Introduce methods to temporarily release the 48KB framebuffer during memory-intensive chapter builds, allowing the memory to be reused. Add font metadata query methods (hasGlyphMeta, ensureAdvance) that check glyph existence and fetch advance metrics without loading full bitmap data, avoiding expensive SD reads during layout measurement.
Replace fixed-size arena buffers with two-pass allocation strategy. First pass parses book into temporary full-size arena to determine actual memory footprint (5-40 KB vs 48 KB cap), then reallocates exact-sized buffers. This reduces peak memory usage by avoiding simultaneous allocation of all arenas with chapter-build scratch buffer (~100 KB) on constrained heap (~140 KB free). Stylesheet is also compacted to actual size, and all open-time transients are freed before per-chapter arenas are allocated.
Implements layout-independent bookmarks using character offsets within chapters instead of percentage-based positions. This allows bookmarks to restore to the exact position regardless of font size or orientation changes. Adds TOC navigation helpers, book progress calculation based on spine item sizes, and a NONE BidiBaseDir option for pre-reordered text. Legacy bookmarks without character offsets fall back to percentage-based positioning.
Justin Mitchell