Enum LayoutDecision 

pub enum LayoutDecision {
    #[non_exhaustive]
    PriorityDrop {
        id: Cow<'static, str>,
        priority: u8,
        terminal_width: u16,
        overflow: u32,
        dropped_width: u16,
    },
    #[non_exhaustive]
    ShrinkApplied {
        id: Cow<'static, str>,
        from: u16,
        to: u16,
        target: u16,
    },
    #[non_exhaustive]
    ReflowApplied {
        id: Cow<'static, str>,
        from: u16,
        to: u16,
        target: u16,
    },
    #[non_exhaustive]
    WidthBoundUnderMinDrop {
        id: Cow<'static, str>,
        rendered_width: u16,
        min: u16,
    },
    #[non_exhaustive]
    WidthBoundOverMaxTruncate {
        id: Cow<'static, str>,
        rendered_width: u16,
        max: u16,
    },
}

Event emitted by the layout engine when it takes one of five decisions under width pressure. The id field on every variant is borrowed from [crate::segments::LineItem::Segment.id] (per ADR-0026); built-in segment ids carry as Cow::Borrowed so the production path stays allocation-free.

Engine emit sites use the pub(crate) constructors below to pick up the debug_assert!’d width-relation invariants for free.

Variants

#[non_exhaustive]

PriorityDrop

The reflow loop dropped a segment outright (no shrink form via try_shrink, no truncatable end-ellipsis feasible via try_reflow, or simply not truncatable). Fires whenever the engine removes a segment under width pressure.

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

id: Cow<'static, str>

priority: u8

Engine defaults().priority at drop time. > 0 (priority-0 is pinned per highest_priority_droppable).

terminal_width: u16

Terminal cell budget at the call site (apply_layout’s terminal_width parameter).

overflow: u32

total_width() - budget at loop entry; >= 1. u32 mirrors total_width()’s overflow-safe accumulator so a layout with many wide segments can’t wrap u16.

dropped_width: u16

Pre-drop rendered.width of the segment removed (not the line delta). May be 0 — empty-render segments are valid drop targets when separator pressure forces slot removal.

#[non_exhaustive]

ShrinkApplied

try_shrink returned a valid compact render. from is the pre-shrink width, to is the post-shrink width, target is the width the reflow loop asked the segment to fit under. Invariant: to <= target < from.

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

id: Cow<'static, str>

from: u16

to: u16

target: u16

#[non_exhaustive]

ReflowApplied

try_reflow succeeded with an end-ellipsis on a truncatable segment. Same from/to/target shape as ShrinkApplied.

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

id: Cow<'static, str>

from: u16

to: u16

target: u16

#[non_exhaustive]

WidthBoundUnderMinDrop

apply_width_bounds returned None because the rendered width fell below the configured width.min — the segment is hidden rather than displayed at a wrong width.

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

id: Cow<'static, str>

rendered_width: u16

min: u16

#[non_exhaustive]

WidthBoundOverMaxTruncate

apply_width_bounds clipped a too-wide render via truncate_to (end-ellipsis) because rendered_width > max. Emitted at the apply_width_bounds call site, NOT inside truncate_to itself (which is also reached from try_reflow, where the emit is ReflowApplied).

Fields

Non-exhaustive enum variants could have additional fields added in future. Therefore, non-exhaustive enum variants cannot be constructed in external crates and cannot be matched against.

id: Cow<'static, str>

rendered_width: u16

max: u16

Implementations

impl LayoutDecision

pub fn remediation(&self) -> Option<&'static str>

Engine-recommended remediation phrasing for the decision, or None when the decision doesn’t have a user-actionable fix. Returns &'static str because every remediation is a literal; reach for format! and the signature stops compiling, which keeps the table in one place and testable.

Per-variant match (no _ arm) so a future sixth variant forces the author to declare its remediation intent at compile time rather than silently inheriting None.

Trait Implementations

impl Clone for LayoutDecision

fn clone(&self) -> LayoutDecision

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LayoutDecision

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

Formats the value using the given formatter.

impl PartialEq for LayoutDecision

fn eq(&self, other: &LayoutDecision) -> 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 Eq for LayoutDecision

impl StructuralPartialEq for LayoutDecision