Add anti-aliasing mode translations (Full/Fast)

Add STR_TEXT_AA_FULL and STR_TEXT_AA_FAST translation strings across all supported languages. Also includes a complete retranslation of the Slovak language file.

.gitmodules

@@ -1,3 +1,4 @@
-[submodule "open-x4-sdk"]
-	path = open-x4-sdk
-	url = https://github.com/crosspoint-reader/community-sdk.git
+[submodule "freeink-sdk"]
+	path = freeink-sdk
+	url = https://github.com/Free-Ink/freeink-sdk.git
+	branch = main

.skills/SKILL.md

@@ -7,7 +7,7 @@ Mission: Provide a lightweight, high-performance reading experience focused on E
 * Role: Senior Embedded Systems Engineer (ESP-IDF/Arduino-ESP32 specialized).
 * Primary Constraint: 380KB RAM is the hard ceiling. Stability is non-negotiable.
 * Evidence-Based Reasoning: Before proposing a change, you MUST cite the specific file path and line numbers that justify the modification.
-* Anti-Hallucination: Do not assume the existence of libraries or ESP-IDF functions. If you are unsure of an API's availability for the ESP32-C3 RISC-V target, check the open-x4-sdk or official docs first.
+* Anti-Hallucination: Do not assume the existence of libraries or ESP-IDF functions. If you are unsure of an API's availability for the ESP32-C3 RISC-V target, check the freeink-sdk source or the FreeInk SDK docs (https://freeink.org/llms.txt for an LLM-readable index) first.
 * No Unfounded Claims: Do not claim performance gains or memory savings without explaining the technical mechanism (e.g., DRAM vs IRAM usage).
 * Resource Justification: You must justify any new heap allocation (new, malloc, std::vector) or explain why a stack/static alternative was rejected.
 * Verification: After suggesting a fix, instruct the user on how to verify it (e.g., monitoring heap via Serial or checking a specific cache file).
@@ -127,7 +127,7 @@ These flags in `platformio.ini` fundamentally affect firmware behavior:
   * lib/hal/: Hardware Abstraction Layer (HalDisplay, HalGPIO, HalStorage)
   * lib/I18n/: Internationalization (translations in `translations/*.yaml`, generated string tables)
 * src/activities/: UI logic using the Activity Lifecycle (onEnter, loop, onExit)
-* open-x4-sdk/: Low-level SDK (EInkDisplay, InputManager, BatteryMonitor, SDCardManager)
+* freeink-sdk/: Low-level SDK (EInkDisplay, InputManager, BatteryMonitor, SDCardManager)
 * .crosspoint/: SD-based binary cache for EPUB metadata and pre-rendered layout sections
 
 ### Hardware Abstraction Layer (HAL)

README.md

@@ -67,10 +67,6 @@ USB port or browser before assuming the device is locked. Only reach for the unl
 > Flashing any other firmware on a USB-locked device may **permanently brick the device** or leave it **permanently
 > stuck on that firmware with no recovery path**. Once USB flashing is re-locked, your only way back is via OTA, and if
 > the firmware you flashed doesn't support OTA, **there is no way out**.
-> 
-> **The Papyrix fork has removed OTA update support from its code.** If you flash Papyrix onto a
-> USB-locked unit, you will have **zero update or recovery path** and will be stuck on it forever. **Do not flash
-> Papyrix (or any other unsupported firmware) on a locked device.**
 
 ## Install firmware
 
@@ -249,7 +245,7 @@ One of the best things about open source is that anyone can take the code in a d
 
 - [papyrix-reader](https://github.com/bigbag/papyrix-reader) — Adds FB2 and MD format support. Actively maintained with Arabic script support. Custom themes via SD card.
 
-- [crosspet](https://github.com/trilwu/crosspet) — A Vietnamese fork that adds a Tamagotchi-style virtual chicken that grows based on your reading milestones (pages read, streaks, care). Also: Flashcards, Weather, Pomodoro timer, and mini-games.
+- ~~[crosspet](https://github.com/trilwu/crosspet) — A Vietnamese fork that adds a Tamagotchi-style virtual chicken that grows based on your reading milestones (pages read, streaks, care). Also: Flashcards, Weather, Pomodoro timer, and mini-games.~~ (Unmaintained)
 
 - [crosspoint-reader-cjk](https://github.com/aBER0724/crosspoint-reader-cjk) — Purpose-built for Chinese, Japanese, and Korean reading.
 

USER_GUIDE.md

@@ -5,6 +5,7 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
 - [CrossPoint User Guide](#crosspoint-user-guide)
   - [1. Hardware Overview](#1-hardware-overview)
     - [Button Layout](#button-layout)
+    - [Taking a Screenshot](#taking-a-screenshot)
   - [2. Power \& Startup](#2-power--startup)
     - [Power On / Off](#power-on--off)
     - [First Launch](#first-launch)
@@ -14,7 +15,11 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
     - [3.3 Browse Files Screen](#33-browse-files-screen)
     - [3.4 Recent Books Screen](#34-recent-books-screen)
     - [3.5 File Transfer Screen](#35-file-transfer-screen)
-      - [3.5.1 Calibre Wireless Transfers](#351-calibre-wireless-transfers)
+    - [3.5.1 Calibre Wireless Transfers](#351-calibre-wireless-transfers)
+      - [Installing the Plugin in Calibre](#installing-the-plugin-in-calibre)
+      - [Configuring the CrossPoint Plugin in Calibre](#configuring-the-crosspoint-plugin-in-calibre)
+      - [Uploading Books](#uploading-books)
+      - [Removing a Book](#removing-a-book)
     - [3.6 Settings](#36-settings)
       - [3.6.1 Display](#361-display)
       - [3.6.2 Reader](#362-reader)
@@ -23,21 +28,25 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
       - [3.6.5 OPDS Servers (Multiple Libraries)](#365-opds-servers-multiple-libraries)
       - [3.6.6 Web Settings (Wi-Fi + OPDS)](#366-web-settings-wi-fi--opds)
       - [3.6.7 KOReader Sync Quick Setup](#367-koreader-sync-quick-setup)
+        - [Option A: Free Public Server (`sync.koreader.rocks`)](#option-a-free-public-server-synckoreaderrocks)
+        - [Option B: Self-Hosted Server (Docker Compose)](#option-b-self-hosted-server-docker-compose)
     - [3.7 Sleep Screen](#37-sleep-screen)
+      - [Cover settings](#cover-settings)
+      - [Custom images](#custom-images)
     - [3.8 Custom Fonts (SD Card)](#38-custom-fonts-sd-card)
   - [4. Reading Mode](#4-reading-mode)
-      - [Page Turning](#page-turning)
-      - [Chapter Navigation](#chapter-navigation)
-      - [Auto Page Turn](#auto-page-turn)
-      - [Tilt Page Turn (X3 only)](#tilt-page-turn-x3-only)
-      - [Footnote Navigation](#footnote-navigation)
-      - [System Navigation](#system-navigation)
-      - [Supported Languages](#supported-languages)
+    - [Page Turning](#page-turning)
+    - [Chapter Navigation](#chapter-navigation)
+    - [Auto Page Turn](#auto-page-turn)
+    - [Tilt Page Turn (X3 only)](#tilt-page-turn-x3-only)
+    - [Footnote Navigation](#footnote-navigation)
+    - [System Navigation](#system-navigation)
+    - [Supported Languages](#supported-languages)
   - [5. Reader Menu](#5-reader-menu)
-      - [5.1 Chapter Selection](#51-chapter-selection)
-      - [5.2 Bookmarks](#52-bookmarks)
-  - [6. Current Limitations & Roadmap](#6-current-limitations--roadmap)
-  - [7. Troubleshooting Issues & Escaping Bootloop](#7-troubleshooting-issues--escaping-bootloop)
+    - [5.1 Chapter Selection](#51-chapter-selection)
+    - [5.2 Bookmarks](#52-bookmarks)
+  - [6. Current Limitations \& Roadmap](#6-current-limitations--roadmap)
+  - [7. Troubleshooting Issues \& Escaping Bootloop](#7-troubleshooting-issues--escaping-bootloop)
 
