frust-engine 0.5.2

Sparse-strip GPU render pipeline for Frust: compiles a scene display list into strips and records the draw passes on wgpu.
Documentation 
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use thiserror::Error;

/// 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).
#[derive(Debug, Clone, Error)]
pub enum EngineError {
    #[error("atlas allocation failed")]
    AtlasError,

    #[error("missing texture binding")]
    MissingTextureBinding,

    #[error("intermediate texture too large")]
    IntermediateTextureTooLarge,

    #[error("intermediate texture limit reached")]
    IntermediateTextureLimitReached,

    #[error("target exceeds u16 ceiling (65,535 pixels)")]
    TargetTooLarge,

    #[error("non-finite transform refused")]
    InvalidTransform,

    /// 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`](Self::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.
    #[error("non-finite geometry refused")]
    InvalidGeometry,

    /// 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.
    #[error("scheduler escalation: {reason}")]
    SchedulerEscalation {
        /// What the scheduler found that it does not serve.
        reason: String,
    },

    #[error("alpha capacity exhausted")]
    AlphaCapacity,

    #[error("encoded-paint capacity exhausted")]
    PaintCapacity,
}