Huang Xin 789d031222 feat(reader): line-aware reading ruler (#4358) ...

Snap the reading ruler to real rendered text lines instead of stepping by a
fixed arithmetic height, so the band always frames whole lines.

- Snap to actual line geometry from the relocate range; the band is sized
  dynamically to the text block plus symmetric padding (round(fontSize *
  lineHeight * 0.3)), capped at (lines + 1) line heights so a tall image inside
  a block can't expand it to cover the whole figure.
- Drop block/container rects (Range.getClientRects aggregates multi-line element
  borders) so paragraphs aren't merged into one giant line and skipped.
- Column-aware in multi-column layouts: the band spans one column at a time and
  advances column by column.
- Confine the band to lines at least half visible within the viewport.
- Scrolled mode: snap to lines, and at a view edge scroll the view and realign
  the band to the start/end of the new view (works for vertical-rl too, which
  scrolls horizontally); paging snaps the view edge between lines so text isn't
  cut or repeated.
- Vertical writing mode: correct band centering and drag direction; Up/Down keys
  move the ruler while Left/Right turn pages (taps always move the ruler).
- Page turns keep the first/last line: forward lands on the first line of the new
  page, backward on the last line; the relayout re-snap anchors on the band's
  leading edge so it never skips a line.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-05-29 19:16:53 +02:00

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2026-05-29-line-aware-reading-ruler.md

feat(reader): line-aware reading ruler (#4358)

2026-05-29 19:16:53 +02:00