 ## 1. Hardware Overview
 
@@ -174,6 +183,7 @@ The Settings screen allows you to configure the device's behavior. There are a f
   - "Cover" - The book cover image (Note: this is experimental and may not work as expected)
   - "None" - A blank screen
   - "Cover + Custom" - The book cover image while actively reading, falls back to "Custom" behavior otherwise
+  - "Quick resume" - The text of the last page read will be displayed on the sleep screen and a moon icon is shown on the edge of the screen. Waking up the device will return to the same page of the opened book. This is useful for quickly resuming reading without waiting for the device to fully wake up and load the book.
 
 - **Sleep Screen Cover Mode**: How to display the book cover when "Cover" sleep screen is selected:
   
@@ -186,6 +196,8 @@ The Settings screen allows you to configure the device's behavior. There are a f
   - "Contrast" - The image will be displayed as a black & white image without grayscale conversion
   - "Inverted" - The image will be inverted as in white & black and will be displayed without grayscale conversion
 
+- **Quick Resume on Timeout**: Whether to enable the "Quick Resume" sleep screen when the device goes to sleep due to inactivity (System > Time to Sleep). This is useful for quickly resuming reading without waiting for the device to fully wake up and load the book. This overwrites the Sleep Screen Cover Mode when enabled.
+
 - **Status Bar**: Configure the status bar displayed while reading:
   
   - "None" - No status bar

bin/clang-format-fix.ps1

@@ -4,7 +4,7 @@
 
 .DESCRIPTION
     Formats all C/C++ source and header files in the repository, excluding
-    generated, vendored, and build directories (open-x4-sdk, builtinFonts,
+    generated, vendored, and build directories (freeink-sdk, builtinFonts,
     hyphenation tries, uzlib, .pio, *.generated.h).
 
     The clang-format binary path is resolved once and cached in
@@ -92,7 +92,7 @@ function Resolve-ClangFormat {
 $clangFormat = Resolve-ClangFormat
 
 $exclude = @(
-    'open-x4-sdk'
+    'freeink-sdk'
     'lib\EpdFont\builtinFonts'
     'lib\Epub\Epub\hyphenation\generated'
     'lib\uzlib'

