fuchsia.element

PROTOCOLS

AnnotationController

Defined in fuchsia.element/annotations.fidl

An interface to create, read, update, and delete annotations, typically on an element or its view.

GetAnnotations

Returns the current Annotations for the element.

• error GetAnnotationsError if the annotations could not be returned.

Request

<EMPTY>

Response

Name	Type
result	AnnotationController_GetAnnotations_Result

UpdateAnnotations

Adds, updates, and removes annotations.

The server is expected to adhere to the following conventions:

• If a key in annotations_to_set is new, a new annotation is added
• If a key in annotations_to_set already exists, the annotation value is updated
• If a key in annotations_to_delete does not exist, it is ignored

The same key cannot appear twice in a call to UpdateAnnotations(). In other words, to set two Annotations with matching keys is illegal, as is an attempt to set an Annotation and also delete it.

If the operation results in an error, the annotations remain unchanged, and will not be partially updated.

• error UpdateAnnotationsError.INVALID_ARGS if the same key exists in both annotations_to_set and annotations_to_delete.
• error UpdateAnnotationsError.INVALID_ARGS if a key in annotations_to_set or annotations_to_delete has an empty namespace.
• error UpdateAnnotationsError.INVALID_ARGS if an AnnotationValue.buffer in annotations_to_set could not be read.
• error UpdateAnnotationsError.TOO_MANY_ANNOTATIONS if the operation results in more than MAX_ANNOTATIONS_PER_ELEMENT annotations existing.

Request

Name	Type
annotations_to_set	Annotations
annotations_to_delete	AnnotationKeys

Response

Name	Type
result	AnnotationController_UpdateAnnotations_Result

WatchAnnotations

Returns annotations when they have changed, or when this method is called by the client for the first time.

This operation does not block other requests from the client, but only one WatchAnnotations request at a time can be made on a connection. If the client makes a second WatchAnnotations request before waiting for the previous request to complete, the connection will be closed.

• error WatchAnnotationsError if the annotations could not be returned.

Request

<EMPTY>

Response

Name	Type
result	AnnotationController_WatchAnnotations_Result

Controller

Defined in fuchsia.element/element_manager.fidl

An interface that gives clients of Manager (element proposers) control over the proposed element's lifecycle and annotations.

Lifecycle

The client must keep Controller connected to ensure the element remains in the session and is not destroyed. Once Controller is closed, the element and its component will be terminated. The element may also terminate itself, which will cause Controller to close.

GetAnnotations

Returns the current Annotations for the element.

• error GetAnnotationsError if the annotations could not be returned.

Request

<EMPTY>

Response

Name	Type
result	AnnotationController_GetAnnotations_Result

UpdateAnnotations

Adds, updates, and removes annotations.

The server is expected to adhere to the following conventions:

• If a key in annotations_to_set is new, a new annotation is added
• If a key in annotations_to_set already exists, the annotation value is updated
• If a key in annotations_to_delete does not exist, it is ignored

The same key cannot appear twice in a call to UpdateAnnotations(). In other words, to set two Annotations with matching keys is illegal, as is an attempt to set an Annotation and also delete it.

If the operation results in an error, the annotations remain unchanged, and will not be partially updated.

• error UpdateAnnotationsError.INVALID_ARGS if the same key exists in both annotations_to_set and annotations_to_delete.
• error UpdateAnnotationsError.INVALID_ARGS if a key in annotations_to_set or annotations_to_delete has an empty namespace.
• error UpdateAnnotationsError.INVALID_ARGS if an AnnotationValue.buffer in annotations_to_set could not be read.
• error UpdateAnnotationsError.TOO_MANY_ANNOTATIONS if the operation results in more than MAX_ANNOTATIONS_PER_ELEMENT annotations existing.

Request

Name	Type
annotations_to_set	Annotations
annotations_to_delete	AnnotationKeys

Response

Name	Type
result	AnnotationController_UpdateAnnotations_Result

WatchAnnotations

Returns annotations when they have changed, or when this method is called by the client for the first time.

