Struct FocusChain

pub struct FocusChain {
    pub focus_chain: Option<Vec<ViewRef>>,
    /* private fields */
}

A FocusChain tracks the status of the View hierarchy as View focus changes.

Reception. Only certain components may receive a FocusChain, as it captures global information about the scene graph.

Fields

focus_chain: Option<Vec<ViewRef>>

The focus_chain is reported in order of dominance in the View hierarchy; each adjacent pair of elements represents a parent-child relationship.

The focus_chain MAY be unset when FocusChain message is received, if the message is sent very early in the scene setup, before the first view is available.

When focus_chain is set, however, the root View is always present and occupies slot 0 in the focus_chain. The newly-focused View receives a fuchsia.ui.input.FocusEvent and occupies the final slot in the vector.

If a View gets destroyed, a FocusChain holder that listens will receive a ZX_EVENTPAIR_PEER_CLOSED signal on the corresponding ViewRef.

Invalidation.

A FocusChain is invalid if any one if its ViewRefs is invalid.

Trait Implementations

impl Debug for FocusChain

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

Formats the value using the given formatter.

impl Decode<FocusChain, DefaultFuchsiaResourceDialect> for FocusChain

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 Default for FocusChain

fn default() -> FocusChain

Returns the “default value” for a type.

impl Encode<FocusChain, DefaultFuchsiaResourceDialect> for &mut FocusChain

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 PartialEq for FocusChain

fn eq(&self, other: &FocusChain) -> 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 ResourceTypeMarker for FocusChain

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

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 FocusChain

type Owned = FocusChain

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 Standalone<DefaultFuchsiaResourceDialect> for FocusChain

impl StructuralPartialEq for FocusChain