feat(xtc): add XTC ebook format support

Add support for XTC (XTeink X4 native) ebook format with pre-rendered
bitmap pages. Key changes:

- Add Xtc library with XtcParser for reading XTC files
- XTC format: 22-byte XTG page headers with 480x800 1-bit bitmaps
- XtcReaderActivity for displaying XTC pages on e-ink display
- Correct bit polarity: 0=black, 1=white in XTC format
- FileSelectionActivity: detect and handle .xtc files
- ReaderActivity: route to XtcReaderActivity for XTC files
- Cover BMP generation from first XTC page

XTC pages include pre-rendered status bar with page numbers and
progress, so no additional overlay is needed.

lib/Xtc/Xtc.cpp

@@ -0,0 +1,262 @@
+/**
+ * Xtc.cpp
+ *
+ * Main XTC ebook class implementation
+ * XTC ebook support for CrossPoint Reader
+ */
+
+#include "Xtc.h"
+
+#include <FsHelpers.h>
+#include <HardwareSerial.h>
+#include <SD.h>
+
+bool Xtc::load() {
+  Serial.printf("[%lu] [XTC] Loading XTC: %s\n", millis(), filepath.c_str());
+
+  // Initialize parser
+  parser.reset(new xtc::XtcParser());
+
+  // Open XTC file
+  xtc::XtcError err = parser->open(filepath.c_str());
+  if (err != xtc::XtcError::OK) {
+    Serial.printf("[%lu] [XTC] Failed to load: %s\n", millis(), xtc::errorToString(err));
+    parser.reset();
+    return false;
+  }
+
+  loaded = true;
+  Serial.printf("[%lu] [XTC] Loaded XTC: %s (%lu pages)\n", millis(), filepath.c_str(), parser->getPageCount());
+  return true;
+}
+
+bool Xtc::clearCache() const {
+  if (!SD.exists(cachePath.c_str())) {
+    Serial.printf("[%lu] [XTC] Cache does not exist, no action needed\n", millis());
+    return true;
+  }
+
+  if (!FsHelpers::removeDir(cachePath.c_str())) {
+    Serial.printf("[%lu] [XTC] Failed to clear cache\n", millis());
+    return false;
+  }
+
+  Serial.printf("[%lu] [XTC] Cache cleared successfully\n", millis());
+  return true;
+}
+
+void Xtc::setupCacheDir() const {
+  if (SD.exists(cachePath.c_str())) {
+    return;
+  }
+
+  // Create directories recursively
+  for (size_t i = 1; i < cachePath.length(); i++) {
+    if (cachePath[i] == '/') {
+      SD.mkdir(cachePath.substr(0, i).c_str());
+    }
+  }
+  SD.mkdir(cachePath.c_str());
+}
+
+std::string Xtc::getTitle() const {
+  if (!loaded || !parser) {
+    return "";
+  }
+
+  // Try to get title from XTC metadata first
+  std::string title = parser->getTitle();
+  if (!title.empty()) {
+    return title;
+  }
+
+  // Fallback: extract filename from path as title
+  size_t lastSlash = filepath.find_last_of('/');
+  size_t lastDot = filepath.find_last_of('.');
+
+  if (lastSlash == std::string::npos) {
+    lastSlash = 0;
+  } else {
+    lastSlash++;
+  }
+
+  if (lastDot == std::string::npos || lastDot <= lastSlash) {
+    return filepath.substr(lastSlash);
+  }
+
+  return filepath.substr(lastSlash, lastDot - lastSlash);
+}
+
+std::string Xtc::getCoverBmpPath() const { return cachePath + "/cover.bmp"; }
+
+bool Xtc::generateCoverBmp() const {
+  // Already generated
+  if (SD.exists(getCoverBmpPath().c_str())) {
+    return true;
+  }
+
+  if (!loaded || !parser) {
+    Serial.printf("[%lu] [XTC] Cannot generate cover BMP, file not loaded\n", millis());
+    return false;
+  }
+
+  if (parser->getPageCount() == 0) {
+    Serial.printf("[%lu] [XTC] No pages in XTC file\n", millis());
+    return false;
+  }
+
+  // Setup cache directory
+  setupCacheDir();
+
+  // Get first page info for cover
+  xtc::PageInfo pageInfo;
+  if (!parser->getPageInfo(0, pageInfo)) {
+    Serial.printf("[%lu] [XTC] Failed to get first page info\n", millis());
+    return false;
+  }
+
+  // Allocate buffer for page data (XTC is always 1-bit monochrome)
+  const size_t bitmapSize = ((pageInfo.width + 7) / 8) * pageInfo.height;
+  uint8_t* pageBuffer = static_cast<uint8_t*>(malloc(bitmapSize));
+  if (!pageBuffer) {
+    Serial.printf("[%lu] [XTC] Failed to allocate page buffer (%lu bytes)\n", millis(), bitmapSize);
+    return false;
+  }
+
+  // Load first page (cover)
+  size_t bytesRead = const_cast<xtc::XtcParser*>(parser.get())->loadPage(0, pageBuffer, bitmapSize);
+  if (bytesRead == 0) {
+    Serial.printf("[%lu] [XTC] Failed to load cover page\n", millis());
+    free(pageBuffer);
+    return false;
+  }
+
+  // Create BMP file
+  File coverBmp;
