Development Team/Almanac/Activity Bundles

Introduction

Every activity in the Sugar environment is packaged into a self-contained "bundle". The bundle contains all the resources and executable code (other than system-provided base libraries) which the activity needs to execute. Any resources or executable code that is not provided by the base system must be packaged within the bundle.

Rationale

Activities are meant to be shared between children. If a child doesn't have the activity, it is automatically transfered to the child when he or she joins the shared activity. Packaging activities in self-contained bundles allows easy sharing, installation, removal, and backup.

Location

Activities are installed and removed automatically by Sugar, in response to user actions. Sugar places activities in directory of its choice. Activities should not rely on being installed in a specific location, and should use relative paths where paths are necessary (i.e., for shared library linkage, activity resources such as images, sounds, etc). They should also not rely on the bundle's base directory name remaining the same. Sugar may rename the activity bundle base directory at any time to prevent bundle conflicts.

Sugar will automatically generate and remove the .service files necessary to launch the activity through D-Bus service activation when the activity is installed or removed.

Activities should also NEVER store local state or preferences in the activity bundle itself. These should always be stored in an activity-specific directory in the user's sugar profile, available through the SUGAR_PROFILE environment variable.

Bundle Structure

The activity bundle is a directory, with a name ending in ".activity". Each activity bundle must, in its root directory, contain a file named "activity.info", and following a special format. For example:

Web.activity/
    activity.info
    localized/
    web-activity.svg
    images/
    sounds/
    bin/

(the images, sounds, and bin subdirectories are not required, but are shown as examples of how an activity may wish to organize its resources)

The 'localized' directory contains localizations of the activity bundle's name. It must be present.

.info File Format

.info files follow a key/value pair format, similar to the Desktop Entry standard, but not conforming to it. An example is shown here:

[Activity]
name = Web
activity_version = 1
host_version = 1
service = com.redhat.Sugar.BrowserActivity
icon = activity-web
exec = sugar-activity-factory com.redhat.Sugar.BrowserActivity BrowserActivity.BrowserActivity
show_launcher = yes

A more detailed explanation of each line follows:

[Activity]

The activity.info file must begin with [Activity], and only that, on the first line of the file

name = Web

This is the name is displayed in Sugar referring to the activity. A 'name' key without a bracketed language code is the "en_US" localized name of the activity. The activity.info file must have this key.

activity_version = 1

Each activity.info file must have a "activity_version" key. The version is a single positive integer, and may only contain the characters 1 through 9. Larger versions are considered "newer".

host_version = 1

Each activity.info file must have a "host_version" key. The version is a single positive integer, and may only contain the characters 1 through 9. This specifies the version of the Sugar environment which the activity is compatible with. (fixme: need to specify sugar versions somewhere. Obviously we start with 1.)

service = com.redhat.Sugar.BrowserActivity

This is the activity's dbus service name. It is required. It is also used as the activity's default service type when the activity is shared on the network. To determine this type, the distince parts (separated by the '.' character) are reversed, any '.' is replaced by a '_' character, and the type is prefixed by a '_' character. So in this example, the default service type would be "_BrowserActivity_Sugar_redhat_com".

icon = activity-web

This key is optional. It points to the activity's icon. The icon is first searched for in the activity bundle's root directory, and if not found, is looked up in the current GTK icon theme. It cannot contain a path.

exec = sugar-activity-factory com.redhat.Sugar.BrowserActivity BrowserActivity.BrowserActivity

The exec key are used when Sugar installs the activity. It specifies the executable which Sugar runs to start the activity's factory service. A factory service spawns instances of the actual activity. A factory service for Python-based activities is provided with Sugar.

show_launcher = yes

This key is optional. If not present, or if present with a value of "yes", the activity is shown with its icon in the Sugar panel launcher and a valid 'icon' key/value pair is required. If specified with a value of "no", the activity is not shown in the Sugar panel launcher, and the 'icon' key is not required.