docs/contributing/architecture.md

@@ -8,7 +8,7 @@ At a high level, it is firmware that uses an activity-driven application archite
 
 ```mermaid
 graph TD
-    A[Hardware: ESP32-C3 + SD + E-ink + Buttons] --> B[open-x4-sdk]
+    A[Hardware: ESP32-C3 + SD + E-ink + Buttons] --> B[freeink-sdk]
     B --> C[lib/hal wrappers]
     C --> D[src/main.cpp runtime loop]
     D --> E[Activities layer]
@@ -195,10 +195,10 @@ When editing related source assets, regenerate via normal build steps/scripts.
 - `src/`: app orchestration, settings/state, and activity implementations
 - `src/network/`: web server and OTA/update networking
 - `src/components/`: theming and shared UI components
-- `lib/hal/`: hardware abstraction wrappers around open-x4-sdk
+- `lib/hal/`: hardware abstraction wrappers around freeink-sdk
 - `lib/Epub/`: EPUB parser, layout, CSS handling, and hyphenation
 - `lib/`: supporting libraries (fonts, text, filesystem helpers, etc.)
-- `open-x4-sdk/`: hardware SDK submodule (display, input, storage, battery)
+- `freeink-sdk/`: hardware SDK submodule (display, input, storage, battery). Docs: https://freeink.org/docs
 - `docs/`: user and technical documentation
 
 ## Embedded constraints that shape design

docs/file-formats.md

@@ -90,13 +90,13 @@ if (parsedSize != fileSize) {
 
 ## `section.bin`
 
-### Version 25
+### Version 28
 
 Each file in `sections/*.bin` stores one laid-out spine section. The header is
 also the cache-busting key: if any layout-affecting setting differs from the
 current reader settings, the section is discarded and rebuilt.
 
-Version 25 includes:
+Version 28 includes:
 
 - cache-busting fields for paragraph alignment, hyphenation, embedded CSS,
   image rendering mode, and Focus Reading
@@ -105,6 +105,8 @@ Version 25 includes:
 - paragraph and list-item LUTs used by KOReader sync page refinement
 - optional per-word Focus Reading split metadata
 - per-page footnote entries
+- serialized word style bits for underline, strikethrough, superscript, and
+  subscript
 
 ImHex pattern:
 
@@ -113,7 +115,7 @@ import std.mem;
 import std.string;
 import std.core;
 
-#define EXPECTED_VERSION 25
+#define EXPECTED_VERSION 28
 #define MAX_STRING_LENGTH 65535
 #define FOOTNOTE_NUMBER_LEN 32
 #define FOOTNOTE_HREF_LEN 96

lib/EpdFont/EpdFontFamily.cpp

@@ -1,7 +1,7 @@
 #include "EpdFontFamily.h"
 
 const EpdFont* EpdFontFamily::getFont(const Style style) const {
-  // Extract font style bits (ignore UNDERLINE bit for font selection)
+  // Extract font style bits; render-time overlay bits do not affect font selection.
   const bool hasBold = (style & BOLD) != 0;
   const bool hasItalic = (style & ITALIC) != 0;
 

lib/EpdFont/EpdFontFamily.h

@@ -17,6 +17,7 @@ class EpdFontFamily {
     SUP = 16,           // superscript: glyph scaled 50%, raised ~40% of ascender
     SUB = 32,           // subscript: glyph scaled 50%, lowered ~25% of ascender
   };
+  static constexpr uint8_t TEXT_DECORATION_MASK = static_cast<uint8_t>(UNDERLINE | STRIKETHROUGH);
 
   explicit EpdFontFamily(const EpdFont* regular, const EpdFont* bold = nullptr, const EpdFont* italic = nullptr,
                          const EpdFont* boldItalic = nullptr)
@@ -27,6 +28,9 @@ class EpdFontFamily {
   const EpdGlyph* getGlyph(uint32_t cp, Style style = REGULAR) const;
   int8_t getKerning(uint32_t leftCp, uint32_t rightCp, Style style = REGULAR) const;
   uint32_t applyLigatures(uint32_t cp, const char*& text, Style style = REGULAR) const;
+  static constexpr bool hasTextDecoration(const Style style) {
+    return (static_cast<uint8_t>(style) & TEXT_DECORATION_MASK) != 0;
+  }
 
  private:
   const EpdFont* regular;

lib/EpdFont/scripts/build-sd-fonts.py

@@ -33,6 +33,7 @@ import sys
 import tempfile
 import threading
 import time
+import socket
 import urllib.request
 from concurrent.futures import ProcessPoolExecutor, as_completed
 from pathlib import Path
@@ -49,17 +50,44 @@ INSTANCE_DIR = SCRIPT_DIR / "instanced_fonts"
 DEFAULT_FALLBACK_FONT = EPDFONTS_DIR / "builtinFonts/source/NotoSans/NotoSans-Regular.ttf"
 
 
-def download_font(url: str, dest: Path) -> Path:
-    """Download a font file if not already cached. Returns the local path."""
+_orig_getaddrinfo = socket.getaddrinfo
+
+
+def _ipv4_only_getaddrinfo(*args, **kwargs):
+    """getaddrinfo variant that drops AAAA records (IPv4 only)."""
+    return [ai for ai in _orig_getaddrinfo(*args, **kwargs) if ai[0] == socket.AF_INET]
+
+
+def download_font(url: str, dest: Path, retries: int = 3) -> Path:
+    """Download a font file if not already cached. Returns the local path.
+
+    Some sources (e.g. mirrors.ctan.org) are round-robin redirectors that land
+    on a different mirror each request; a mirror may advertise an IPv6 address a
+    host without an IPv6 route cannot reach ([Errno 101] Network is unreachable).
+    Retry on failure, forcing IPv4 resolution after the first attempt.
+    """
     if dest.exists():
         return dest
     dest.parent.mkdir(parents=True, exist_ok=True)
     print(f"  Downloading {dest.name}...")
-    try:
-        urllib.request.urlretrieve(url, dest)
-    except Exception as e:
-        dest.unlink(missing_ok=True)
-        raise RuntimeError(f"Failed to download {url}: {e}") from e
+    last_err = None
+    for attempt in range(1, retries + 1):
+        force_ipv4 = attempt > 1
+        if force_ipv4:
+            socket.getaddrinfo = _ipv4_only_getaddrinfo
+        try:
+            urllib.request.urlretrieve(url, dest)
+            break
+        except Exception as e:  # noqa: BLE001 - reported via RuntimeError below
+            last_err = e
+            dest.unlink(missing_ok=True)
+            if attempt < retries:
+                print(f"  Attempt {attempt} failed ({e}); retrying (IPv4-only)...")
+        finally:
+            if force_ipv4:
+                socket.getaddrinfo = _orig_getaddrinfo
+    else:
+        raise RuntimeError(f"Failed to download {url}: {last_err}") from last_err
     size_kb = dest.stat().st_size / 1024
     print(f"  Downloaded {dest.name} ({size_kb:.0f} KB)")
     return dest

lib/EpdFont/scripts/sd-fonts.yaml

@@ -132,7 +132,16 @@ families:
       bold:       {url: "https://raw.githubusercontent.com/impallari/Libre-Baskerville/master/fonts/ttf/LibreBaskerville-Bold.ttf"}
       italic:     {url: "https://raw.githubusercontent.com/impallari/Libre-Baskerville/master/fonts/ttf/LibreBaskerville-Italic.ttf"}
       bolditalic: {url: "https://raw.githubusercontent.com/impallari/Libre-Baskerville/master/fonts/ttf/LibreBaskerville-BoldItalic.ttf"}
-    
+
+  - name: Vollkorn
+    description: "A serif for bread and butter use by Friedrich Althausen (Latin, Greek, Cyrillic)"
+    intervals: latin-ext,greek,cyrillic
+    sizes: [12, 14, 16, 18]
+    styles:
+      regular:    {url: "https://raw.githubusercontent.com/google/fonts/main/ofl/vollkorn/Vollkorn%5Bwght%5D.ttf", variable: {wght: 400}}
+      bold:       {url: "https://raw.githubusercontent.com/google/fonts/main/ofl/vollkorn/Vollkorn%5Bwght%5D.ttf", variable: {wght: 700}}
+      italic:     {url: "https://raw.githubusercontent.com/google/fonts/main/ofl/vollkorn/Vollkorn-Italic%5Bwght%5D.ttf", variable: {wght: 400}}
