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Sugar activities are usually written in Python using the [http://api.sugarlabs.org/ Python Activity API]. This page documents the underlying mechanism that all activities need to conform to. Activities can be written in any language, as long as it can connect to D-Bus and provide an X11 interface. The discussion below tries to be language-agnostic.

Sugar activities are usually written in Python using the [http://api.sugarlabs.org/ Python Activity API]. This page documents the underlying mechanism that all activities need to conform to. Activities can be written in any language, as long as it can connect to D-Bus and provide an X11 interface. The discussion below tries to be language-agnostic.

This can be used to, e.g., open a URL (create a URL object in the journal then call this) or to view source code (store the source code as text file, then call ShowObject() on it).

This can be used to, e.g., open a URL (create a URL object in the journal then call this) or to view source code (store the source code as text file, then call ShowObject() on it).

Note: since Sugar 0.84, you also can give the full path to an existing file instead of an object id. If the user resumes that file, it will be copied to the Journal first and the opened using the chosen activity. <i>This seems to be of limited usefulness and is documented here just for completeness</i>  

Note: since Sugar 0.84, you also can give the full path to an existing file instead of an object id. If the user resumes that file, it will be copied to the Journal first and then opened using the chosen activity. <i>This seems to be of limited usefulness and is documented here just for completeness</i>  

<s>To focus on multiple objects: <code>org.laptop.Journal.FocusSearch(query)</code></s> ''Removed in Sugar 0.83''

<s>To focus on multiple objects: <code>org.laptop.Journal.FocusSearch(query)</code></s> ''Removed in Sugar 0.83''

==Mount Points==

==Mount Points==

<strike>Devices are represented as mount points in the datastore. If no mountpoint is explicitly specified, the main datastore (Journal) is used.

<strike>

Devices are represented as mount points in the datastore. If no mountpoint is explicitly specified, the main datastore (Journal) is used.

   mounts = datastore.mounts()

   mounts = datastore.mounts()

Mount points can be specified when creating an object (using a 'mountpoint' key and id value in the properties), and when querying the datastore (by adding a 'mountpoints' query option).

Mount points can be specified when creating an object (using a 'mountpoint' key and id value in the properties), and when querying the datastore (by adding a 'mountpoints' query option).

Large files to be stored on an external device should be placed at the uri of the mount point</strike> (see [[#External Media|external media]]).

Large files to be stored on an external device should be placed at the uri of the mount point (see [[#External Media|external media]]).

'''Note:''' ''This only works as described in Sugar up to 0.82. The functions do exist in later Sugar versions, but do not return useful data.''

'''Note:''' ''This only works as described in Sugar up to 0.82. The functions do exist in later Sugar versions, but do not return useful data. Use the [[#External Media|external media API]] instead.''

=Security=

=Security=

;$SUGAR_ACTIVITY_ROOT/data/: This directory is used similar to a traditional home directory, for persistent activity data such as configuration files. Make sure files in there are group readable and writable (see [[#Users and Groups|users and groups]]). The directory itself is group-writable. Files stored here will survive reboots and OS upgrades.

;$SUGAR_ACTIVITY_ROOT/data/: This directory is used similar to a traditional home directory, for persistent activity data such as configuration files. Make sure files in there are group readable and writable (see [[#Users and Groups|users and groups]]). The directory itself is group-writable. Files stored here will survive reboots and OS upgrades.

;$SUGAR_ACTIVITY_ROOT/tmp/: This directory is used similar to a /tmp directory, being backed by RAM. It may be as small as 1 MB. This directory is deleted when the activity exits (specifically,  as soon as all children of the activity's first process die). This directory is ''only'' accessible to the activity and its children; not even to Sugar.

;$SUGAR_ACTIVITY_ROOT/tmp/: This directory is used similar to a /tmp directory, being backed by RAM if [[olpc:Rainbow|Rainbow]] is present. It may be as small as 1 MB. With [[olpc:Rainbow|Rainbow]], this directory is deleted when the activity exits (specifically,  as soon as all children of the activity's first process die). This directory is ''only'' accessible to the activity and its children; not even to Sugar.

;$SUGAR_ACTIVITY_ROOT/instance/: This directory is used similar to a /var/tmp directory, being backed by flash rather than by RAM. It is unique per instance. It is used for transfer to and from the datastore (see [[#Keeping and Resuming|keeping and resuming]]). This directory is deleted when the activity exits (specifically,  as soon as all children of the activity's first process die)

;$SUGAR_ACTIVITY_ROOT/instance/: This directory is used similar to a /var/tmp directory, being backed by flash rather than by RAM. It is unique per instance. It is used for transfer to and from the datastore (see [[#Keeping and Resuming|keeping and resuming]]). With [[olpc:Rainbow|Rainbow]], this directory is deleted when the activity exits (specifically,  as soon as all children of the activity's first process die).

As of version 8.2, all the activity root directories are created in /home/olpc/isolation and can be examined there with the Terminal activity. However, activities MUST use the $SUGAR_ACTIVITY_ROOT variable because the isolation directory layout is expected to change.

As of version 8.2, all the activity root directories are created in /home/olpc/isolation and can be examined there with the Terminal activity. However, activities MUST use the $SUGAR_ACTIVITY_ROOT variable because the isolation directory layout is expected to change.

=== External Media ===

=== External Media ===

External media (USB drives, SD cards) are auto-mounted by the Journal and appear in /media/*. No access restrictions are applied currently (up to release 8.2). If activities use these external media directly (rather than through the Journal, see [[#Mount Points|mount points]]), they need to take care of ensuring data integrity since the user may (and will) remove the medium at any time.

External media (USB drives, SD cards) are auto-mounted by the Journal. No access restrictions are applied currently. If activities use these external volumes directly, they need to take care of ensuring data integrity since the user may (and will) remove the medium at any time.

 

Depending on the Linux distro version, the volumes appear as /mnt/*, /media/*, /run/media/$USER/*, or in other places. Sugar up to version 0.82 provided an API to access their [[#Mount Points|mount points]]. Nowadays you should use general Linux API to find the volumes. The recommended way is using the [http://developer.gnome.org/gio/stable/GVolumeMonitor.html GNOME Volume Monitor] with a fallback to [http://www.freedesktop.org/wiki/Software/hal HAL] (there is an example in the [http://git.sugarlabs.org/backup/mainline/blobs/master/backup.py#line671 Backup activity]).

== Signing ==

== Signing ==

''Note: The Presence Service has been deprecated. Activities need to talk to [[Telepathy]] directly instead. See [[#Collaboration|below]] for details''

''Note: The Presence Service has been deprecated. Activities need to talk to [[Telepathy]] directly instead. See [[#Collaboration|below]] for details''

==General==

==General==

  BuddyJoined (o: buddy)

  BuddyJoined (o: buddy)

  BuddyLeft (o: buddy)

  BuddyLeft (o: buddy)

==Tubes==

==Tubes==