Sugar Architecture

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The Sugar Interface acts as the primary user interface for most children using an OLPC laptop. It runs as a graphical shell on top of a trimmed down implementation of Redhat's Fedora implementation of a Linux operating system. Python has been selected as the primary development language for sugar.
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This page describes the components in which Sugar is divided and gives pointers to the relevant parts of the source code. The intention is to give a starting point to the people that want to start hacking on Sugar.
 +
 
 +
==Dependencies==
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Sugar is mainly coded in python making extensive use of PyGTK/gtk2 (including Pango) and python-dbus/dbus-X11. Other dependencies are
 +
 
 +
* avahi-daemon
 +
* matchbox-window-manager
 +
* network-manager
 +
* python-avahi
 +
* python-cairo
 +
* python-central
 +
* python-gnome2-desktop
 +
* python-hippocanvas
 +
* python-json
 +
* python-numpy
 +
* telepathy-stream-engine
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* gstreamer
 +
* rsvg
 +
* xapian
 +
* vte
 +
 
 +
 
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== Components ==
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In order to understand how these components map to the user-visible elements, familiarity with [[OLPC Human Interface Guidelines]] is required.
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=== Shell ===
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Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell
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The Sugar Shell is the UI component that provides the following services to the user:
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 +
* starting, stopping and joining activities,
 +
* managing devices (network connection, battery, etc),
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* managing the clipboard,
 +
* managing groups of buddies.
 +
 
 +
Basically, all that the user does outside activities is done in the shell.
 +
 
 +
The shell can be divided in two major components, the Frame and the Home view.
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 +
Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell/view/frame
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The frame is implemented as four top level windows that cover the border of the screen when visible. Every side of the frame contains icons organized in trays (gtk.Toolbar). See [[OLPC Human Interface Guidelines/The Laptop Experience/The Frame]].
 +
 
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Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell/view/home
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The home view is a top-level window with the DESKTOP hint. The three zoom levels are implemented as hippo.Canvas embedded in that window. See [[OLPC Human Interface Guidelines/The Laptop Experience/Zoom Metaphor]].
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=== Activities ===
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What are called applications or programs in other environments, are activities in Sugar, see [[OLPC Human Interface Guidelines/Activities]].
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Activity authors need to understand how the activity concept is different from traditional applications and how its software can make better use of the Sugar platform.
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Activities can happen in isolation or in collaboration with other users.
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What is a correct activity from the implementation point of view:
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* a top level X window with some predefined properties, see [[Low-level Activity API#X Properties]],
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* behaves properly when running inside [[Rainbow]], see [[Low-level_Activity_API#Security]],
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* saves its state to the Datastore when needed, see [[Low-level_Activity_API#Datastore]],
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* can resume that state so the user is confronted with the same state as when the activity was closed,
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* provides a D-Bus service that the shell can use, see [[Low-level_Activity_API#D-Bus_Methods]],
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* can collaborate, that means that its state is shared between several instances running each on an XO, see [[Low-level_Activity_API#Presence]].
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Activities can choose between using the low level APIs presented above, or the higher-level [[Sugar_Architecture#Activity_API]] presented below.
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=== Shell service ===
 +
 
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Code: http://dev.laptop.org/git?p=sugar;a=tree;f=services/shell
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 +
The shell service provides the following subservices to the Shell:
 +
 
 +
* clipboard: store clippings, this is basically the backend of the clipboard tray in the left frame,
 +
* activity registry: manages a registry of the installed activities,
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* object type registry: maintains a mapping of mime type to "umbrella" types, these are high level object types like Image, Audio, Video, etc that are used to give the user an uniform view of objects in the clipboard and in the journal.
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These services are offered as D-Bus interfaces.
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=== Journal ===
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Code: http://dev.laptop.org/git?p=journal-activity;a=tree
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The Journal keeps track of what the user has done with the laptop. Every activity should keep records in the journal so the user can see what has been done in the past and probably resume some past activity.
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All this data produced by the activities is kept by the Datastore service, and the journal provides to the user different ways of querying and browsing past works.
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=== Datastore service ===
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Code: http://dev.laptop.org/git?p=projects/datastore;a=tree
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Provides activities with a way to store data and metadata and the journal with means for querying, including full text search.
 +
 
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=== Presence service ===
 +
 
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Code: http://dev.laptop.org/git?p=projects/presence-service;a=tree
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See [[Presence Service]].
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=== Activity API ===
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Code: http://dev.laptop.org/git?p=sugar;a=tree;f=lib
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This API aims to make the development of new activities as simple and straightforward as possible.
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Currently it is only available to activities implemented in python, but the plan is to gradually rewrite it in C and make available bindings for different languages.
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{{pending|TODO: link to the activity API pydocs}}
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Contains the following modules:
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* activity: contains a base Activity class for activities to subclass, see [[Activity_tutorial]],
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* graphics: provides gtk-based widgets that integrate better with Sugar,
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* presence: wrapper around the [[Sugar_Architecture#Presence_service]],
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* datastore: wrapper around the [[Sugar_Architecture#Datastore_service]],
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* bundle: provides functionality for manipulating [[Bundle]]s,
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* clipboard: wrapper around the clipboard service in [[Sugar_Architecture#Shell_service]], instead of accessing the clipboard through this module, activities should make use of the X selection mechanism, see http://en.wikipedia.org/wiki/X_Window_selection. Activities using PyGTK can use [http://www.pygtk.org/pygtk2reference/class-gtkclipboard.html gtk.Clipboard], see also [http://www.pygtk.org/pygtk2tutorial/ch-NewInPyGTK2.2.html#sec-Clipboards Clipboards].
== Specifications ==
== Specifications ==
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== [[Sugar Architecture/API | API]] ==
== [[Sugar Architecture/API | API]] ==
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* [[API | Sugar APIs]]
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* [[Low-level Activity API]]
* [[Presence Service DBus API]]
* [[Presence Service DBus API]]
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* [[Activity DBus API]]
 