This operation does not block other requests from the client, but only one WatchAnnotations request at a time can be made on a connection. If the client makes a second WatchAnnotations request before waiting for the previous request to complete, the connection will be closed.

• error WatchAnnotationsError if the annotations could not be returned.

Request

<EMPTY>

Response

Name	Type
result	AnnotationController_WatchAnnotations_Result

GraphicalPresenter

Defined in fuchsia.element/graphical_presenter.fidl

An interface used to present graphical views.

The GraphicalPresenter protocol is typically implemented by a session component or its child that presents element views.

The presented views can be annotated with fuchsia.element.Annotations to communicate presentation properties to the GraphicalPresenter.

PresentView

Presents the view described by view_spec.

ViewController

view_controller allows clients to receive a ViewController for the presented view. The client can use the ViewController to control the view's presentation and receive events.

If view_controller is closed, the client can assume that the view is no longer being presented, and will not be presented in the future.

If the client closes the view_controller, or does not provide a request to PresentView, the view may be dismissed at any time with no signal to the client.

Errors

PresentView errors are signaled by closing view_controller with an epitaph, ViewControllerEpitaph. See ViewController.

• view_spec describes the view to present
• annotation_controller a handle to make changes to the respective element's annotations
• view_controller_request an optional request for a controller for the view

• error view_spec must contain view_holder_token and view_ref for Gfx views, OR viewport_creation_token for Flatland views, but never both. If both are set, error PresentViewError.INVALID_ARGS is thrown.
• error PresentViewError.INVALID_ARGS if spec.view_holder_token or spec.view_ref are missing or invalid
• error PresentViewError if the view could not be presented

Request

Name	Type
view_spec	ViewSpec
annotation_controller	AnnotationController?
view_controller_request	server_end<ViewController>?

Response

Name	Type
result	GraphicalPresenter_PresentView_Result

Manager

Defined in fuchsia.element/element_manager.fidl

An interface used to add elements to a session.

An element is a component that is expected to be instantiated as a child of the session and to interact with the user in some way. An element proposer is a component that calls ProposeElement to add an element to the session.

The session will typically implement Manager and provide it to its child element proposers.

For example, an element proposer may be a non-interactive application that listens to the network for a command to display an element to the user. When it receives the command, the element proposer proposes to add an element to the session via the Manager protocol. Similarly, the element proposer may be part of an interactive user interface that proposes elements based on user input.

ProposeElement

Proposes to add an element to the session.

If ProposeElement returns without error, the caller can assume the element is now part of the session. However, whether or not the element component is actively running, or not, depends on the session implementation. For example, a session may decide to conserve resources by suspending an element which is not visible, or delay the running of an element until a more appropriate time.

Spec

• spec.component_url is required

If spec.additional_services is specified,

• spec.component_url must point to a CFv1 component (additional_services is not supported for CFv2 components)

• The fuchsia.sys/ServiceList.host_directory field in spec.additional_services must be set to a channel to a directory hosting the services (fuchsia.sys/ServiceList.provider is not supported and must be null)

If spec.arguments is specified,

• spec.component_url must point to a CFv1 component (arguments is not supported for CFv2 components)

• spec describes the element to add
• controller can be used to observe and affect the lifecycle of the element, and to set and get annotations on the element

• error ProposeElementError.NOT_FOUND if spec.component_url is missing or could not be resolved
• error ProposeElementError.INVALID_ARGS if spec.additional_services:
  • is specified for a CFv2 spec.component_url, or
  • does not have a valid fuchsia.sys/ServiceList.host_directory, or
  • contains a non-null fuchsia.sys/ServiceList.provider if spec.arguments:
  • is specified for a CFv2 spec.component_url

Request

Name	Type
spec	Spec
controller	server_end<Controller>?

