Enum DispatchPolicy

#[repr(u32)]
pub enum DispatchPolicy {
    ExclusiveTarget = 1,
    TopHitAndAncestorsInTarget = 2,
    MouseHoverAndLatchInTarget = 3,
}

A specification of the UI clients that may have injected events dispatched to them in an |Target|. One is specified in |Config|.

A useful concept is “latching”, where one or more clients may start receiving the pointer event stream, prior to assignment of stream ownership. After ownership is assigned (e.g., through a gesture disambiguation protocol), non-owning clients have their latch terminated – they stop receiving the pointer event stream.

• A client’s latch does not itself confer stream ownership (receiving the entire pointer event stream); gesture disambiguation or device termination may prematurely end the stream dispatched to that client.
• It’s possible for a client to latch while hidden from the user (i.e., manipulate a surface that is invisible to the user), where the occluding surface is owned by a client outside of |Target|. Conversely, these occluding clients cannot latch, because latched clients must be in |Target|’s view tree.

Variants

ExclusiveTarget = 1

A single client latches onto a pointer event stream, where:

• the pointer event stream starts within the viewport rectangle,
• the latch happens on the ADD phase of the pointer event stream,
• the client is the |Target| itself. Ownership is assigned immediately to the client.

Note: This policy guarantees confidentiality, integrity, and availability of dispatch to the client, but by itself, does not confer immunity against UI redress attacks.

TopHitAndAncestorsInTarget = 2

Multiple clients may latch onto a pointer stream, where:

• the pointer stream starts within the viewport rectangle,
• a hit test is performed on the ADD phase of the pointer event stream, which returns the top-most surface (in paint order) in the |Target|’s view tree,
• the top-most surface’s client latches onto the pointer stream,
• the client’s ancestors in the |Target|’s view tree also latch onto the pointer stream.

With multiple latches, a pointer stream is dispatched in parallel to each latched client, until ownership is assigned via gesture disambiguation. The owner client will continue to receive the pointer stream, and non-owners will receive a final CANCEL event for the stream.

Note: It’s possible for no clients to latch, if the hit test fails to hit any surface in any sub-view of |Target|. Note: Each client will have its own copy of the viewport, placed accordingly in its own coordinate system.

MouseHoverAndLatchInTarget = 3

The top hit client in the |Target|’s view tree receives hover events when a cursor is positioned over it, unless the mouse is latched to a specific client.

A mouse initiates a latch via button down, and until the release of that latch, mouse events are delivered to that latched client; other clients do not receive hover events in the latch duration.

Note: It’s possible for no client to latch, if the hit test fails to hit any surface in any sub-view of |Target|. Note: Each client will have its own copy of the viewport, placed accordingly in its own coordinate system.

Implementations

impl DispatchPolicy

pub fn from_primitive(prim: u32) -> Option<Self>

pub const fn into_primitive(self) -> u32

pub fn is_unknown(&self) -> bool

👎Deprecated: Strict enums should not use is_unknown

Trait Implementations

impl Clone for DispatchPolicy

fn clone(&self) -> DispatchPolicy

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DispatchPolicy

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

Formats the value using the given formatter.

impl<D: ResourceDialect> Decode<DispatchPolicy, D> for DispatchPolicy

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<'_, D>, offset: usize, _depth: Depth, ) -> Result<()>

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

impl<D: ResourceDialect> Encode<DispatchPolicy, D> for DispatchPolicy

unsafe fn encode( self, encoder: &mut Encoder<'_, D>, 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 DispatchPolicy

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 DispatchPolicy

fn cmp(&self, other: &DispatchPolicy) -> 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 DispatchPolicy

fn eq(&self, other: &DispatchPolicy) -> 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 DispatchPolicy

fn partial_cmp(&self, other: &DispatchPolicy) -> 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 TypeMarker for DispatchPolicy

type Owned = DispatchPolicy

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 ValueTypeMarker for DispatchPolicy

type Borrowed<'a> = DispatchPolicy

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

fn borrow(value: &<Self as TypeMarker>::Owned) -> Self::Borrowed<'_>

Cheaply converts from &Self::Owned to Self::Borrowed.

impl Copy for DispatchPolicy

impl Eq for DispatchPolicy

impl StructuralPartialEq for DispatchPolicy