デスクトップエントリ

デスクトップエントリは X Window System で動作するプログラムの挙動を指定する freedesktop.org の仕様です。デスクトップエントリは設定ファイルとしてアプリケーションの起動方法やメニューとアイコンの表示方法を定義します。最も一般的なデスクトップエントリは .desktop と .directory ファイルです。この記事では有用な標準仕様のデスクトップエントリを作成する方法を簡単に説明します。主にパッケージ作成者やメンテナを対象にしていますが、ソフトウェアの開発者なども読む価値があると思われます。

デスクトップエントリには大きくわけて3つのタイプがあります:

アプリケーション: アプリケーションのショートカット
リンク: ウェブリンクのショートカット。
ディレクトリ: メニューエントリのメタデータのコンテナ。

以下のセクションではこれらのエントリを作成したり修正する方法をざっと説明しています。

アプリケーションエントリ

アプリケーションのデスクトップエントリ、または .desktop ファイルは、基本的にメタ情報の集合でありアプリケーションのショートカットです。これらのファイルは基本的に、システム全体でインストールしたアプリケーションなら /usr/share/applications または /usr/local/share/applications に、ユーザー個別にインストールしたアプリケーションなら ~/.local/share/applications に入っています。ユーザーのエントリはシステムのエントリよりも優先されます。

サンプルファイル

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

キーの定義

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.

非推奨

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.

アイコン

一般的な画像フォーマット

以下はアイコンとしてよく使われている画像フォーマットの簡単な概要です。

freedesktop.org の仕様で指定されているアイコンとしてサポートされる画像フォーマット
拡張子	フルネームまたは説明	グラフィック形式	コンテナフォーマット	サポート
.png	Portable Network Graphics	ラスタ	no	yes
.svg(z)	Scalable Vector Graphics	ベクタ	no	yes (optional)
.xpm	X PixMap	ラスタ	no	yes (deprecated)
.gif	Graphics Interchange Format	ラスタ	no	no
.ico	MS Windows Icon Format	ラスタ	yes	no
.icns	Apple Icon Image	ラスタ	yes	no

アイコンの変換

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.)

アイコンの取得

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.

ツール

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).

使用方法

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.

参照