Enum ReplaceFormatPolicy 

pub enum ReplaceFormatPolicy {
    InheritPreceding,
    PreserveIfFullyCovered,
    KeepDominantRun,
    PreserveNothing,
}

What the replacement text wears when it overwrites formatted text.

Before this existed the behaviour was emergent, not chosen: a replace was a delete followed by an insert, and shift_runs_for_insert hardcodes “the inserted text inherits whatever run ends at the insertion point”. That silently destroys formatting — renaming a character whose name reads Auré**lien** dropped the bold entirely, and not one test in the repo covered it.

The old behaviour is still the default (and is byte-for-byte identical); it is now simply one option among four, and the caller has to look at it.

Variants

InheritPreceding

The replacement inherits the format of the run that straddles the start of the replaced range or ends exactly on it (precisely: byte_start < start && byte_end >= start); otherwise it is unformatted. A run beginning exactly at the start never contributes.

This is the Qt / ProseMirror insertion convention, and it is what delete-then-insert has always produced — byte for byte, which inherit_preceding_matches_the_historical_delete_then_insert pins differentially (it runs the historical primitives and compares, rather than trusting a transcription of them).

PreserveIfFullyCovered

If a single run covers the whole replaced range, the replacement keeps that run’s format; otherwise fall back to Self::InheritPreceding. “Rename a name that was entirely bold and it stays bold” — without guessing when the range is formatted unevenly.

KeepDominantRun

The replacement takes the format that covered the most bytes of the replaced range. Unformatted gaps count as a candidate, so a mostly-plain range stays plain; ties go to the formatted run, because a tie means the writer’s formatting covered at least as much as its absence and dropping it is the destructive answer.

PreserveNothing

The replacement carries no formatting at all.

Trait Implementations

impl Clone for ReplaceFormatPolicy

fn clone(&self) -> ReplaceFormatPolicy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ReplaceFormatPolicy

impl Debug for ReplaceFormatPolicy

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

Formats the value using the given formatter.

impl Default for ReplaceFormatPolicy

fn default() -> ReplaceFormatPolicy

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for ReplaceFormatPolicy

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for ReplaceFormatPolicy

impl PartialEq for ReplaceFormatPolicy

fn eq(&self, other: &ReplaceFormatPolicy) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for ReplaceFormatPolicy

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ReplaceFormatPolicy