Struct Ruler 

pub struct Ruler<'a> { /* private fields */ }

Converts between scales for one specific text.

A Ruler cannot be built without the text, which is the structural reason a scale conversion can never be done “in general”: there is no such thing. "héllo".len() is 6 bytes and 5 chars, and only the string knows.

Implementations

impl<'a> Ruler<'a>

pub const fn new(text: &'a str) -> Ruler<'a>

pub const fn end_bytes(&self) -> Offset<Bytes>

The text’s end, in bytes.

pub fn end_chars(&self) -> Offset<Chars>

The text’s end, in chars.

pub fn snap(&self, at: Offset<Bytes>) -> Offset<Bytes>

Clamp into the text and snap DOWN to a character boundary.

Snapping down, not up, keeps the result inside the character the offset pointed at — where an editor should underline. Mid-codepoint offsets are a NORMAL arrival, not corruption: they come from parser error spans over a buffer the user is halfway through typing a character into. Measured 2026-08-01: analyse("🔥🔥🔥") aborted on exactly this at offset 1.

pub fn to_chars(&self, at: Offset<Bytes>) -> Offset<Chars>

Bytes → chars. Total: out-of-range and mid-codepoint inputs snap first.

pub fn to_bytes(&self, at: Offset<Chars>) -> Offset<Bytes>

Chars → bytes. Total: past-the-end saturates to the text’s end.

pub fn to_utf16(&self, at: Offset<Bytes>) -> Offset<Utf16Units>

Bytes → UTF-16 code units, for LSP.

Separate from Self::to_chars because they differ, and the difference is invisible until a user types an emoji: 🔥 is ONE char and TWO UTF-16 units. Conflating them shifts every position after it.

Trait Implementations

impl<'a> Clone for Ruler<'a>

fn clone(&self) -> Ruler<'a>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a> Copy for Ruler<'a>

impl<'a> Debug for Ruler<'a>

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

Formats the value using the given formatter.