+      bolditalic: {url: "https://raw.githubusercontent.com/google/fonts/main/ofl/vollkorn/Vollkorn-Italic%5Bwght%5D.ttf", variable: {wght: 700}}
 
   # ── Sans-serif ─────────────────────────────────────────────────────────
 

lib/Epub/Epub/Section.h

@@ -3,11 +3,14 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <vector>
 
 #include "Epub.h"
 
 class Page;
 class GfxRenderer;
+class ChapterHtmlSlimParser;
+class CssParser;
 
 class Section {
   std::shared_ptr<Epub> epub;
@@ -21,16 +24,67 @@ class Section {
                               bool embeddedStyle, uint8_t imageRendering, bool focusReadingEnabled);
   uint32_t onPageComplete(std::unique_ptr<Page> page);
 
+  // Page-offset table entry, kept in RAM while an incremental build is running so
+  // already-built pages can be located in the partially-written .bin.
+  struct PageLutEntry {
+    uint32_t fileOffset;
+    uint16_t paragraphIndex;
+    uint16_t listItemIndex;
+  };
+  // Held only while an incremental build is in progress (see startBuild). Carries the
+  // live parser plus the strings it references (the parser stores them by reference)
+  // and the in-RAM page-offset table.
+  struct BuildContext {
+    std::unique_ptr<ChapterHtmlSlimParser> parser;
+    std::vector<PageLutEntry> lut;
+    std::string parsePath;
+    std::string contentBase;
+    std::string imageBasePath;
+    std::string htmlPath;
+    std::string tmpHtmlPath;
+    bool reusedHtml = false;
+    CssParser* cssParser = nullptr;
+    // HTML byte progress, for estimating the section's total page count while it's still building.
+    uint32_t bytesConsumed = 0;
+    uint32_t totalBytes = 0;
+    // Exponentially-smoothed page-count estimate (0 = not yet seeded) and the bytesConsumed at its
+    // last update. The raw byte-ratio estimate jitters as the build crosses dense/sparse regions;
+    // the EMA is stepped once per build advance (not per redraw) to damp that wobble.
+    float smoothedEstimate = 0;
+    uint32_t smoothedAtConsumed = 0;
+  };
+  std::unique_ptr<BuildContext> build_;
+  bool buildComplete_ = false;
+  // Pages laid out by the active build (== build_->lut.size()). Distinct from pageCount,
+  // which is the pages *available to read* and also counts a loaded partial file's pages.
+  uint16_t builtPageCount_ = 0;
+  // A partial section file (suspended build from a previous session) is loaded at filePath.
+  // Its pages 0..partialPageCount_-1 are readable while a rebuild extends past them.
+  bool partial_ = false;
+  uint16_t partialPageCount_ = 0;
+  // Parse watermark from the partial's trailer, for estimating the total page count.
+  uint32_t partialBytesConsumed_ = 0;
+  uint32_t partialTotalBytes_ = 0;
+  bool finalizeBuild();
+  // Write the LUTs/anchor map (and, for a partial, the watermark trailer), patch the
+  // header, stamp the version byte, and swap the tmp .bin over filePath.
+  bool commitBuildFile(uint8_t version, uint32_t bytesConsumed, uint32_t totalBytes);
+  // Builds write here and are swapped over filePath only on commit, so a prior
+  // partial/finalized file stays readable while a rebuild is in progress.
+  std::string binTmpPath() const { return filePath + ".part"; }
+  std::unique_ptr<Page> loadPageAt(int page) const;
+  // Read a page already laid out by the in-progress build (page < build LUT size), from
+  // the partially-written tmp .bin without disturbing the build's write cursor.
+  std::unique_ptr<Page> loadPageDuringBuild(int page);
+
  public:
   uint16_t pageCount = 0;
   int currentPage = 0;
 
-  explicit Section(const std::shared_ptr<Epub>& epub, const int spineIndex, GfxRenderer& renderer)
-      : epub(epub),
-        spineIndex(spineIndex),
-        renderer(renderer),
-        filePath(epub->getCachePath() + "/sections/" + std::to_string(spineIndex) + ".bin") {}
-  ~Section() = default;
+  // Constructor and destructor are out-of-line: BuildContext holds a unique_ptr to the
+  // forward-declared ChapterHtmlSlimParser, whose full definition is only visible in the .cpp.
+  explicit Section(const std::shared_ptr<Epub>& epub, int spineIndex, GfxRenderer& renderer);
+  ~Section();
   bool loadSectionFile(int fontId, float lineCompression, bool extraParagraphSpacing, uint8_t paragraphAlignment,
                        uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle,
                        uint8_t imageRendering, bool focusReadingEnabled);
@@ -39,12 +93,56 @@ class Section {
                          uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle,
                          uint8_t imageRendering, bool focusReadingEnabled,
                          const std::function<void()>& popupFn = nullptr);
-  std::unique_ptr<Page> loadPageFromSectionFile();
+
+  // Incremental build: lay out the section a few pages at a time so a large chapter
+  // can show its first page immediately and keep the UI responsive while the rest
+  // builds. createSectionFile() above is the one-shot wrapper over these.
+  //   if (!startBuild(...)) fail;
+  //   each tick: buildSomeMore(N); render up to pageCount; when isBuildComplete() stop.
+  bool startBuild(int fontId, float lineCompression, bool extraParagraphSpacing, uint8_t paragraphAlignment,
+                  uint16_t viewportWidth, uint16_t viewportHeight, bool hyphenationEnabled, bool embeddedStyle,
+                  uint8_t imageRendering, bool focusReadingEnabled, const std::function<void()>& popupFn = nullptr);
+  // Lay out up to maxPages more pages (maxPages <= 0 = build to completion). Returns
+  // false on error (the build is abandoned). Sets isBuildComplete() when finished.
+  bool buildSomeMore(int maxPages);
+  bool isBuilding() const { return static_cast<bool>(build_); }
+  bool isBuildComplete() const { return buildComplete_; }
+  // Best-known total page count: the exact pageCount once finalized, or a smoothed byte-based
+  // estimate (pages so far scaled by totalBytes/bytesConsumed, damped by an EMA) while a giant spine
+  // is still building, so "page X of Y" / progress don't read off the small build watermark.
+  uint16_t estimatedTotalPages() const;
+  void abandonBuild();
+  // Persist an in-progress build as a partial section file (version sentinel + LUTs +
+  // watermark trailer) instead of discarding it, so the next open of this spine can show
+  // its pages instantly and only rebuild in the background. Called by the destructor, so
+  // any teardown path (exit, sleep, navigation) keeps the work already done. Keeps a
+  // pre-existing partial when it covers more pages than this build reached.
+  void suspendBuild();
+  // True when a partial file was loaded: pageCount is a watermark, not the chapter total.
+  bool isPartial() const { return partial_; }
+
+  // Unified page read: from the active build if it has reached the page, otherwise from
+  // the on-disk file (finalized section, or a partial the rebuild hasn't caught up to).
+  std::unique_ptr<Page> loadPage(int page);
+
   std::string getTextFromSectionFile();
 
+  // Resolve an anchor from the in-progress build first, then the on-disk anchor map
+  // (covers finalized sections and partials from a previous session).
+  std::optional<uint16_t> findAnchor(const std::string& anchor) const;