+  if (!FsHelpers::openFileForWrite("XTC", getCoverBmpPath(), coverBmp)) {
+    Serial.printf("[%lu] [XTC] Failed to create cover BMP file\n", millis());
+    free(pageBuffer);
+    return false;
+  }
+
+  // Write BMP header
+  // BMP file header (14 bytes)
+  const uint32_t rowSize = ((pageInfo.width + 31) / 32) * 4;  // Row size aligned to 4 bytes
+  const uint32_t imageSize = rowSize * pageInfo.height;
+  const uint32_t fileSize = 14 + 40 + 8 + imageSize;  // Header + DIB + palette + data
+
+  // File header
+  coverBmp.write('B');
+  coverBmp.write('M');
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
+  uint32_t reserved = 0;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
+  uint32_t dataOffset = 14 + 40 + 8;  // 1-bit palette has 2 colors (8 bytes)
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
+
+  // DIB header (BITMAPINFOHEADER - 40 bytes)
+  uint32_t dibHeaderSize = 40;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
+  int32_t width = pageInfo.width;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&width), 4);
+  int32_t height = -static_cast<int32_t>(pageInfo.height);  // Negative for top-down
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&height), 4);
+  uint16_t planes = 1;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
+  uint16_t bitsPerPixel = 1;  // 1-bit monochrome
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
+  uint32_t compression = 0;  // BI_RGB (no compression)
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
+  int32_t ppmX = 2835;  // 72 DPI
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
+  int32_t ppmY = 2835;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
+  uint32_t colorsUsed = 2;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
+  uint32_t colorsImportant = 2;
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
+
+  // Color palette (2 colors for 1-bit)
+  // XTC uses inverted polarity: 0 = black, 1 = white
+  // Color 0: Black (text/foreground in XTC)
+  uint8_t black[4] = {0x00, 0x00, 0x00, 0x00};
+  coverBmp.write(black, 4);
+  // Color 1: White (background in XTC)
+  uint8_t white[4] = {0xFF, 0xFF, 0xFF, 0x00};
+  coverBmp.write(white, 4);
+
+  // Write bitmap data
+  // XTC stores data as packed bits, same as BMP 1-bit format
+  // But we need to ensure proper row alignment (4-byte boundary)
+  const size_t srcRowSize = (pageInfo.width + 7) / 8;  // Source row size
+
+  for (uint16_t y = 0; y < pageInfo.height; y++) {
+    // Write source row
+    coverBmp.write(pageBuffer + y * srcRowSize, srcRowSize);
+
+    // Pad to 4-byte boundary
+    uint8_t padding[4] = {0, 0, 0, 0};
+    size_t paddingSize = rowSize - srcRowSize;
+    if (paddingSize > 0) {
+      coverBmp.write(padding, paddingSize);
+    }
+  }
+
+  coverBmp.close();
+  free(pageBuffer);
+
+  Serial.printf("[%lu] [XTC] Generated cover BMP: %s\n", millis(), getCoverBmpPath().c_str());
+  return true;
+}
+
+uint32_t Xtc::getPageCount() const {
+  if (!loaded || !parser) {
+    return 0;
+  }
+  return parser->getPageCount();
+}
+
+uint16_t Xtc::getPageWidth() const {
+  if (!loaded || !parser) {
+    return 0;
+  }
+  return parser->getWidth();
+}
+
+uint16_t Xtc::getPageHeight() const {
+  if (!loaded || !parser) {
+    return 0;
+  }
+  return parser->getHeight();
+}
+
+size_t Xtc::loadPage(uint32_t pageIndex, uint8_t* buffer, size_t bufferSize) const {
+  if (!loaded || !parser) {
+    return 0;
+  }
+  return const_cast<xtc::XtcParser*>(parser.get())->loadPage(pageIndex, buffer, bufferSize);
+}
+
+xtc::XtcError Xtc::loadPageStreaming(uint32_t pageIndex,
+                                     std::function<void(const uint8_t* data, size_t size, size_t offset)> callback,
+                                     size_t chunkSize) const {
+  if (!loaded || !parser) {
+    return xtc::XtcError::FILE_NOT_FOUND;
+  }
+  return const_cast<xtc::XtcParser*>(parser.get())->loadPageStreaming(pageIndex, callback, chunkSize);
+}
+
+uint8_t Xtc::calculateProgress(uint32_t currentPage) const {
+  if (!loaded || !parser || parser->getPageCount() == 0) {
+    return 0;
+  }
+  return static_cast<uint8_t>((currentPage + 1) * 100 / parser->getPageCount());
+}
+
+xtc::XtcError Xtc::getLastError() const {
+  if (!parser) {
+    return xtc::XtcError::FILE_NOT_FOUND;
+  }
+  return parser->getLastError();
+}

