Struct Viewport

pub struct Viewport {
    pub extents: Option<[[f32; 2]; 2]>,
    pub viewport_to_context_transform: Option<[f32; 9]>,
    /* private fields */
}

A rectangular region that directs injected events into a target.

The viewport relates a pointer’s position across multiple independent coordinate systems: the context, the viewport, and the dispatch clients. Intuitively, the viewport is how a pointer’s position is mapped to an interactive part of the scene.

A matrix is used to relate the viewport coordinate system to the context coordinate system. A pair of extents defines the viewport’s size in the viewport coordinate system. Together, they define the viewport’s placement in the context coordinate system.

The viewport coordinate system is used to convey a pointer’s coordinates in a scale-invariant way to dispatch clients, so that pointer movement can be interpreted correctly under effects like magnification. The context defines the viewport’s minimal and maximal extents in the viewport coordinate system.

• The boundary of the viewport, a rectangle, is axis aligned with the viewport coordinate system; however it may otherwise be freely positioned (“float”) within it: there is translation and scaling, but no rotation.
• Floating gives the injector some choice in how to convey coordinates, such as in Vulkan NDC, or in display pixel coordinates.
• The viewport rectangle defines a latch region used in dispatch (described below).

A dispatch client receives a pointer’s coordinates in the viewport coordinate system, along with a matrix to convert coordinates from the viewport coordinate system to the dispatch client’s coordinate system.

All fields required.

TODO(https://fxbug.dev/42162296): Rename Viewport, it is used in Flatland.

Fields

extents: Option<[[f32; 2]; 2]>

The viewport’s minimal and maximal extents in the viewport coordinate system.

viewport_to_context_transform: Option<[f32; 9]>

A transformation matrix that describes how to map the viewport coordinate system to the context coordinate system.

This transform, together with |extents|, defines the viewport’s placement in the context coordinate system.

This transform must be an invertible matrix (i.e., has a non-zero determinant), which guarantees it describes a bijection between the viewport coordinate system and the context coordinate system. A non-invertible matrix is rejected.

Trait Implementations

impl Clone for Viewport

fn clone(&self) -> Viewport

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Viewport

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

Formats the value using the given formatter.

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

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 Default for Viewport

fn default() -> Viewport

Returns the “default value” for a type.

impl<D: ResourceDialect> Encode<Viewport, D> for &Viewport

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 PartialEq for Viewport

fn eq(&self, other: &Viewport) -> 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 TypeMarker for Viewport

type Owned = Viewport

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 Viewport

type Borrowed<'a> = &'a Viewport

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 Persistable for Viewport

impl StructuralPartialEq for Viewport