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Producer

otf_pixels_core

Trait Producer 

Source 
pub trait Producer:
    Send
    + Sync
    + Debug {
    // Required methods
    fn name(&self) -> &'static str;
    fn descriptor(&self) -> ImageDescriptor;
    fn produce(&self, region: Region, output: &mut TileMut<'_>) -> Result<()>;

    // Provided methods
    fn capability(&self) -> DecodeCapability { ... }
    fn reduced_descriptor(&self, target: (u32, u32)) -> Option<ImageDescriptor> { ... }
    fn reduce_to(&self, descriptor: ImageDescriptor) -> Result<()> { ... }
}
Expand description

A source of pixels at the root of a graph.

Producers sit where decoders meet the graph. produce takes &self because graph nodes are shared across threads; a producer wrapping a single-pass streaming decoder therefore owns whatever interior mutability it needs (see DecodedSource).

Required Methods§

Source

fn name(&self) -> &'static str

A short, stable name for this producer, used in diagnostics.

Source

fn descriptor(&self) -> ImageDescriptor

The shape of the image this producer yields.

Known from the header alone; answering this must not decode pixels.

Source

fn produce(&self, region: Region, output: &mut TileMut<'_>) -> Result<()>

Fill output with the pixels of region.

region is always within descriptor().region().

§Errors

Returns PixelsError::Malformed on invalid input bytes, PixelsError::Io on source failure, or PixelsError::InvalidArgument if output does not cover region.

Provided Methods§

Source

fn capability(&self) -> DecodeCapability

Whether this producer can serve arbitrary regions, or only forward ones.

This is the upstream half of ADR-0009’s seam analysis: a producer that can only go forward forces the scheduler to materialize whenever demand is not forward-monotonic, while one serving arbitrary regions lets the same pipeline stream.

Defaults to DecodeCapability::Sequential, the conservative answer — over-declaring it costs a buffer, under-declaring it is a correctness bug.

Source

fn reduced_descriptor(&self, target: (u32, u32)) -> Option<ImageDescriptor>

What this producer would emit if asked for target or larger, when it can reach that size more cheaply than by producing full resolution.

Pure: nothing is committed, and calling this must not change what the producer subsequently emits. The planner asks first, checks the whole graph still holds, and only then calls Producer::reduce_to — so a producer that reduced itself here would corrupt pipelines the planner went on to reject.

The returned descriptor is never smaller than target in either axis: decoding below the requested size and enlarging afterwards would discard detail and then invent it back.

None — the default — means this producer has only one resolution.

Source

fn reduce_to(&self, descriptor: ImageDescriptor) -> Result<()>

Commit to emitting descriptor, which Producer::reduced_descriptor must have returned.

§Errors

Returns PixelsError::Unsupported if this producer cannot reduce, or PixelsError::InvalidArgument if pixels have already been produced — the resolution is fixed from the first Producer::produce onward, because rows already emitted cannot be retracted.

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§