+
+  // True if this spine's unzipped HTML is already cached, so a build won't pay the (multi-second on a
+  // giant spine) zip inflation. Lets the reader skip the indexing popup on a fast reopen/rebuild.
+  bool hasHtmlCache() const;
+
   // Look up the page number for an anchor id from the section cache file.
   std::optional<uint16_t> getPageForAnchor(const std::string& anchor) const;
 
+  // Look up an anchor among the pages built so far by the in-progress build, so an anchor jump
+  // (TOC / chapter select, usually the chapter top = page 0) can resolve without laying out the
+  // whole chapter. Returns nullopt if the anchor hasn't been reached yet (build more) or no build.
+  std::optional<uint16_t> findAnchorDuringBuild(const std::string& anchor) const;
+
   // Get the page count from the section cache file without fully loading it.
   std::optional<uint16_t> getCachedPageCount() const;
 

lib/Epub/Epub/blocks/TextBlock.cpp

@@ -21,6 +21,39 @@ void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int
 
   const bool scanning = renderer.isFontCacheScanning();
   const int ascender = renderer.getFontAscenderSize(fontId);
+
+  struct DecorationLineTracker {
+    EpdFontFamily::Style style;
+    int yOffset;
+    int startX = -1;
+    int endX = -1;
+    int yPos = 0;
+
+    bool active() const { return startX != -1; }
+    void reset() {
+      startX = -1;
+      endX = -1;
+      yPos = 0;
+    }
+  };
+
+  DecorationLineTracker decorationLines[] = {
+      {EpdFontFamily::UNDERLINE, ascender + 2},
+      {EpdFontFamily::STRIKETHROUGH, ascender * 4 / 5},
+  };
+
+  const auto flushDecoration = [&](DecorationLineTracker& line) {
+    if (line.active()) {
+      renderer.drawLine(line.startX, line.yPos, line.endX, line.yPos, 2, true);
+      line.reset();
+    }
+  };
+  const auto flushDecorations = [&]() {
+    for (auto& line : decorationLines) {
+      flushDecoration(line);
+    }
+  };
+
   for (size_t i = 0; i < words.size(); i++) {
     const int wordX = wordXpos[i] + x;
     const EpdFontFamily::Style currentStyle = wordStyles[i];
@@ -59,18 +92,51 @@ void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int
       renderer.drawText(fontId, wordX, wordY, words[i].c_str(), true, currentStyle, baseDir);
     }
 
-    if (!scanning && (currentStyle & EpdFontFamily::UNDERLINE) != 0) {
+    if (scanning) {
+      continue;
+    }
+
+    if (EpdFontFamily::hasTextDecoration(currentStyle)) {
       const std::string& w = words[i];
-      int underlineWidth = renderer.getTextWidth(fontId, w.c_str(), currentStyle, baseDir);
-      const int underlineY = wordY + ascender + 2;
+      int lineStartX = wordX;
+      int lineWidth = renderer.getTextWidth(fontId, w.c_str(), currentStyle, baseDir);
 
       if ((currentStyle & (EpdFontFamily::SUP | EpdFontFamily::SUB)) != 0) {
-        underlineWidth = (underlineWidth + 1) / 2;
+        lineWidth = (lineWidth + 1) / 2;
       }
 
-      renderer.drawLine(wordX, underlineY, wordX + underlineWidth, underlineY, true);
+      // Do not decorate the synthetic em-space used for paragraph indentation.
+      if (w.size() >= 3 && static_cast<uint8_t>(w[0]) == 0xE2 && static_cast<uint8_t>(w[1]) == 0x80 &&
+          static_cast<uint8_t>(w[2]) == 0x83) {
+        const char* visibleText = w.c_str() + 3;
+        lineStartX += renderer.getTextAdvanceX(fontId, "\xe2\x80\x83", currentStyle);
+        lineWidth = renderer.getTextWidth(fontId, visibleText, currentStyle, baseDir);
+        if ((currentStyle & (EpdFontFamily::SUP | EpdFontFamily::SUB)) != 0) {
+          lineWidth = (lineWidth + 1) / 2;
+        }
+      }
+
+      for (auto& line : decorationLines) {
+        if ((currentStyle & line.style) == 0) {
+          flushDecoration(line);
+          continue;
+        }
+
+        const int lineY = wordY + line.yOffset;
+        if (line.active() && line.yPos != lineY) {
+          flushDecoration(line);
+        }
+        if (!line.active()) {
+          line.startX = lineStartX;
+          line.yPos = lineY;
+        }
+        line.endX = lineStartX + lineWidth;
+      }
+    } else {
+      flushDecorations();
     }
   }
+  flushDecorations();
 }
 
 bool TextBlock::serialize(HalFile& file) const {

lib/Epub/Epub/css/CssParser.cpp

@@ -67,13 +67,6 @@ constexpr bool iequalsAscii(std::string_view value, std::string_view lowercaseKe
                     [](char a, char b) { return asciiToLower(a) == b; });
 }
 
-// Case-insensitive ASCII substring search. Only needed by text-decoration,
-// which accepts multi-value strings like "underline solid red".
-constexpr bool icontainsAscii(std::string_view value, std::string_view lowercaseKeyword) {
-  return std::search(value.begin(), value.end(), lowercaseKeyword.begin(), lowercaseKeyword.end(),
-                     [](char a, char b) { return asciiToLower(a) == b; }) != value.end();
-}
-
 // Walk s and invoke fn(token) for each non-empty run between delimiters.
 // Tokens are boundary-trimmed and yielded as string_views into s; no
 // allocation. Runs of consecutive delimiters coalesce — no empty tokens are
@@ -252,11 +245,20 @@ CssFontWeight CssParser::interpretFontWeight(std::string_view val) {
 }
 
 CssTextDecoration CssParser::interpretDecoration(std::string_view val) {
-  // text-decoration can have multiple space-separated values
-  if (icontainsAscii(val, "underline")) {
-    return CssTextDecoration::Underline;
-  }
-  return CssTextDecoration::None;
+  // text-decoration can have multiple space-separated values. Compare whole tokens
+  // so malformed values like "notunderline" do not accidentally enable a line.
+  CssTextDecoration result = CssTextDecoration::None;
+  bool explicitNone = false;
+  forEachDelimitedToken(val, isCssWhitespace, [&](const std::string_view token) {
+    if (iequalsAscii(token, "none")) {
+      explicitNone = true;
+    } else if (iequalsAscii(token, "underline")) {
+      result = result | CssTextDecoration::Underline;
+    } else if (iequalsAscii(token, "line-through")) {
+      result = result | CssTextDecoration::LineThrough;
+    }
+  });
+  return explicitNone ? CssTextDecoration::None : result;
 }
 
 CssLength CssParser::interpretLength(std::string_view val) {
@@ -868,7 +870,7 @@ bool CssParser::loadFromCache() {
       rulesBySelector_.clear();
       return false;
     }
-    style.textDecoration = static_cast<CssTextDecoration>(enumVal);
+    style.textDecoration = static_cast<CssTextDecoration>(enumVal & CSS_TEXT_DECORATION_MASK);
 
     if (file.read(&enumVal, 1) != 1) {
       rulesBySelector_.clear();

lib/Epub/Epub/css/CssParser.h

@@ -33,7 +33,7 @@
 class CssParser {
  public:
   // Bump when CSS cache format or rules change; section caches are invalidated when this changes
-  static constexpr uint8_t CSS_CACHE_VERSION = 6;
+  static constexpr uint8_t CSS_CACHE_VERSION = 7;
 
   explicit CssParser(std::string cachePath) : cachePath(std::move(cachePath)) {}
   ~CssParser() = default;

lib/Epub/Epub/css/CssStyle.h

@@ -52,8 +52,19 @@ enum class CssFontStyle : uint8_t { Normal = 0, Italic = 1 };
 // Font weight options - CSS supports 100-900, we simplify to normal/bold
 enum class CssFontWeight : uint8_t { Normal = 0, Bold = 1 };
 