lib/Xtc/Xtc.h

@@ -0,0 +1,96 @@
+/**
+ * Xtc.h
+ *
+ * Main XTC ebook class for CrossPoint Reader
+ * Provides EPUB-like interface for XTC file handling
+ */
+
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include "Xtc/XtcParser.h"
+#include "Xtc/XtcTypes.h"
+
+/**
+ * XTC Ebook Handler
+ *
+ * Handles XTC file loading, page access, and cover image generation.
+ * Interface is designed to be similar to Epub class for easy integration.
+ */
+class Xtc {
+  std::string filepath;
+  std::string cachePath;
+  std::unique_ptr<xtc::XtcParser> parser;
+  bool loaded;
+
+ public:
+  explicit Xtc(std::string filepath, const std::string& cacheDir) : filepath(std::move(filepath)), loaded(false) {
+    // Create cache key based on filepath (same as Epub)
+    cachePath = cacheDir + "/xtc_" + std::to_string(std::hash<std::string>{}(this->filepath));
+  }
+  ~Xtc() = default;
+
+  /**
+   * Load XTC file
+   * @return true on success
+   */
+  bool load();
+
+  /**
+   * Clear cached data
+   * @return true on success
+   */
+  bool clearCache() const;
+
+  /**
+   * Setup cache directory
+   */
+  void setupCacheDir() const;
+
+  // Path accessors
+  const std::string& getCachePath() const { return cachePath; }
+  const std::string& getPath() const { return filepath; }
+
+  // Metadata
+  std::string getTitle() const;
+
+  // Cover image support (for sleep screen)
+  std::string getCoverBmpPath() const;
+  bool generateCoverBmp() const;
+
+  // Page access
+  uint32_t getPageCount() const;
+  uint16_t getPageWidth() const;
+  uint16_t getPageHeight() const;
+
+  /**
+   * Load page bitmap data
+   * @param pageIndex Page index (0-based)
+   * @param buffer Output buffer
+   * @param bufferSize Buffer size
+   * @return Number of bytes read
+   */
+  size_t loadPage(uint32_t pageIndex, uint8_t* buffer, size_t bufferSize) const;
+
+  /**
+   * Load page with streaming callback
+   * @param pageIndex Page index
+   * @param callback Callback for each chunk
+   * @param chunkSize Chunk size
+   * @return Error code
+   */
+  xtc::XtcError loadPageStreaming(uint32_t pageIndex,
+                                  std::function<void(const uint8_t* data, size_t size, size_t offset)> callback,
+                                  size_t chunkSize = 1024) const;
+
+  // Progress calculation
+  uint8_t calculateProgress(uint32_t currentPage) const;
+
+  // Check if file is loaded
+  bool isLoaded() const { return loaded; }
+
+  // Error information
+  xtc::XtcError getLastError() const;
+};

