Adaptive Card Renderer Specification

The following specification describes how implement an Adaptive Card renderer on any UI platform.

Important

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SDK Versioning

  1. The SDK major and minor version SHOULD match the schema version.
  2. Patch/build SHOULD be used for renderer updates that don't have schema changes.

Parsing JSON

Error conditions

  1. A parser MUST check that it's valid JSON content
  2. A parser MUST validate against the schema (required properties, etc)
  3. The above errors MUST be reported to the host app (exception or equivalent)

Unknown types

  1. If unknown "types" are encountered they MUST BE DROPPED from the result
  2. Any alterations of the payload (like above) SHOULD be reported as warnings to the host app

Unknown properties

  1. A parser MUST include additional properties on elements

Additional considerations

  1. The speak property may contain SSML markup and MUST be returned to the host app as-specified

Parsing Host Config

  1. TODO

Versioning

  1. A renderer MUST implement a particular version of the schema.
  2. The AdaptiveCard constructor MUST give the Version property a default value based on the current schema version
  3. If a renderer encounters a minRequiredVersion property in the AdaptiveCard that is higher than the supported version, it MUST return the fallbackText instead.

Rendering

An AdaptiveCard consists of a body and actions. The body is a collection of CardElements that a renderer will enumerate and render in order.

  1. Each Element MUST stretch to the width of its parent (think display: block in HTML).
  2. A renderer MUST ignore unknown element types, and continue rendering the rest of the payload.

Spacing and Separators

  1. The spacing property on every element influences the amount of space between the CURRENT element and the one BEFORE it.
  2. Spacing MUST ONLY apply when there actually is an element preceding it. (E.g., won't apply to the first item in an array)
  3. A renderer MUST look up the amount of space to use from the hostConfig spacing for the enum value applied to the current element.
  4. If the element has a separator value of true, then a visible line MUST be drawn between the current element and the one before it.
  5. The separator line MUST be drawn using the container.style.default.foregroundColor.
  6. A separator MUST ONLY be drawn if the item IS NOT the first in the array.

Columns

  1. Column width MUST be interpreted by "auto", "stretch" or a weighted ratio.

TextBlock

  1. A TextBlock MUST take up a single line unless the wrap property is true.
  2. The text block SHOULD trim any excess text with an ellipsis (...)

Markdown

  1. Adaptive Cards allow for a subset of Markdown and SHOULD be supported in TextBlock.
  2. See full markdown requirements

Formatting functions

  1. TextBlock allows DATE/TIME formatting functions that MUST be supported on every renderer.
  2. ALL FAILURES MUST display the raw string in the card. No friendly message attempted. (The goal being to make the developer immediately aware there is a problem)

  3. TODO: Include regex

Images

  1. A renderer SHOULD allow host apps to know when all HTTP images have been downloaded and the card is "fully rendererd"
  2. A renderer MUST inspect the Host Config maxImageSize param when downloading HTTP images
  3. A renderer MUST support .png and .jpeg
  4. A renderer SHOULD support .gif images

Host Config

  • TODO: What should the defaults be? Should they all share it? Should we embed a common hostConfig.json file in the binaries?
  • TODO: I think HostConfig needs to be versioned as well for parsing?

HostConfig is a shared configuration object that specifies how an Adaptive Card Renderer generates UI.

This allows properties which are platform agnostic to be shared among renderers on different platforms and devices. It also allows tooling to be created which gives you an idea of the look and feel that card would have for a given environment.

  1. Renderers MUST expose a Host Config parameter to host apps
  2. All elements MUST be styled according to their respective Host Config settings

Native platform styling

  1. Each element type SHOULD attach a native platform style with the generated UI element. E.g., in HTML we added a CSS class to the element types, and in XAML we assign a specific Style.

Extensbility

  1. A renderer MUST allow host apps to override default element renderers. E.g., replace TextBlock rendering with their own logic.
  2. A renderer MUST allow host apps to register custom element types. E.g., add support for a custom Rating element
  3. A renderer MUST allow host apps to remove support for a default element. E.g., remove Action.Submit if they don't want it supported.

Actions

  1. If HostConfig supportsInteractivity is false, a renderer MUST NOT render any actions.
  2. The actions property MUST be rendered as buttons in some kind of action bar, usually at the bottom of the card.
  3. When a button is tapped it MUST allow the host app to handle the event.
  4. The event MUST pass along all associated properties with the action
  5. The event MUST pass along the AdaptiveCard which was executed
Action Behavior
Action.OpenUrl Open an external URL for viewing
Action.ShowCard Requests a sub-card to be shown to the user.
Action.Submit Ask for all of the input elements to be gathered up into an object which is then sent to you through some method defined by the host application.

Action.OpenUrl

  1. Action.OpenUrl SHOULD open a URL using the native platform mechanism
  2. If this is not possible it MUST raise an event to the host app to handle opening the URL. This event MUST allow the host app to override the default behavior. E.g., let them open the URL within their own app.

Action.ShowCard

  1. Action.ShowCard MUST be supported in some way, based on the hostConfig setting. There are two modes: inline, and popup. Inline cards SHOULD toggle the card visibility automatically. In popup mode, an event SHOULD be fired to the host app to show the card in some way.

Action.Submit

The Submit Action behaves like an HTML form submit, except that where HTML typically triggers an HTTP post, Adaptive Cards leaves it up to each host app to determine what "submit" means to them.

  1. When this MUST raise an event the user taps the action invokved.
  2. The data property MUST be included in the callback payload.
  3. For Action.Submit, a renderer MUST gather all inputs on the card and retrieve their values.

selectAction

  1. If Host Config supportedInteractivity is false then a selectAction MUST NOT render as a touch target.
  2. Image, ColumnSet, and Column offer a selectAction property, which SHOULD be executed when the user invokes it, e.g., by tapping the element.

Inputs

  1. If HostConfig supportsInteractivity is false a renderer MUST NOT render any inputs.
  2. Inputs SHOULD render with the highest fidelity possible. For example, an Input.Date would ideally offer a date picker to a user, but if this isn't possible on your UI stack, then the renderer MUST fall back to rendering a standard text box.
  3. A renderer SHOULD display the placeholderText if possible
  4. A renderer DOES NOT have to implement validation of the input. Users of Adaptive Cards must plan to validate any receieved data on their end.
  5. Input value binding MUST be properly escaped

  6. The object MUST be returned to the host app as follows:

    We do not make any promises of input validation in adaptive cards, so it's up to the receiving party to properly parse the response. E.g., a Input.Number could return "hello" and they need to be prepared for that.

Events

  1. A renderer SHOULD fire an event when an element's visibility has changed, allowing the host app to scroll the card into position.