-// Text decoration options
-enum class CssTextDecoration : uint8_t { None = 0, Underline = 1 };
+// Text decoration options. Values are bit flags so CSS can combine multiple line decorations.
+enum class CssTextDecoration : uint8_t { None = 0, Underline = 1, LineThrough = 2 };
+
+constexpr CssTextDecoration operator|(const CssTextDecoration a, const CssTextDecoration b) {
+  return static_cast<CssTextDecoration>(static_cast<uint8_t>(a) | static_cast<uint8_t>(b));
+}
+
+constexpr CssTextDecoration operator&(const CssTextDecoration a, const CssTextDecoration b) {
+  return static_cast<CssTextDecoration>(static_cast<uint8_t>(a) & static_cast<uint8_t>(b));
+}
+
+constexpr uint8_t CSS_TEXT_DECORATION_MASK =
+    static_cast<uint8_t>(CssTextDecoration::Underline) | static_cast<uint8_t>(CssTextDecoration::LineThrough);
 
 // Display options - only None and Block are relevant for e-ink rendering
 enum class CssDisplay : uint8_t { Block = 0, None = 1 };

lib/Epub/Epub/parsers/ChapterHtmlSlimParser.cpp

@@ -34,6 +34,7 @@ constexpr const char* BLOCK_TAGS[] = {"p", "li", "div", "br", "blockquote"};
 constexpr const char* BOLD_TAGS[] = {"b", "strong"};
 constexpr const char* ITALIC_TAGS[] = {"i", "em"};
 constexpr const char* UNDERLINE_TAGS[] = {"u", "ins"};
+constexpr const char* LINETHROUGH_TAGS[] = {"del", "s", "strike"};
 constexpr const char* IMAGE_TAGS[] = {"img"};
 constexpr const char* SKIP_TAGS[] = {"head"};
 
@@ -89,13 +90,50 @@ void ChapterHtmlSlimParser::applyDirectionToEntry(StyleStackEntry& entry, const
   }
 }
 
-// Update effective bold/italic/underline based on block style and inline style stack
+EpdFontFamily::Style ChapterHtmlSlimParser::fontStyleForTextDecoration(const CssTextDecoration decoration) {
+  EpdFontFamily::Style style = EpdFontFamily::REGULAR;
+  if ((decoration & CssTextDecoration::Underline) != CssTextDecoration::None) {
+    style = static_cast<EpdFontFamily::Style>(style | EpdFontFamily::UNDERLINE);
+  }
+  if ((decoration & CssTextDecoration::LineThrough) != CssTextDecoration::None) {
+    style = static_cast<EpdFontFamily::Style>(style | EpdFontFamily::STRIKETHROUGH);
+  }
+  return style;
+}
+
+void ChapterHtmlSlimParser::applyTextDecorationToEntry(StyleStackEntry& entry, const CssStyle& css) {
+  if (css.hasTextDecoration()) {
+    entry.hasTextDecoration = true;
+    entry.textDecoration = css.textDecoration;
+  }
+}
+
+void ChapterHtmlSlimParser::pushDecorationStyleEntry(const CssTextDecoration defaultDecoration,
+                                                     const CssStyle& cssStyle) {
+  StyleStackEntry entry;
+  entry.depth = depth;
+  entry.hasTextDecoration = true;
+  entry.textDecoration = cssStyle.hasTextDecoration() ? cssStyle.textDecoration : defaultDecoration;
+  if (cssStyle.hasFontWeight()) {
+    entry.hasBold = true;
+    entry.bold = cssStyle.fontWeight == CssFontWeight::Bold;
+  }
+  if (cssStyle.hasFontStyle()) {
+    entry.hasItalic = true;
+    entry.italic = cssStyle.fontStyle == CssFontStyle::Italic;
+  }
+  applyDirectionToEntry(entry, cssStyle);
+  inlineStyleStack.push_back(entry);
+  updateEffectiveInlineStyle();
+}
+
+// Update effective bold/italic/decorations based on block style and inline style stack
 void ChapterHtmlSlimParser::updateEffectiveInlineStyle() {
   // Start with block-level styles
   effectiveBold = currentCssStyle.hasFontWeight() && currentCssStyle.fontWeight == CssFontWeight::Bold;
   effectiveItalic = currentCssStyle.hasFontStyle() && currentCssStyle.fontStyle == CssFontStyle::Italic;
-  effectiveUnderline =
-      currentCssStyle.hasTextDecoration() && currentCssStyle.textDecoration == CssTextDecoration::Underline;
+  effectiveTextDecoration =
+      currentCssStyle.hasTextDecoration() ? currentCssStyle.textDecoration : CssTextDecoration::None;
   effectiveDirectionDefined = currentCssStyle.hasDirection();
   effectiveDirection = currentCssStyle.direction;
   effectiveSup = false;
@@ -109,8 +147,10 @@ void ChapterHtmlSlimParser::updateEffectiveInlineStyle() {
     if (entry.hasItalic) {
       effectiveItalic = entry.italic;
     }
-    if (entry.hasUnderline) {
-      effectiveUnderline = entry.underline;
+    // CSS line decorations propagate through descendants; child entries add
+    // their own lines but cannot cancel an ancestor's already active line.
+    if (entry.hasTextDecoration) {
+      effectiveTextDecoration = effectiveTextDecoration | entry.textDecoration;
     }
     if (entry.hasDirection) {
       effectiveDirectionDefined = true;
@@ -164,7 +204,6 @@ void ChapterHtmlSlimParser::flushPartWordBuffer() {
   // Determine font style from depth-based tracking and CSS effective style
   const bool isBold = boldUntilDepth < depth || effectiveBold;
   const bool isItalic = italicUntilDepth < depth || effectiveItalic;
-  const bool isUnderline = underlineUntilDepth < depth || effectiveUnderline;
 
   // Combine style flags using bitwise OR
   EpdFontFamily::Style fontStyle = EpdFontFamily::REGULAR;
@@ -174,9 +213,7 @@ void ChapterHtmlSlimParser::flushPartWordBuffer() {
   if (isItalic) {
     fontStyle = static_cast<EpdFontFamily::Style>(fontStyle | EpdFontFamily::ITALIC);
   }
-  if (isUnderline) {
-    fontStyle = static_cast<EpdFontFamily::Style>(fontStyle | EpdFontFamily::UNDERLINE);
-  }
+  fontStyle = static_cast<EpdFontFamily::Style>(fontStyle | fontStyleForTextDecoration(effectiveTextDecoration));
   if (effectiveSup) {
     fontStyle = static_cast<EpdFontFamily::Style>(fontStyle | EpdFontFamily::SUP);
   } else if (effectiveSub) {
@@ -420,14 +457,15 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
     headerStyle.bold = false;
     headerStyle.hasItalic = true;
     headerStyle.italic = true;
-    headerStyle.hasUnderline = true;
-    headerStyle.underline = false;
     self->inlineStyleStack.push_back(headerStyle);
     self->updateEffectiveInlineStyle();
+    const CssTextDecoration savedTextDecoration = self->effectiveTextDecoration;
+    self->effectiveTextDecoration = CssTextDecoration::None;
     self->characterData(userData, headerText.c_str(), static_cast<int>(headerText.length()));
     if (self->partWordBufferIndex > 0) {
       self->flushPartWordBuffer();
     }
+    self->effectiveTextDecoration = savedTextDecoration;
     self->nextWordContinues = false;
     self->inlineStyleStack.pop_back();
     self->updateEffectiveInlineStyle();
@@ -760,12 +798,11 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
       self->currentFootnote.number[0] = '\0';
       self->currentFootnoteLinkTextLen = 0;
 
-      // Apply underline style to visually indicate the link
-      self->underlineUntilDepth = std::min(self->underlineUntilDepth, self->depth);
+      // Apply underline style to visually indicate the link.
       StyleStackEntry entry;
       entry.depth = self->depth;
-      entry.hasUnderline = true;
-      entry.underline = true;
+      entry.hasTextDecoration = true;
+      entry.textDecoration = CssTextDecoration::Underline;
       applyDirectionToEntry(entry, cssStyle);
       self->inlineStyleStack.push_back(entry);
       self->updateEffectiveInlineStyle();
@@ -837,23 +874,14 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
       self->flushPartWordBuffer();
