Desktop entries (简体中文)

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翻译状态： 本文是英文页面 Desktop_entries 的翻译，最后翻译时间：2015-11-15，点击这里可以查看翻译后英文页面的改动。

桌面配置项（Desktop entries）是 freedesktop.org（自由桌面社区） 制订的一个用于规范 Xorg 环境中程序运行行为的标准。它是一个配置文件，描述了某个应用程序如何被启动以及怎样在菜单中以图标形式出现。大部分桌面配置项是 .desktop 和 .directory 文件。本文将概述如何创建一个合规可用的桌面配置项，主要面向软件包发布者和维护者，但对软件开发者及其他人也会是有用的。

桌面配置项大致分为三类：

应用程序 

指向某个应用程序的快捷方式

链接 

指向某个网址的链接

目录 

某个菜单项元数据的容器

下列章节概述如何创建它们并使其生效。

应用程序配置项

Desktop entries for applications, or .desktop files, are generally a combination of meta information resources and a shortcut of an application. These files usually reside in /usr/share/applications or /usr/local/share/applications for applications installed system-wide, or ~/.local/share/applications for user-specific applications. User entries take precedence over system entries.

范例文件

Following is an example of its structure with additional comments. The example is only meant to give a quick impression, and does not show how to utilize all possible entry keys. The complete list of keys can be found in the freedesktop.org specification.

[Desktop Entry]
Type=Application                          # Indicates the type as listed above
Version=1.0                               # The version of the desktop entry specification to which this file complies
Name=jMemorize                            # The name of the application
Comment=Flash card based learning tool    # A comment which can/will be used as a tooltip
Exec=jmemorize                            # The executable of the application.
Icon=jmemorize                            # The name of the icon that will be used to display this entry
Terminal=false                            # Describes whether this application needs to be run in a terminal or not
Categories=Education;Languages;Java;      # Describes the categories in which this entry should be shown

关键字定义

All Desktop recognized desktop entries can be found on the freedesktop.org site. For example, the Type key defines three types of desktop entries: Application (type 1), Link (type 2) and Directory (type 3).

• Version key does not stand for the version of the application, but for the version of the desktop entry specification to which this file complies.

• Name, GenericName and Comment often contain redundant values in the form of combinations of them, like:

Name=Pidgin Internet Messenger
GenericName=Internet Messenger

or

Name=NoteCase notes manager
Comment=Notes Manager

This should be avoided, as it will only be confusing to users. The Name key should only contain the name, or maybe an abbreviation/acronym if available.

• GenericName should state what you would generally call an application that does what this specific application offers (i.e. Firefox is a "Web Browser").
• Comment is intended to contain any usefull additional information.

过时的内容

There are quite some keys that have become deprecated over time as the standard has matured. The best/simplest way is to use the tool desktop-file-validate which is part of the package desktop-file-utils. To validate, run

$ desktop-file-validate <your desktop file>

This will give you very verbose and useful warnings and error messages.

图标

通用图像格式

Here is a short overview of image formats commonly used for icons.

Support for image formats for icons as specified by the freedesktop.org standard.

Extension	Full Name and/or Description	Graphics Type	Container Format	Supported
.png	Portable Network Graphics	Raster	no	yes
.svg(z)	Scalable Vector Graphics	Vector	no	yes (optional)
.xpm	X PixMap	Raster	no	yes (deprecated)
.gif	Graphics Interchange Format	Raster	no	no
.ico	MS Windows Icon Format	Raster	yes	no
.icns	Apple Icon Image	Raster	yes	no

图标格式转换

If you stumble across an icon which is in a format that is not supported by the freedesktop.org standard (like gif or ico), you can convert (which is part of the imagemagick package) it to a supported/recommended format, e.g.:

$ convert <icon name>.gif <icon name>.png

If you convert from a container format like ico, you will get all images that were encapsulated in the ico file in the form <icon name>-<number>.png. If you want to know the size of the image, or the number of images in a container file like ico you can use identify (also part of the imagemagick package)

$ identify /usr/share/vlc/vlc48x48.ico
/usr/share/vlc/vlc48x48.ico[0] ICO 32x32 32x32+0+0 8-bit DirectClass 84.3kb
/usr/share/vlc/vlc48x48.ico[1] ICO 16x16 16x16+0+0 8-bit DirectClass 84.3kb
/usr/share/vlc/vlc48x48.ico[2] ICO 128x128 128x128+0+0 8-bit DirectClass 84.3kb
/usr/share/vlc/vlc48x48.ico[3] ICO 48x48 48x48+0+0 8-bit DirectClass 84.3kb
/usr/share/vlc/vlc48x48.ico[4] ICO 32x32 32x32+0+0 8-bit DirectClass 84.3kb
/usr/share/vlc/vlc48x48.ico[5] ICO 16x16 16x16+0+0 8-bit DirectClass 84.3kb

As you can see, the example ico file, although its name might suggest a single image of size 48x48, contains no less than 6 different sizes, of which one is even greater than 48x48, namely 128x128. And to give a bit of motivation on this subject, at the point of writing this section (2008-10-27), the 128x128 size was missing in the vlc package (0.9.4-2). So the next step would be to look at the vlc PKGBUILD and check whether this icon format was not in the source package to begin with (in that case we would inform the vlc developers), or whether this icon was somehow omitted from the Arch-specific package (in that case we can file a bug report at the Arch Linux bug tracker). (Update: this bug has now been fixed, so as you can see, your work will not be in vain.)

