1 Content Management & Exchange {#mainpage}
2 =============================
4 Unity and the overall Ubuntu experience put heavy emphasis on the
5 notion of content, with Unity’s dash offering streamlined access to
6 arbitrary content, both local to the device or online. More to this,
7 Unity’s dash is the primary way of surfacing content on mobile form
8 factors without the need to access individual applications and their
9 respective content silos. The content-hub deals with
10 application-specific content management and implements an architecture
11 that allows an app to define its own content silo, exchange content
12 with other applications/the system, and a way to provide the user with
13 content picking functionality.
15 To ease conversations, we start over with a set of definitions:
17 - Content item: A content item is an entity that consists of meta-data
18 and data. E.g., an image is a content item, where the actual pixels
19 are the data, and information like size, image format, bit depth,
20 location etc. is considered meta data. \sa com::ubuntu::content::Item.
22 - Content types: A set of well-known content types. E.g., images or
23 music files. \sa com::ubuntu::content::Type.
25 - Content set: A set of unique content items. Can be considered a
26 content item itself, e.g., in the case of playlists.
28 - Content owner: The unique owner of a content item. A content item
29 has to be owned by exactly one app. \sa com::ubuntu::content::Peer
31 - Content store: A container (think of it as a top-level folder in
32 the filesystem) that contains content items of a certain
33 type. Different stores exist for different scopes, where scope
34 refers to either system-wide, user-wide or app-specific storage
35 locations. \sa com::ubuntu::content::Store, com::ubuntu::content::Scope
37 - Content transfer: Transferring content item/s to and from a source
38 or destination. A transfer is uniquely defined by:
40 * The content destination
41 * The transfer direction, either import or export
42 * The set of items that should be exchanged
43 \sa com::ubuntu::content::Transfer, com::ubuntu::content::Hub::create_import_for_type_from_peer
45 - Content picking: Operation that allows a user to select content for
46 subsequent import from a content source (e.g., an application). The
47 content source is responsible for providing a UI to the user.
49 Architectural Overview
50 ----------------------
52 The architecture enforces complete application isolation, both in
53 terms of content separation, sandboxing/confinement and in terms of
54 the application lifecycle. As we cannot assume that two apps that want
55 to exchange content are running at the same time, a system-level
56 component needs to mediate and control the content exchange operation,
57 making sure that neither app instance assumes the existence of the
58 other one. We refer to this component as the content hub. \sa com::ubuntu::content::Hub
60 Example usage - Importing Pictures
61 ----------------------------------
63 \snippet acceptance-tests/app_hub_communication_transfer.cpp Importing pictures