       self->nextWordContinues = true;
     }
-    self->underlineUntilDepth = std::min(self->underlineUntilDepth, self->depth);
-    // Push inline style entry for underline tag
-    StyleStackEntry entry;
-    entry.depth = self->depth;  // Track depth for matching pop
-    entry.hasUnderline = true;
-    entry.underline = true;
-    if (cssStyle.hasFontWeight()) {
-      entry.hasBold = true;
-      entry.bold = cssStyle.fontWeight == CssFontWeight::Bold;
+    self->pushDecorationStyleEntry(CssTextDecoration::Underline, cssStyle);
+  } else if (matches(name, LINETHROUGH_TAGS, std::size(LINETHROUGH_TAGS))) {
+    // Flush buffer before style change so preceding text gets current style
+    if (self->partWordBufferIndex > 0) {
+      self->flushPartWordBuffer();
+      self->nextWordContinues = true;
     }
-    if (cssStyle.hasFontStyle()) {
-      entry.hasItalic = true;
-      entry.italic = cssStyle.fontStyle == CssFontStyle::Italic;
-    }
-    applyDirectionToEntry(entry, cssStyle);
-    self->inlineStyleStack.push_back(entry);
-    self->updateEffectiveInlineStyle();
+    self->pushDecorationStyleEntry(CssTextDecoration::LineThrough, cssStyle);
   } else if (matches(name, BOLD_TAGS, std::size(BOLD_TAGS))) {
     // Flush buffer before style change so preceding text gets current style
     if (self->partWordBufferIndex > 0) {
@@ -870,10 +898,7 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
       entry.hasItalic = true;
       entry.italic = cssStyle.fontStyle == CssFontStyle::Italic;
     }
-    if (cssStyle.hasTextDecoration()) {
-      entry.hasUnderline = true;
-      entry.underline = cssStyle.textDecoration == CssTextDecoration::Underline;
-    }
+    applyTextDecorationToEntry(entry, cssStyle);
     applyDirectionToEntry(entry, cssStyle);
     self->inlineStyleStack.push_back(entry);
     self->updateEffectiveInlineStyle();
@@ -893,10 +918,7 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
       entry.hasBold = true;
       entry.bold = cssStyle.fontWeight == CssFontWeight::Bold;
     }
-    if (cssStyle.hasTextDecoration()) {
-      entry.hasUnderline = true;
-      entry.underline = cssStyle.textDecoration == CssTextDecoration::Underline;
-    }
+    applyTextDecorationToEntry(entry, cssStyle);
     applyDirectionToEntry(entry, cssStyle);
     self->inlineStyleStack.push_back(entry);
     self->updateEffectiveInlineStyle();
@@ -935,10 +957,7 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
         entry.hasItalic = true;
         entry.italic = cssStyle.fontStyle == CssFontStyle::Italic;
       }
-      if (cssStyle.hasTextDecoration()) {
-        entry.hasUnderline = true;
-        entry.underline = cssStyle.textDecoration == CssTextDecoration::Underline;
-      }
+      applyTextDecorationToEntry(entry, cssStyle);
       applyDirectionToEntry(entry, cssStyle);
       if (cssStyle.hasVerticalAlign()) {
         if (cssStyle.verticalAlign == CssVerticalAlign::Super) {
@@ -1150,9 +1169,8 @@ void XMLCALL ChapterHtmlSlimParser::endElement(void* userData, const XML_Char* n
       !self->inlineStyleStack.empty() && self->inlineStyleStack.back().depth == self->depth - 1;
   const bool willClearBold = self->boldUntilDepth == self->depth - 1;
   const bool willClearItalic = self->italicUntilDepth == self->depth - 1;
-  const bool willClearUnderline = self->underlineUntilDepth == self->depth - 1;
 
-  const bool styleWillChange = willPopStyleStack || willClearBold || willClearItalic || willClearUnderline;
+  const bool styleWillChange = willPopStyleStack || willClearBold || willClearItalic;
   const bool headerOrBlockTag = isHeaderOrBlock(name);
   const bool tableStructuralTag = isTableStructuralTag(name);
 
@@ -1171,7 +1189,8 @@ void XMLCALL ChapterHtmlSlimParser::endElement(void* userData, const XML_Char* n
                              !matches(name, IMAGE_TAGS, std::size(IMAGE_TAGS)) && self->depth != 1;
     const bool shouldFlush = styleWillChange || headerOrBlockTag || matches(name, BOLD_TAGS, std::size(BOLD_TAGS)) ||
                              matches(name, ITALIC_TAGS, std::size(ITALIC_TAGS)) ||
-                             matches(name, UNDERLINE_TAGS, std::size(UNDERLINE_TAGS)) || tableStructuralTag ||
+                             matches(name, UNDERLINE_TAGS, std::size(UNDERLINE_TAGS)) ||
+                             matches(name, LINETHROUGH_TAGS, std::size(LINETHROUGH_TAGS)) || tableStructuralTag ||
                              matches(name, IMAGE_TAGS, std::size(IMAGE_TAGS)) || self->depth == 1;
 
     if (shouldFlush) {
@@ -1230,11 +1249,6 @@ void XMLCALL ChapterHtmlSlimParser::endElement(void* userData, const XML_Char* n
     self->italicUntilDepth = INT_MAX;
   }
 
-  // Leaving underline tag
-  if (self->underlineUntilDepth == self->depth) {
-    self->underlineUntilDepth = INT_MAX;
-  }
-
   // Pop from inline style stack if we pushed an entry at this depth
   // This handles all inline elements: b, i, u, span, etc.
   if (!self->inlineStyleStack.empty() && self->inlineStyleStack.back().depth == self->depth) {
@@ -1261,7 +1275,9 @@ void XMLCALL ChapterHtmlSlimParser::endElement(void* userData, const XML_Char* n
   }
 }
 
-bool ChapterHtmlSlimParser::parseAndBuildPages() {
+ChapterHtmlSlimParser::~ChapterHtmlSlimParser() { abortParse(); }
+
+bool ChapterHtmlSlimParser::beginParse() {
   // Initialize block style stack with a root entry representing "no ancestor block elements".
   // The user's paragraph alignment is set as the default so child elements without explicit
   // text-align inherit it correctly through getCombinedBlockStyle.
@@ -1279,67 +1295,78 @@ bool ChapterHtmlSlimParser::parseAndBuildPages() {
   paragraphAlignmentBlockStyle.alignment = align;
   startNewTextBlock(paragraphAlignmentBlockStyle);
 
-  XML_Parser parser = XML_ParserCreate(nullptr);
-  int done;
-
-  if (!parser) {
+  xmlParser_ = XML_ParserCreate(nullptr);
+  if (!xmlParser_) {
     LOG_ERR("EHP", "Couldn't allocate memory for parser");
     return false;
   }
 
   // Handle HTML entities (like &nbsp;) that aren't in XML spec or DTD
   // Using DefaultHandlerExpand preserves normal entity expansion from DOCTYPE
-  XML_SetDefaultHandlerExpand(parser, defaultHandlerExpand);
+  XML_SetDefaultHandlerExpand(xmlParser_, defaultHandlerExpand);
 
-  HalFile file;
-  if (!Storage.openFileForRead("EHP", filepath, file)) {
-    destroyXmlParser(parser);
+  if (!Storage.openFileForRead("EHP", filepath, parseFile_)) {
+    destroyXmlParser(xmlParser_);
+    xmlParser_ = nullptr;
     return false;
   }
 
   // Get file size to decide whether to show indexing popup.
-  if (popupFn && file.size() >= MIN_SIZE_FOR_POPUP) {
+  if (popupFn && parseFile_.size() >= MIN_SIZE_FOR_POPUP) {
     popupFn();
   }
 
-  XML_SetUserData(parser, this);
-  XML_SetElementHandler(parser, startElement, endElement);
-  XML_SetCharacterDataHandler(parser, characterData);
+  XML_SetUserData(xmlParser_, this);
+  XML_SetElementHandler(xmlParser_, startElement, endElement);
+  XML_SetCharacterDataHandler(xmlParser_, characterData);
 
-  // Compute the time taken to parse and build pages
-  const uint32_t chapterStartTime = millis();
-  do {
-    void* const buf = XML_GetBuffer(parser, PARSE_BUFFER_SIZE);