Response

Name	Type
result	Manager_ProposeElement_Result

ViewController

Defined in fuchsia.element/graphical_presenter.fidl

An interface that gives clients of GraphicalPresenter control over a view that was presented.

Lifecycle

The client must keep ViewController connected to ensure the view is presented. Once ViewController is closed, the view will be permanently dismissed.

For example, if the view originates from an element, the component that manages the element's lifecycle may choose to stop the element's component once the ViewController is closed.

Epitaph

This protocol is closed with an epitaph:

• ZX_OK when the view is dismissed

Dismiss

Instructs the presenter to dismiss the associated view.

This call results in the ViewController being closed with a ZX_OK epitaph once any exit animation has been performed, the view/view holder connection has been severed, and the component instance serving the view can be terminated.

Request

<EMPTY>

OnPresented

Informs the view controller that the view was presented successfully.

Response

<EMPTY>

STRUCTS

Annotation resource

Defined in fuchsia.element/annotations.fidl

An annotation defined dynamically by key/value pair.

The Session Framework does not constrain the contents of key and value in any way. Cooperating components that exchange annotations must define and validate annotation entries based on their own conventions.

Field	Type	Description	Default
key	AnnotationKey	An identfier for this annotation.	No default
value	AnnotationValue	The content of this annotation.	No default

AnnotationController_GetAnnotations_Response resource

Defined in fuchsia.element/annotations.fidl

Field	Type	Description	Default
annotations	Annotations		No default

AnnotationController_UpdateAnnotations_Response

Defined in fuchsia.element/annotations.fidl

<EMPTY>

AnnotationController_WatchAnnotations_Response resource

Defined in fuchsia.element/annotations.fidl

Field	Type	Description	Default
annotations	Annotations		No default

AnnotationKey

Defined in fuchsia.element/annotations.fidl

The key of an fuchsia.element/Annotation.

Field	Type	Description	Default
namespace	string[128]	A namespace that disambiguates groups of keys across clients. This is intended to group related keys together under the same identifier, and avoid naming collisions. For example, a session may use a custom namespace to define annotations that are specific to its implementation. The namespace is required and must be non-empty. The namespace "global" is represents the global namespace, reserved for annotations common across many products and session components. To ensure compatibility, clients should use a unique namespace, like a UUID or the client's component URL, when introducing new keys.	No default
value	string[128]	An identifier for this annotation, uniquely identifying the annotation within namespace.	No default

GraphicalPresenter_PresentView_Response

Defined in fuchsia.element/graphical_presenter.fidl

<EMPTY>

Manager_ProposeElement_Response

Defined in fuchsia.element/element_manager.fidl

<EMPTY>

ENUMS

GetAnnotationsError strict

Type: uint32

Defined in fuchsia.element/annotations.fidl

An error returned from ElementController/GetAnnotations.

Name	Value	Description
BUFFER_READ_FAILED	1	The AnnotationValue.buffer of an annotation could not be read.

PresentViewError strict

Type: uint32

Defined in fuchsia.element/graphical_presenter.fidl

An error returned when GraphicalPresenter fails to present a view.

Name	Value	Description
INVALID_ARGS	1	The provided ViewSpec is malformed.

ProposeElementError strict

Type: uint32

Defined in fuchsia.element/element_manager.fidl

Errors that can be returned when attempting to add elements to a session.

Name	Value	Description
INVALID_ARGS	1	The element spec was malformed.
NOT_FOUND	2	The element's component URL could not be resolved.

UpdateAnnotationsError strict

Type: uint32

Defined in fuchsia.element/annotations.fidl

An error returned from AnnotationController/UpdateAnnotations

Name	Value	Description
INVALID_ARGS	1	The arguments passed to UpdateAnnotations are malformed.
TOO_MANY_ANNOTATIONS	2	The total number of annotations will exceed MAX_ANNOTATIONS_PER_ELEMENT as a result of updating the annotations.

