Progress submissions now carry (percentage, context_text, epubcfi) and
the server becomes the position authority:
- VerifyProgressAnchor resolves the submitted standard CFI against the
book's own XHTML, extracts the text at the anchor, and cross-checks it
with the submitted context_text. A mismatch heals the anchor by text
search (percentage disambiguates repeats) instead of storing a bad
position.
- The anchor's block element is derived as a cssSelector plus a block-
relative character offset, and served on progress GET alongside the
anchor document's href — readium-native handles that let clients
re-open a book without parsing CFIs themselves.
- context_text-only submissions (no CFI — the dumb-client tier) are
anchored structurally from the context text.
Motivation: cross-client progress sync (web foliate CFIs, KOReader CRE
xpointers, readium-native apps) previously trusted each client's own
locator math; the app's EPUB restore drifted ±pages because readium's
paginator does not lay out far-from-viewport columns and the foliate-
ported CFI walk ran against readium's mutated WebView DOM. Server-side
verification heals both classes at ingest.
John O'Keefe
aec226af1a