Defaults

A diagram opens on its first view, on its overview, with every scenario waiting to be chosen. The defaults: block changes that for one diagram, in the file that describes it, so every page that shows the diagram opens it the same way.

This diagram opens on the sign-in scenario, drawn as a sequence diagram, with the panel folded to its button:

defaults:
  scenario: sign-in
  mode: sequence
  sidebar: false

Fields

Field	Meaning
`view`	The view shown first. Without it, the view of `scenario`, then the first view.
`scenario`	The scenario selected first. Without it the diagram opens on its overview. It waits for the reader to press play, unless `autoplay` is on.
`mode`	How a scenario is drawn when it has no `mode` of its own: `flow` (packets over the diagram), `sequence` or `story`.
`sidebar`	Whether the panel over the picture, with the outline and the views, starts open. Without it, the panel starts open when there is another view to choose.
`subtitles`	Whether the step’s title and description show on the bar while the scenario plays. On by default.
`autoplay`	Play `scenario` as soon as the diagram is on screen. It needs a `scenario`, and readers who ask their system for reduced motion are never autoplayed.

Every field is optional. The compiler checks that view and scenario exist, and that a scenario named with a view plays on that view.

Who decides

The page that shows a diagram can always choose otherwise. From the strongest to the weakest:

The reader. A link to a scenario and step (#checkout=place-order.3) opens there, and the controls change anything.
The page. The props of <Diagram>: view, scenario, mode, autoplay, sidebar and subtitles. A page that names a view that the default scenario does not play on opens that view with nothing selected.
The scenario. Its own mode: wins over defaults.mode.
The diagram’s defaults.
What idocs does without being told.

HTTP request / responseData access

Loading diagram…

Pick a scenario to watch it play.

This is the same diagram, shown with view="auth-path" mode="story" sidebar. The page asked for another view, so the default scenario, which plays on the overview, is left out, and the panel is open.

Things to know

The mode sticks. Choosing a scenario that names no mode keeps the mode the reader is in, so someone who switched to the sequence view stays there. Going back to the overview returns to defaults.mode.
A narrow widget still folds the panel. sidebar: true in the file means “open when there is room”. A widget under about 640 px starts folded unless the page passes sidebar itself.
Links stay quiet. The address bar records where the reader is only when it differs from how the diagram opens, so a default scenario does not rewrite the URL of every page that shows it. Choosing the overview of a diagram that opens on a scenario is recorded as #name=~.
Nested diagrams use their own. A diagram that is shown in place or opened from a node takes the view and scenario that node names, and otherwise opens as its own defaults say. autoplay only applies to a diagram on a page, not one opened from another.