Enum EngineError 

pub enum EngineError {
    AtlasError,
    MissingTextureBinding,
    IntermediateTextureTooLarge,
    IntermediateTextureLimitReached,
    TargetTooLarge,
    InvalidTransform,
    InvalidGeometry,
    SchedulerEscalation {
        reason: String,
    },
    RetainedKeyMissing {
        key: u64,
    },
    TooManyBackdrops {
        recorded: usize,
        max: usize,
    },
    AlphaCapacity,
    PaintCapacity,
}

Engine render errors — returned on frame paths, never panicked.

Mirrors the reference sparse-strips renderer’s error cases plus engine-specific constraints. The engine always returns errors on invalid or oversized resources rather than panicking, per Frust’s frame-path invariant (E17).

Variants

AtlasError

MissingTextureBinding

IntermediateTextureTooLarge

IntermediateTextureLimitReached

TargetTooLarge

InvalidTransform

InvalidGeometry

A command’s own geometry — a rectangle’s extents, a corner radius, a path point, a stroke width, a dash length or phase — is non-finite.

Separate from InvalidTransform because the two name different halves of a frame’s input: a transform maps geometry onto the device grid, while this is the geometry itself, and a caller chasing a blank frame needs to know which of the two it recorded wrong. Both are refused by the same up-front walk, before any lowering runs.

SchedulerEscalation

A frame’s layer shape is outside what the engine’s scheduler serves.

reason names what was found — a layer graph needing a third live intermediate page at one pass, a chain deeper than the two-page ping-pong serves, a filter layer, a non-default blend mode — because the caller’s own log is where a frame that produced no pixels has to be explainable from.

Returned rather than panicked (E17), but it is not a route to a second renderer: the engine tier carries none, and which renderer draws a surface is settled when that surface is configured, not per frame. The caller decides what becomes of the frame, and skipping it is the only answer available — frust-render’s engine arm releases the acquired texture unpresented, counts the refusal and logs reason rate-limited, leaving whatever was presented last on the screen.

Fields

reason: String

What the scheduler found that it does not serve.

RetainedKeyMissing

A Command::DrawRetained named a retained page the engine cannot composite it from: the key is not resident (evicted, never recorded, or dropped with the store), or it is resident at a placement the draw cannot be served from — another linear transform or extent, or under a coverage-mask clip a composite cannot honour (see crate::cache::retained).

The frame is refused before anything is recorded, exactly like every other variant here, and the retained store is cleared on the way out: the resident-key ledger the widget tree painted against was wrong, and the cheapest way back to an agreeing pair is an empty store whose empty ledger makes the next frame paint every body again. Logged once per refusal by the caller, like any refused frame.

Fields

key: u64

The raw key the DrawRetained carried.

TooManyBackdrops

A frame records more Command::BackdropBlurs than the engine serves in one frame (MAX_BACKDROPS_PER_FRAME).

Each backdrop costs the frame a cut of its surface pass, a region copy and a blur’s whole pass sequence, so the count is bounded rather than left to grow with a widget tree; a frame past the bound is refused up front, before anything is recorded, exactly like a scheduler escalation — never rendered with some of its backdrops missing.

Fields

recorded: usize

How many backdrop blurs the frame recorded.

max: usize

The per-frame bound.

AlphaCapacity

PaintCapacity

Trait Implementations

impl Clone for EngineError

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for EngineError

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

Formats the value using the given formatter.

impl Display for EngineError

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

Formats the value using the given formatter.

impl Error for EngineError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.