WatchAnnotationsError flexible

Type: uint32

Defined in fuchsia.element/annotations.fidl

An error returned from AnnotationController/WatchAnnotations and ElementController/WatchAnnotations.

Name	Value	Description
BUFFER_READ_FAILED	1	The AnnotationValue.buffer of an annotation could not be read.

TABLES

Spec resource

Defined in fuchsia.element/element_manager.fidl

Description of an element to be added to a session.

Ordinal	Field	Type	Description
1	component_url	fuchsia.url/Url	The component URL of the element. Required.
2	annotations	Annotations	Initial annotations on the element. Required, but can be an empty vector.
3	additional_services	fuchsia.sys/ServiceList	A list of services passed to the Element. Optional.
4	arguments	vector<string>	Arguments provided to the component. Optional.

ViewSpec resource

Defined in fuchsia.element/graphical_presenter.fidl

A description of a view that can be presented by a GraphicalPresenter.

Ordinal	Field	Type	Description
1	view_holder_token	fuchsia.ui.views/ViewHolderToken	The view holder token for the presented Gfx view. Must be unset for Flatland views.
2	view_ref	fuchsia.ui.views/ViewRef	The ViewRef of the presented Gfx view. Must be unset for Flatland views.
4	viewport_creation_token	fuchsia.ui.views/ViewportCreationToken	The viewport creation token for the presented Flatland view. Must be unset for Gfx views.
3	annotations	Annotations	The annotations associated with the presented view. The presenter must observe incoming annotations and update the presentation accordingly. For views that come from elements, the annotations are expected to be the same as the annotations for the element. For example, if the GraphicalPresenter component uses ElementManager to add an element to the session, and gives it an annotation, the presenter can expect that annotation to be passed back in ViewSpec.annotations for the associated view. Optional.

UNIONS

AnnotationController_GetAnnotations_Result strict resource

Defined in fuchsia.element/annotations.fidl

Ordinal	Variant	Type	Description
1	response	AnnotationController_GetAnnotations_Response
2	err	GetAnnotationsError

AnnotationController_UpdateAnnotations_Result strict

Defined in fuchsia.element/annotations.fidl

Ordinal	Variant	Type	Description
1	response	AnnotationController_UpdateAnnotations_Response
2	err	UpdateAnnotationsError

AnnotationController_WatchAnnotations_Result strict resource

Defined in fuchsia.element/annotations.fidl

Ordinal	Variant	Type	Description
1	response	AnnotationController_WatchAnnotations_Response
2	err	WatchAnnotationsError

AnnotationValue strict resource

Defined in fuchsia.element/annotations.fidl

The value of an fuchsia.element/Annotation.

The actual field used depends on the type of annotation.

Ordinal	Variant	Type	Description
1	text	string
2	buffer	fuchsia.mem/Buffer

GraphicalPresenter_PresentView_Result strict

Defined in fuchsia.element/graphical_presenter.fidl

Ordinal	Variant	Type	Description
1	response	GraphicalPresenter_PresentView_Response
2	err	PresentViewError

Manager_ProposeElement_Result strict

Defined in fuchsia.element/element_manager.fidl

Ordinal	Variant	Type	Description
1	response	Manager_ProposeElement_Response
2	err	ProposeElementError

CONSTANTS

Name	Value	Type	Description
MAX_ANNOTATIONS_PER_ELEMENT	1024	uint32	Maximum number of annotations for a single element or view.
MAX_ANNOTATION_KEY_NAMESPACE_SIZE	128	uint32	Maximum length of AnnotationKey.namespace.
MAX_ANNOTATION_KEY_VALUE_SIZE	128	uint32	Maximum length of AnnotationKey.value.

TYPE ALIASES

Name	Value	Description
AnnotationKeys	vector[MAX_ANNOTATIONS_PER_ELEMENT]	A list of annotation keys.
Annotations	vector[MAX_ANNOTATIONS_PER_ELEMENT]	A list of annotations on an element.