>F1</keycap></keycombo>. Do not completely hide or obscure the object to which the menu or tooltip refers, however.

</para>

</listitem>

</itemizedlist>

</section>

<section>

<title>鼠标交互</title>

<para>记住，不是所有人都能灵巧使用鼠标，某些用户可能很难看见或跟随鼠标指针。</para>

<itemizedlist>

<listitem>

<para>

Don't depend on input from mouse button 2 or button 3. As well as being physically more difficult to click, some pointing devices and many assistive technology devices only support button 1. Some assistive technologies may not emulate the mouse at all, but generate keyboard events instead.

</para>

</listitem>

<listitem>

<para>

Allow all mouse operations to be cancelled. Pressing the <keycap>Esc</keycap> key should cancel any mouse operation in progress, such as dragging and dropping a file in a file manager, or drawing a shape in a drawing program.

</para>

</listitem>

<listitem>

<para>

Provide visual feedback throughout a drag and drop operation. As the mouse passes over valid targets, highlight them and change the mouse pointer. Use the "no drop" mouse pointer when passing over invalid drop targets. See <link linkend="gad-mouse-examples">Mouse Interaction Examples</link>.