Struct Rgba8Readback 

pub struct Rgba8Readback { /* private fields */ }

A submitted texture readback whose buffer has not been mapped yet.

The handle owns its staging buffer, so it outlives the renderer borrow and can be moved into an asynchronous browser task. Any pack target returns to the texture pool after its copy submission, before buffer mapping finishes.

Implementations

impl Rgba8Readback

pub const fn size(&self) -> RenderSize

Returns the pixel dimensions the mapped result will contain.

pub const fn staging_bytes(&self) -> u64

Returns bytes retained by the GPU-visible staging buffer.

pub fn wait_ready(&self) -> Result<(), RenderError>

Blocks a native caller until this specific readback submission is mapped.

Other work may be submitted between creating and waiting on the handle; the stored submission index prevents this wait from draining the entire device queue.

Errors

Returns RenderError::TextureReadback when mapping or device polling fails.

pub fn wait(self) -> Result<Vec<u8>, RenderError>

Waits for this readback and packs its mapped rows into RGBA8 pixels.

Errors

Returns RenderError::TextureReadback when mapping, polling, or row packing fails.

pub fn map_async( &self, on_ready: impl FnOnce(Result<(), RenderError>) + Send + 'static, )

Requests buffer mapping and reports readiness exactly once.

The callback receives the failure when mapping was refused or was already requested, which a caller must treat as a failed frame rather than as empty pixels.

pub fn poll(&self)

Advances backends that need explicit polling to resolve a mapping.

Browser WebGPU resolves mapping on its own event loop and ignores this; wgpu-core backends need it to make progress without a blocking wait.

pub fn finish(self) -> Result<Vec<u8>, RenderError>

Packs the mapped rows into tightly packed premultiplied RGBA8.

Errors

Returns RenderError::TextureReadback when the buffer is not mapped, and RenderError::GpuWorkDropped when the GPU did not run the copy: the buffer holds no pixels of this readback, so it is not recycled, and the renderer refuses further work.

Trait Implementations

impl Debug for Rgba8Readback

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

Formats the value using the given formatter.