Use Case
You have content you would like to provide to the user to enrich the presentation or experience of the main content. It could be something to experience before the user chooses to start interacting with the main content and/or something additional to consider while interacting with the main content. You might want to have an image available while an audio-only Canvas is playing or, conversely, audio available while a user is navigating an image-only Manifest.
Implementation notes
Across a Manifest and its properties, you may use more than one accompanyingCanvas
, allowing you to have an authentic accompanyingCanvas
for each appropriate resource (Collection, Manifest, Canvas, and Range).
The target
of the Annotation
of an accompanyingCanvas
should have as its value the id
of the accompanyingCanvas
, not the id
of the resource that has the accompanyingCanvas
.
Always keep in mind the wide latitude given conforming clients: It is up to the client whether and in what sort of UI to display content you place in a accompanyingCanvas
property. Don’t use this property for content that must be displayed. On the other hand, placing content in a accompanyingCanvas
does tell a client that the content, if displayed, should be displayed at the same time as the resource to which it is attached.
Restrictions
Each instance of accompanyingCanvas
may only contain one Canvas, and as such may specifically not contain an additional accompanyingCanvas
or a placeholderCanvas
.
Example
In the example, the main Canvas contains audio of a performance of Gustav Mahler’s Symphony No. 3 and the accompanyingCanvas
contains an image of a page from the score.
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Related recipes
- Simplest Manifest - Video
- Load a Preview Image Before the Main Content, using
placeholderCanvas
to present one resource ahead of another.