* [[HippoCanvas]]: Cairo drawing and UI layout widget
* [[HippoCanvas]]: Cairo drawing and UI layout widget
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* [http://dbus.freedesktop.org/doc/dbus-tutorial.html D-Bus] interprocess communications system ([http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html Python interface])
* [http://dbus.freedesktop.org/doc/dbus-tutorial.html D-Bus] interprocess communications system ([http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html Python interface])
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==Links and references==
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== Links and references ==
[http://www.python.org/doc/ Python Documentation]
[http://www.python.org/doc/ Python Documentation]
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[[Category:Sugar]]
 
[[Category:Developers]]
[[Category:Developers]]

Current revision as of 05:09, 29 May 2011

  english | 日本語中文español HowTo [ID# 256633]  +/-  

Contents

This page describes the components in which Sugar is divided and gives pointers to the relevant parts of the source code. The intention is to give a starting point to the people that want to start hacking on Sugar.

Dependencies

Sugar is mainly coded in python making extensive use of PyGTK/gtk2 (including Pango) and python-dbus/dbus-X11. Other dependencies are

  • avahi-daemon
  • matchbox-window-manager
  • network-manager
  • python-avahi
  • python-cairo
  • python-central
  • python-gnome2-desktop
  • python-hippocanvas
  • python-json
  • python-numpy
  • telepathy-stream-engine
  • gstreamer
  • rsvg
  • xapian
  • vte


Components

In order to understand how these components map to the user-visible elements, familiarity with OLPC Human Interface Guidelines is required.

Shell

Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell

The Sugar Shell is the UI component that provides the following services to the user:

  • starting, stopping and joining activities,
  • managing devices (network connection, battery, etc),
  • managing the clipboard,
  • managing groups of buddies.

Basically, all that the user does outside activities is done in the shell.

The shell can be divided in two major components, the Frame and the Home view.

Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell/view/frame

The frame is implemented as four top level windows that cover the border of the screen when visible. Every side of the frame contains icons organized in trays (gtk.Toolbar). See OLPC Human Interface Guidelines/The Laptop Experience/The Frame.

Code: http://dev.laptop.org/git?p=sugar;a=tree;f=shell/view/home

The home view is a top-level window with the DESKTOP hint. The three zoom levels are implemented as hippo.Canvas embedded in that window. See OLPC Human Interface Guidelines/The Laptop Experience/Zoom Metaphor.

Activities

What are called applications or programs in other environments, are activities in Sugar, see OLPC Human Interface Guidelines/Activities.

Activity authors need to understand how the activity concept is different from traditional applications and how its software can make better use of the Sugar platform.

Activities can happen in isolation or in collaboration with other users.

What is a correct activity from the implementation point of view:

Activities can choose between using the low level APIs presented above, or the higher-level Sugar_Architecture#Activity_API presented below.

Shell service

Code: http://dev.laptop.org/git?p=sugar;a=tree;f=services/shell

The shell service provides the following subservices to the Shell:

  • clipboard: store clippings, this is basically the backend of the clipboard tray in the left frame,
  • activity registry: manages a registry of the installed activities,
  • object type registry: maintains a mapping of mime type to "umbrella" types, these are high level object types like Image, Audio, Video, etc that are used to give the user an uniform view of objects in the clipboard and in the journal.

These services are offered as D-Bus interfaces.

Journal

Code: http://dev.laptop.org/git?p=journal-activity;a=tree

The Journal keeps track of what the user has done with the laptop. Every activity should keep records in the journal so the user can see what has been done in the past and probably resume some past activity.

All this data produced by the activities is kept by the Datastore service, and the journal provides to the user different ways of querying and browsing past works.

Datastore service

Code: http://dev.laptop.org/git?p=projects/datastore;a=tree

Provides activities with a way to store data and metadata and the journal with means for querying, including full text search.

Presence service

Code: http://dev.laptop.org/git?p=projects/presence-service;a=tree

See Presence Service.

Activity API

Code: http://dev.laptop.org/git?p=sugar;a=tree;f=lib

This API aims to make the development of new activities as simple and straightforward as possible.

Currently it is only available to activities implemented in python, but the plan is to gradually rewrite it in C and make available bindings for different languages.

TODO: link to the activity API pydocs

Contains the following modules:

Specifications

API

Third party packages

Links and references

Python Documentation

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