Struct FormatCostKey

pub struct FormatCostKey {
    pub pixel_format: Option<PixelFormat>,
    pub pixel_format_modifier: Option<PixelFormatModifier>,
    pub buffer_usage_bits: Option<BufferUsage>,
    /* private fields */
}

Entries which have the same pixel_format, pixel_format_modifier, and required_usage_bits as a previous entry will override that previous entry. For matching purposes, an absent pixel_format_modifier matches LINEAR, and an absent required_buffer_usage_bits matches all-0 usage bits.

Fields

pixel_format: Option<PixelFormat>

The pixel_format and pixel_format_modifier are the format to which this FormatCost entry applies.

Must be set.

pixel_format_modifier: Option<PixelFormatModifier>

The pixel_format and pixel_format_modifier are the format to which this FormatCost entry applies.

Un-set is equivalent to LINEAR.

buffer_usage_bits: Option<BufferUsage>

If set, this entry is only considered if the buffer collection has at least these usage bits set.

The buffer collection has an aggregated BufferUsage which is the union of per-participant BufferUsage bits. FormatCost entries with additional set bits are ignored. Among the rest, the one with matching format and the most usage bits set determines the cost of that format for that buffer collection.

Then the lowest-cost format is chosen for that buffer collection among the formats that are mutually suppored by all the participants of that buffer collection.

The main intent of this field is to allow “waving off” a format that works, but doesn’t perform well, for a particular combination of usages. In that case the cost can be set high when the problematic combination of usage bits is set. The format will still be chosen if this format is the only mutually-supported format among the participants of the buffer collection.

Un-set is equivalent to zero usage bits set, meaning the entry applies to the format unless another entry with more specific usage applies.

It can be reasonable in some cases for all entries to omit this field, when/if format selection based on format cost alone, ignoring usage, is sufficient.

Trait Implementations

impl Clone for FormatCostKey

fn clone(&self) -> FormatCostKey

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for FormatCostKey

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

Formats the value using the given formatter.

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

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 FormatCostKey

fn default() -> FormatCostKey

Returns the “default value” for a type.

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

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 FormatCostKey

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

type Owned = FormatCostKey

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 FormatCostKey

type Borrowed<'a> = &'a FormatCostKey

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 FormatCostKey

impl StructuralPartialEq for FormatCostKey