-    if (!buf) {
-      LOG_ERR("EHP", "Couldn't allocate memory for buffer");
-      destroyXmlParser(parser);
-      file.close();
-      return false;
-    }
+  parseStartTime_ = millis();
+  return true;
+}
 
-    const size_t len = file.read(buf, PARSE_BUFFER_SIZE);
+ChapterHtmlSlimParser::ParseStatus ChapterHtmlSlimParser::parseStep() {
+  void* const buf = XML_GetBuffer(xmlParser_, PARSE_BUFFER_SIZE);
+  if (!buf) {
+    LOG_ERR("EHP", "Couldn't allocate memory for buffer");
+    return ParseStatus::Error;
+  }
 
-    if (len == 0 && file.available() > 0) {
-      LOG_ERR("EHP", "File read error");
-      destroyXmlParser(parser);
-      file.close();
-      return false;
-    }
+  const size_t len = parseFile_.read(buf, PARSE_BUFFER_SIZE);
 
-    done = file.available() == 0;
+  if (len == 0 && parseFile_.available() > 0) {
+    LOG_ERR("EHP", "File read error");
+    return ParseStatus::Error;
+  }
 
-    if (XML_ParseBuffer(parser, static_cast<int>(len), done) == XML_STATUS_ERROR) {
-      LOG_ERR("EHP", "Parse error at line %lu:\n%s", XML_GetCurrentLineNumber(parser),
-              XML_ErrorString(XML_GetErrorCode(parser)));
-      destroyXmlParser(parser);
-      file.close();
-      return false;
-    }
-  } while (!done);
-  LOG_DBG("EHP", "Time to parse and build pages: %lu ms", millis() - chapterStartTime);
+  const int done = parseFile_.available() == 0;
 
-  destroyXmlParser(parser);
-  file.close();
+  if (XML_ParseBuffer(xmlParser_, static_cast<int>(len), done) == XML_STATUS_ERROR) {
+    LOG_ERR("EHP", "Parse error at line %lu:\n%s", XML_GetCurrentLineNumber(xmlParser_),
+            XML_ErrorString(XML_GetErrorCode(xmlParser_)));
+    return ParseStatus::Error;
+  }
+
+  return done ? ParseStatus::Done : ParseStatus::More;
+}
+
+void ChapterHtmlSlimParser::abortParse() {
+  if (xmlParser_) {
+    destroyXmlParser(xmlParser_);
+    xmlParser_ = nullptr;
+  }
+  // Only close the file if it was successfully opened in beginParse()
+  if (parseFile_.isOpen()) {
+    parseFile_.close();
+  }
+}
+
+bool ChapterHtmlSlimParser::finishParse() {
+  if (xmlParser_) {
+    LOG_DBG("EHP", "Time to parse and build pages: %lu ms", millis() - parseStartTime_);
+    destroyXmlParser(xmlParser_);
+    xmlParser_ = nullptr;
+  }
+  parseFile_.close();
 
   // Process last page if there is still text
   if (currentTextBlock) {
@@ -1357,6 +1384,23 @@ bool ChapterHtmlSlimParser::parseAndBuildPages() {
   return true;
 }
 
+bool ChapterHtmlSlimParser::parseAndBuildPages() {
+  if (!beginParse()) {
+    return false;
+  }
+  for (;;) {
+    const ParseStatus status = parseStep();
+    if (status == ParseStatus::Error) {
+      abortParse();
+      return false;
+    }
+    if (status == ParseStatus::Done) {
+      break;
+    }
+  }
+  return finishParse();
+}
+
 void ChapterHtmlSlimParser::addLineToPage(std::shared_ptr<TextBlock> line) {
   const int lineHeight = renderer.getLineHeight(fontId) * lineCompression;
 

lib/Epub/Epub/parsers/ChapterHtmlSlimParser.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <HalStorage.h>
 #include <expat.h>
 
 #include <climits>
@@ -31,7 +32,6 @@ class ChapterHtmlSlimParser {
   int skipUntilDepth = INT_MAX;
   int boldUntilDepth = INT_MAX;
   int italicUntilDepth = INT_MAX;
-  int underlineUntilDepth = INT_MAX;
   // buffer for building up words from characters, will auto break if longer than this
   // leave one char at end for null pointer
   char partWordBuffer[MAX_WORD_SIZE + 1] = {};
@@ -60,7 +60,8 @@ class ChapterHtmlSlimParser {
     int depth = 0;
     bool hasBold = false, bold = false;
     bool hasItalic = false, italic = false;
-    bool hasUnderline = false, underline = false;
+    bool hasTextDecoration = false;
+    CssTextDecoration textDecoration = CssTextDecoration::None;
     bool hasDirection = false;
     CssTextDirection direction = CssTextDirection::Ltr;
     bool hasSup = false, sup = false;
@@ -71,7 +72,7 @@ class ChapterHtmlSlimParser {
   CssStyle currentCssStyle;
   bool effectiveBold = false;
   bool effectiveItalic = false;
-  bool effectiveUnderline = false;
+  CssTextDecoration effectiveTextDecoration = CssTextDecoration::None;
   bool effectiveDirectionDefined = false;
   CssTextDirection effectiveDirection = CssTextDirection::Ltr;
   bool effectiveSup = false;
@@ -96,12 +97,25 @@ class ChapterHtmlSlimParser {
   std::vector<std::pair<int, FootnoteEntry>> pendingFootnotes;  // <wordIndex, entry>
   int wordsExtractedInBlock = 0;
 
+  // Resumable parse state. The one-shot parseAndBuildPages() drives these
+  // internally; the incremental section builder drives them across render ticks
+  // so a large single chapter can yield between pages instead of blocking the UI
+  // until the whole thing is laid out. parseFile_ and the expat parser stay alive
+  // for the lifetime of the parse so it can be paused and resumed at buffer
+  // boundaries.
+  XML_Parser xmlParser_ = nullptr;
+  HalFile parseFile_;
+  uint32_t parseStartTime_ = 0;
+
   void updateEffectiveInlineStyle();
   void startNewTextBlock(const BlockStyle& blockStyle);
   void flushPendingAnchor();
   void flushPartWordBuffer();
   void makePages();
+  static EpdFontFamily::Style fontStyleForTextDecoration(CssTextDecoration decoration);
   static void applyDirectionToEntry(StyleStackEntry& entry, const CssStyle& css);
+  static void applyTextDecorationToEntry(StyleStackEntry& entry, const CssStyle& css);
+  void pushDecorationStyleEntry(CssTextDecoration defaultDecoration, const CssStyle& cssStyle);
   void emitHorizontalRule(const BlockStyle& blockStyle);
   // XML callbacks
   static void XMLCALL startElement(void* userData, const XML_Char* name, const XML_Char** atts);
@@ -141,8 +155,28 @@ class ChapterHtmlSlimParser {
         imageBasePath(imageBasePath),
         tocAnchors(std::move(tocAnchors)) {}
 
-  ~ChapterHtmlSlimParser() = default;
+  ~ChapterHtmlSlimParser();
+
+  // One-shot parse: builds every page before returning (begin + step* + finish).
   bool parseAndBuildPages();
+
+  // Resumable parse, for the incremental section builder. Drive as:
+  //   if (!beginParse()) fail;
+  //   loop: switch (parseStep()) { More: keep going / yield; Done: finishParse(); Error: abortParse(); }
+  // Pages are emitted via completePageFn as they complete during parseStep(), so
+  // the caller can stop once enough pages are built and resume on a later tick.
+  enum class ParseStatus { More, Done, Error };
+  bool beginParse();
+  ParseStatus parseStep();
+  bool finishParse();  // flush the trailing page and tear down; returns true
+  void abortParse();   // tear down without flushing (error / abandon)
+
   void addLineToPage(std::shared_ptr<TextBlock> line);
   const std::vector<std::pair<std::string, uint16_t>>& getAnchors() const { return anchorData; }
+
+  // Byte progress of the in-flight parse, used to estimate a still-building section's total page
+  // count (a giant single-spine book never fully lays out, so its real count is unknown). Valid
+  // between beginParse() and finishParse()/abortParse().
+  size_t parseBytesConsumed() { return parseFile_ ? parseFile_.position() : 0; }
+  size_t parseTotalBytes() { return parseFile_ ? parseFile_.size() : 0; }
 };