Struct FormatCostEntry 

pub struct FormatCostEntry {
    pub key: Option<FormatCostKey>,
    pub cost: Option<f32>,
}

A FormatCostEntry can be used to influence which PixelFormatAndModifier is chosen for a buffer collection, optionally taking BufferUsage into account.

The default cost is f32::MAX, so any specified cost with a non-MAX value will prefer the specified format over any formats that don’t have any FormatCost entry.

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.

Board info sysmem_defaults entries are logically before platform sysmem entries.

Sysmem uses the resulting aggregated list of FormatCostEntry(s) when breaking ties among the set of formats which are supported by all participants of a buffer collection. For each mutually-supported format, entries with non-matching format are ignored, and entries with extra buffer_usage_bits set are ignored. Among the remaining entries, the entry with the most usage bits in common with the aggregated participant usages is selected to determine the cost (if a tie, the later entry wins). Then the format with the lowest cost is chosen. If it’s still a tie (equal cost), the tie is broken arbitrarily but not randomly.

This is not intended as a mechanism to disallow selection of a format that is supported by all participants of a buffer collection. If a participant claims support for a format but fails to handle that format correctly, it should be fixed to handle that format correctly or changed to stop claiming support for that format.

This mechanism is intended to influence format selection toward more efficient formats with better performance, lower memory bandwidth usage, etc, for a given set of usage bits, taking into account quirks that may be unique to a given board or overall platform config.

Fields

key: Option<FormatCostKey>

cost: Option<f32>

Trait Implementations

impl Clone for FormatCostEntry

fn clone(&self) -> FormatCostEntry

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FormatCostEntry

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

Formats the value using the given formatter.

impl Default for FormatCostEntry

fn default() -> FormatCostEntry

Returns the “default value” for a type.

impl<'a, ___E> Encode<FormatCostEntry<'static>, ___E> for &'a FormatCostEntry

where ___E: Encoder + ?Sized,

fn encode( self, encoder: &mut ___E, out: &mut MaybeUninit<FormatCostEntry<'static>>, _: (), ) -> Result<(), EncodeError>

Encodes this value into an encoder and output.

const COPY_OPTIMIZATION: CopyOptimization<Self, W> = _

Whether the conversion from Self to W is equivalent to copying the raw bytes of Self.

impl<___E> Encode<FormatCostEntry<'static>, ___E> for FormatCostEntry

where ___E: Encoder + ?Sized,

fn encode( self, encoder: &mut ___E, out: &mut MaybeUninit<FormatCostEntry<'static>>, _: (), ) -> Result<(), EncodeError>

Encodes this value into an encoder and output.

const COPY_OPTIMIZATION: CopyOptimization<Self, W> = _

Whether the conversion from Self to W is equivalent to copying the raw bytes of Self.

impl<'de> FromWire<FormatCostEntry<'de>> for FormatCostEntry

fn from_wire(wire_: FormatCostEntry<'de>) -> FormatCostEntry

Converts the given owned value to this type.

const COPY_OPTIMIZATION: CopyOptimization<W, Self> = _

Whether the conversion from W to Self is equivalent to copying the raw bytes of W.

impl<'de> FromWireRef<FormatCostEntry<'de>> for FormatCostEntry

fn from_wire_ref(wire: &FormatCostEntry<'de>) -> FormatCostEntry

Converts the given reference to this type.

impl PartialEq for FormatCostEntry

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

fn partial_cmp(&self, other: &FormatCostEntry) -> 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 Copy for FormatCostEntry

impl StructuralPartialEq for FormatCostEntry