Function glyph_clusters 

pub fn glyph_clusters(
    glyphs: &[ShapedGlyph],
    text_len: usize,
) -> impl FusedIterator<Item = GlyphCluster<'_>>

Iterate over a left-to-right shaped glyph stream without allocating or copying glyphs.

Consecutive glyphs with equal cluster offsets form one group. Offsets must be nondecreasing UTF-8 byte boundaries in the text used for shaping; text_len must be that text’s byte length. For shape_with_fallback, use each WordSubRun’s normalized text and local glyph stream separately.

This function only groups glyphs: it does not normalize text, validate byte ranges, rebase offsets, or infer grapheme or line-break boundaries. Callers accepting externally constructed glyph streams should use str::get to validate each returned range before slicing. Descending RTL clusters are not supported. Empty glyph streams yield no clusters, including Base-14 runs.

use mos_fonts::{EmbeddedFontId, glyph_clusters, shape};

let text = "office";
let glyphs = shape(EmbeddedFontId::Regular.data(), text);
let parts: Vec<_> = glyph_clusters(&glyphs, text.len())
    .filter_map(|cluster| text.get(cluster.byte_range))
    .collect();
assert_eq!(parts.concat(), text);