Struct ViewRef

pub struct ViewRef {
    pub reference: EventPair,
}

A ViewRef is a handle to a kernel object which identifies a unique View across the system. Two ViewRefs to the same View have the same KOID.

Clients use a ViewRef to identify a View, to validate a View, and to receive a View invalidation signal.

As part of View creation, the client creates a linked ViewRef/ViewRefControl pair and hands the pair to Scenic (ViewRefControl is described below). The client must remove the ViewRef’s signal capabilities; otherwise the View is not created.

The client may freely clone its ViewRef and share it, even before sending it to Scenic.

Example 1. Accessibility accepts a ViewRef from a client to group the semantic nodes, and semantic operations, associated with a client’s View. It must validate a client’s ViewRef with Scenic.

Example 2. We use ViewRefs to create a FocusChain, which identifies Views considered as “in-focus” down the View hierarchy. When a View is destroyed, Scenic signals to all FocusChain holders that the ViewRef is now invalid.

Fields

reference: EventPair

Trait Implementations

impl Debug for ViewRef

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Decode<ViewRef, DefaultFuchsiaResourceDialect> for ViewRef

fn new_empty() -> Self

Creates a valid instance of Self. The specific value does not matter, since it will be overwritten by decode.

unsafe fn decode( &mut self, decoder: &mut Decoder<'_, DefaultFuchsiaResourceDialect>, offset: usize, _depth: Depth, ) -> Result<()>

Decodes an object of type T from the decoder’s buffers into self.

impl Encode<ViewRef, DefaultFuchsiaResourceDialect> for &mut ViewRef

unsafe fn encode( self, encoder: &mut Encoder<'_, DefaultFuchsiaResourceDialect>, offset: usize, _depth: Depth, ) -> Result<()>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID.

impl<T0: Encode<HandleType<EventPair, { _ }, 2147483648>, DefaultFuchsiaResourceDialect>> Encode<ViewRef, DefaultFuchsiaResourceDialect> for (T0,)

unsafe fn encode( self, encoder: &mut Encoder<'_, DefaultFuchsiaResourceDialect>, offset: usize, depth: Depth, ) -> Result<()>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID.

impl Hash for ViewRef

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for ViewRef

fn cmp(&self, other: &ViewRef) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for ViewRef

fn eq(&self, other: &ViewRef) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for ViewRef

fn partial_cmp(&self, other: &ViewRef) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl ResourceTypeMarker for ViewRef

type Borrowed<'a> = &'a mut ViewRef

The Rust type to use for encoding. This is a particular Encode<Self> type cheaply obtainable from &mut Self::Owned. There are three cases:

fn take_or_borrow<'a>( value: &'a mut <Self as TypeMarker>::Owned, ) -> Self::Borrowed<'a>

Cheaply converts from &mut Self::Owned to Self::Borrowed. For HandleBased types this is “take” (it returns an owned handle and replaces value with Handle::invalid), and for all other types it is “borrow” (just converts from one reference to another).

impl TypeMarker for ViewRef

type Owned = ViewRef

The owned Rust type which this FIDL type decodes into.

fn inline_align(_context: Context) -> usize

Returns the minimum required alignment of the inline portion of the encoded object. It must be a (nonzero) power of two.

fn inline_size(_context: Context) -> usize

Returns the size of the inline portion of the encoded object, including padding for alignment. Must be a multiple of inline_align.

fn encode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and encoding requires no validation. When true, we can optimize encoding arrays and vectors of Self::Owned to a single memcpy.

fn decode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and decoding requires no validation. When true, we can optimize decoding arrays and vectors of Self::Owned to a single memcpy.

impl Eq for ViewRef

impl Standalone<DefaultFuchsiaResourceDialect> for ViewRef

impl StructuralPartialEq for ViewRef