Obtaining icons

Although packages that already ship with a .desktop-file most certainly contain an icon or a set of icons, there is sometimes the case when a developer has not created a .desktop-file, but may ship icons, nonetheless. So a good start is to look for icons in the source package. You can i.e. first filter for the extension with find and then use grep to filter further for certain buzzwords like the package name, "icon", "logo", etc, if there are quite a lot of images in the source package.

$ find /path/to/source/package -regex ".*\.\(svg\|png\|xpm\|gif\|ico\)$"

If the developers of an application do not include icons in their source packages, the next step would be to search on their web sites. Some projects, like i.e. tvbrowser have an artwork/logo page where additional icons may be found. If a project is multi-platform, there may be the case that even if the linux/unix package does not come with an icon, the Windows package might provide one. If the project uses a Version control system like CVS/SVN/etc. and you have some experience with it, you also might consider browsing it for icons. If everything fails, the project might simple have no icon/logo yet.

工具

gendesk

gendesk started as an Arch Linux-specific tool for generating .desktop files by fetching the needed information directly from PKGBUILD files. Now it is a general tool that takes command-line arguments.

Icons can be automatically downloaded from openiconlibrary, if available. (The source for icons can easily be changed in the future).

用法

• Add gendesk to makedepends

• Start the prepare() function with:

gendesk --pkgname "$pkgname" --pkgdesc "$pkgdesc"

• Alternatively, if an icon is already provided ($pkgname.png, for instance). The -n flag is for not downloading an icon or using the default icon. Example:

gendesk -n --pkgname "$pkgname" --pkgdesc "$pkgdesc"

• $srcdir/$pkgname.desktop will be created and can be installed in the package() function with:

install -Dm644 "$pkgname.desktop" "$pkgdir/usr/share/applications/$pkgname.desktop"

• The icon can be installed with:

install -Dm644 "$pkgname.png" "$pkgdir/usr/share/pixmaps/$pkgname.png"

• Use --name='Program Name' for choosing a name for the menu entry.

• Use --exec='/opt/some_app/elf --with-ponies' for setting the exec field.

• See the gendesk project for more information.

lsdsk

The lsdsk^AUR bash script searching for content in "Categories" or "Exec", if "Categories" doesn't exist then it uses content of "Name". It's main purpose to get a quick overview in console of the available programs with their command lines and categories in *.desktop. It shows coloured existing base path defined in "DskPath" array.

Examples

# lsdsk
# lsdsk game
# lsdsk gtk

fbrokendesktop

The fbrokendesktop^AUR bash script using command "which" to detect broken Exec that points to not existing path. Without any parameters it uses preset folders in "DskPath" array. It shows only broken *.desktop with full path and filename that is missing.

Examples

# fbrokendesktop
# fbrokendesktop /usr
# fbrokendesktop /usr/share/apps/kdm/sessions/icewm.desktop

提示与技巧

隐藏桌面配置项

Tip: Desktop entries can be hidden by creating a symbolic link to /dev/null. For example:

$ ln -s /dev/null ~/.local/share/applications/foo.desktop

Firstly, copy the desktop entry file in question to ~/.local/share/applications to avoid your changes being overwritten.

Then, to hide the entry in all environments, open the desktop entry file in a text editor and add the following line: NoDisplay=true.

To hide the entry in a specific desktop, add the following line to the desktop entry file: NotShowIn=desktop-name

where desktop-name can be option such as GNOME, Xfce, KDE etc. A desktop entry can be hidden in more than desktop at once - simply separate the desktop names with a semi-colon.

自动启动

If you use an XDG-compliant desktop environment, such as GNOME or KDE, the desktop environment will automatically start *.desktop files found in the following directories:

• System-wide: $XDG_CONFIG_DIRS/autostart/ (/etc/xdg/autostart/ by default)

• GNOME also starts files found in /usr/share/gnome/autostart/

• User-specific: $XDG_CONFIG_HOME/autostart/ (~/.config/autostart/ by default)

Users can override system-wide *.desktop files by copying them into the user-specific ~/.config/autostart/ folder.

For an explanation of the desktop file standard refer to Desktop Entry Specification. For a more specific description of directories used, Desktop Application Autostart Specification.

Note: This method is supported only by XDG-compliant desktop environments. Tools like dapper^AUR, dex, or fbautostart^AUR can be used to offer XDG autostart in unsupported desktop environments as long as some other autostart mechanism exists. Use the existing mechanism to start the xdg compliant autostart tool.

参阅

• DeveloperWiki:Removal of desktop files
• desktop wikipedia article
• recognized desktop entry keys
• freedesktop.org desktop entry specification
• freedesktop.org icon theme specification
• freedesktop.org menu specification
• freedesktop.org basedir specification
• information for developers