[JimmyJi0309]

Summary

Fix two independent EPUB-reader problems reported on a phone:

1. A full-width illustration was split across two pages, with a narrow image strip or 1px vertical line left at the page edge.
2. Changing typography caused a temporary layout error until the book was closed and reopened.

The tablet rendering was unaffected.

Cause

Illustration split

A reflowable EPUB with a large inline illustration (roughly 1026 × 1465, plain <p><img> with no publisher CSS, float, or fixed dimensions) exposed the issue. On the narrower phone page, the image was laid out wider than one rendered page/column and Readium split it across pages. The first normalizer attempt also ran before the WebView had a measurable width and could compute a 1px image width, producing a stray vertical edge line.

Typography layout

Readium applies typography through a live submitPreferences CSS reflow, but its pagination is index-based. After a large reflow it keeps the old page index instead of re-anchoring the locator, so the visible page is temporarily wrong. Reopening recreates the navigator and paginates once from the saved locator, which is why close/reopen fixed it.

A separate EPUB defect was also fixed: unlike the PDF and comic readers, the EPUB reader did not reserve space for the optional title/author header, so the header could overlay content.

Changes

• Add epubLayoutChangeRequiresRelayout(...) covering font size/family, spacing, alignment, hyphenation, page padding, header visibility, progress-footer visibility and layout mode. Reading-direction-only changes are excluded because EPUB reading progression is fixed to LTR.
• When such a change is made from the reader options sheet, mark a relayout pending. On closing the sheet, recreate the reader once so Readium applies the final pagination from its restored locator instead of keeping the stale live offset.
• Keep the pending relayout from recreating while chrome is being shown; only an actual options-sheet close triggers the one-pass reopen.
• Reserve the header top padding in the EPUB applyReaderPadding() path using the same readerHeaderReservedTopSpace(...) helper as PDF/comic, and re-apply padding after header/inset changes.
• Add a large-media normalizer to each EPUB document: images/SVGs larger than 512px are capped to one rendered page/column width and height, centered, and re-run on load/resize. Small inline icons are left alone.
• Wait for a measurable WebView width and leave an 8px edge gap before normalizing, preventing a 1px image edge from becoming a vertical line at the page margin.
• Add a JVM regression test for the relayout predicate.

Verification

• Real phone Huawei ELS-AN00, debug build: illustration no longer splits across pages; the 1px edge line is gone; typography layout stays correct after changing settings and closing the options sheet.
• API 35 phone emulator: the same structure renders with the illustration on one page in portrait and landscape.
• Tested locally with a reflowable EPUB containing a large inline <p><img> (about 1026×1465) and no image CSS; the fixture is not attached to keep the PR small.
• JVM: 1,335 tests, 0 failures
• lint: 0 errors
• ./gradlew testDebugUnitTest lintDebug assembleDebug assembleDebugAndroidTest — passed
• No changes to Readium's publisherStyles, shouldApplyInsetsPadding, or the legacy WebView reader path.

Notes

The EPUB fixes are independent of the reader-settings feature branch. The typography fix intentionally recreates once when the options sheet is closed; changing typography and continuing to read with the sheet open may still show the live reflow until the sheet is dismissed.

Close #401

[RobinD42]

The layout reflow issue was on my list too. 😄