The debug aid confirmed peer presence arrives with real selections
(sel=Some { anchor: 1837, active: 1844 }), yet no wash drew — because
the rect geometry was computed against the wrong coordinate space.
cosmic-text's `LayoutGlyph::{start,end}` are byte offsets within the
*original line* (`LayoutRun::line_i`), not the whole buffer.
`push_glyph_extent_rects` was comparing those line-relative offsets
against whole-buffer byte ranges from presence/`source_line_range`.
They only coincide on line 0, so any Selection or CurrentLine past the
first line never matched a glyph and produced no rect — "blind." This
was latent since 9.1 (Selection was never visually validated) and was
masked in 9.2 whenever the cursor happened to sit on line 0.
Fix: build `line_byte_offsets(current_text)` — the buffer-absolute
start of each `\n`-delimited line — and rebase each run's glyphs by
`line_offsets[run.line_i]` before comparing. Computed once per
`peer_background_rects` call and threaded into
`push_glyph_extent_rects`.
New test `line_byte_offsets_indexes_each_logical_line`.
Gates: fmt clean; clippy -p pmacs-gpu -D warnings clean; pmacs-gpu
unit 16 (+1).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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