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== Introduction ==

== Introduction ==

The purpose of this Guide is describing how to use package activities that use Sugar Services.

The purpose of this Guide is to describe how to package activities that use Sugar Services.

== Activity dependencies ==

== Activity dependencies ==

Every activity which uses Sugar Services will contain additional options in activity.info file:

Every activity that uses Sugar Services will contain additional options in an activity.info file:

* ''requires'' option, comma separated list of dependencies that should exist

* ''requires'' option, a comma-separated list of dependencies that should exist,

* ''suggests'' option, comma separated list of dependencies that could not exist

* ''suggests'' option, a comma-separated list of dependencies that could not exist.

Each dependency could be:

Each dependency could be a,

* service name, the full 0install link will be http://services.sugarlabs.org/<dependency-name>

* service name, the full 0install link will be http://services.sugarlabs.org/<dependency-name>,

* sub service slashed name, the full 0install link will be http://services.sugarlabs.org/<dependency-name>.xml

* sub service slashed name, the full 0install link will be http://services.sugarlabs.org/<dependency-name>.xml

* full 0install link

* full 0install link.

In any case resulted 0install link will contain proper information about dependency - home page, link to sources, licence etc.

In any case, the resulting 0install link will contain the appropriate information about dependency - home page, link to sources, licence, etc.

Activity itself doesn't contain any 0sugar related code, 0sugar will export proper environment variables to activity process e.g. PYTHONPATH or LD_LIBRARY_PATH thus dependencies could packaged and activity will not notice any differences between 0install dependencies and installed from packages. Exception is libsugarize service which exports LD_PRELOAD environment variable.

The activity itself doesn't contain any 0sugar-related code. 0sugar will export the appropriate environment variables to the activity process, e.g., PYTHONPATH or LD_LIBRARY_PATH. Thus, dependencies could be packaged and the activity will not notice any differences between 0install dependencies and those installed from packages. An exception is the libsugarize service, which exports the LD_PRELOAD environment variable.

== Cache directory ==

== Cache directory ==

Every activity which uses Sugar Services will contain .0sugar subdirectory in activity root:

Every activity that uses Sugar Services will contain a .0sugar subdirectory in its activity root

* to keep all dependencies implementations (to not download them on demand)<br>could be any content including binaries

* to keep all necessary dependency implementations (so as not to download them on demand).<br>This could be any content, including binaries.

* 0sugar launching code, since 0sugar is not part of Sugar Platform<br>pure python code

* 0sugar launching code, since 0sugar is not part of Sugar Platform.<br>This is pure python code.

* .0sugar/launch script that starts 0sugar launching code<br>''exec'' option from activity.info invokes this script

* .0sugar/launch script, which starts 0sugar launching code<br>The ''exec'' option from activity.info invokes this script.

  exec $(dirname $0)/<path-to-0sugar>/0sugar-selector "$@"

  exec $(dirname $0)/<path-to-0sugar>/0sugar-selector "$@"

If all dependencies(including 0sugar) are packaged then this directory could be just removed.

If all dependencies (including 0sugar) are packaged, then this directory could be just removed.