lib/Xtc/Xtc/XtcParser.cpp

@@ -0,0 +1,290 @@
+/**
+ * XtcParser.cpp
+ *
+ * XTC file parsing implementation
+ * XTC ebook support for CrossPoint Reader
+ */
+
+#include "XtcParser.h"
+
+#include <HardwareSerial.h>
+
+#include <cstring>
+
+namespace xtc {
+
+XtcParser::XtcParser()
+    : m_isOpen(false), m_defaultWidth(DISPLAY_WIDTH), m_defaultHeight(DISPLAY_HEIGHT), m_lastError(XtcError::OK) {
+  memset(&m_header, 0, sizeof(m_header));
+}
+
+XtcParser::~XtcParser() { close(); }
+
+XtcError XtcParser::open(const char* filepath) {
+  // Close if already open
+  if (m_isOpen) {
+    close();
+  }
+
+  // Open file
+  m_file = SD.open(filepath, FILE_READ);
+  if (!m_file) {
+    Serial.printf("[%lu] [XTC] Failed to open file: %s\n", millis(), filepath);
+    m_lastError = XtcError::FILE_NOT_FOUND;
+    return m_lastError;
+  }
+
+  // Read header
+  m_lastError = readHeader();
+  if (m_lastError != XtcError::OK) {
+    Serial.printf("[%lu] [XTC] Failed to read header: %s\n", millis(), errorToString(m_lastError));
+    m_file.close();
+    return m_lastError;
+  }
+
+  // Read title if available
+  readTitle();
+
+  // Read page table
+  m_lastError = readPageTable();
+  if (m_lastError != XtcError::OK) {
+    Serial.printf("[%lu] [XTC] Failed to read page table: %s\n", millis(), errorToString(m_lastError));
+    m_file.close();
+    return m_lastError;
+  }
+
+  m_isOpen = true;
+  Serial.printf("[%lu] [XTC] Opened file: %s (%u pages, %dx%d)\n", millis(), filepath, m_header.pageCount,
+                m_defaultWidth, m_defaultHeight);
+  return XtcError::OK;
+}
+
+void XtcParser::close() {
+  if (m_isOpen) {
+    m_file.close();
+    m_isOpen = false;
+  }
+  m_pageTable.clear();
+  m_title.clear();
+  memset(&m_header, 0, sizeof(m_header));
+}
+
+XtcError XtcParser::readHeader() {
+  // Read first 56 bytes of header
+  size_t bytesRead = m_file.read(reinterpret_cast<uint8_t*>(&m_header), sizeof(XtcHeader));
+  if (bytesRead != sizeof(XtcHeader)) {
+    return XtcError::READ_ERROR;
+  }
+
+  // Verify magic number
+  if (m_header.magic != XTC_MAGIC) {
+    Serial.printf("[%lu] [XTC] Invalid magic: 0x%08X (expected 0x%08X)\n", millis(), m_header.magic, XTC_MAGIC);
+    return XtcError::INVALID_MAGIC;
+  }
+
+  // Check version
+  if (m_header.version > 1) {
+    Serial.printf("[%lu] [XTC] Unsupported version: %d\n", millis(), m_header.version);
+    return XtcError::INVALID_VERSION;
+  }
+
+  // Basic validation
+  if (m_header.pageCount == 0) {
+    return XtcError::CORRUPTED_HEADER;
+  }
+
+  Serial.printf("[%lu] [XTC] Header: magic=0x%08X, ver=%u, pages=%u, pageTableOff=%llu, dataOff=%llu\n", millis(),
+                m_header.magic, m_header.version, m_header.pageCount, m_header.pageTableOffset, m_header.dataOffset);
+
+  return XtcError::OK;
+}
+
+XtcError XtcParser::readTitle() {
+  // Title is usually at offset 0x38 (56) for 88-byte headers
+  // Read title as null-terminated UTF-8 string
+  if (m_header.titleOffset == 0) {
+    m_header.titleOffset = 0x38;  // Default offset
+  }
+
+  if (!m_file.seek(m_header.titleOffset)) {
+    return XtcError::READ_ERROR;
+  }
+
+  char titleBuf[128] = {0};
+  m_file.read(reinterpret_cast<uint8_t*>(titleBuf), sizeof(titleBuf) - 1);
+  m_title = titleBuf;
+
+  Serial.printf("[%lu] [XTC] Title: %s\n", millis(), m_title.c_str());
+  return XtcError::OK;
+}
+
+XtcError XtcParser::readPageTable() {
+  if (m_header.pageTableOffset == 0) {
+    Serial.printf("[%lu] [XTC] Page table offset is 0, cannot read\n", millis());
+    return XtcError::CORRUPTED_HEADER;
+  }
+
+  // Seek to page table
+  if (!m_file.seek(m_header.pageTableOffset)) {
+    Serial.printf("[%lu] [XTC] Failed to seek to page table at %llu\n", millis(), m_header.pageTableOffset);
+    return XtcError::READ_ERROR;
+  }
+
+  m_pageTable.resize(m_header.pageCount);
+
+  // Read page table entries
+  for (uint16_t i = 0; i < m_header.pageCount; i++) {
+    PageTableEntry entry;
+    size_t bytesRead = m_file.read(reinterpret_cast<uint8_t*>(&entry), sizeof(PageTableEntry));
+    if (bytesRead != sizeof(PageTableEntry)) {
+      Serial.printf("[%lu] [XTC] Failed to read page table entry %u\n", millis(), i);
+      return XtcError::READ_ERROR;
+    }
+
+    m_pageTable[i].offset = entry.dataOffset;
+    m_pageTable[i].size = entry.dataSize;
+    m_pageTable[i].width = entry.width;
+    m_pageTable[i].height = entry.height;
+
+    // Update default dimensions from first page
+    if (i == 0) {
+      m_defaultWidth = entry.width;
+      m_defaultHeight = entry.height;
+    }
+  }
+
+  Serial.printf("[%lu] [XTC] Read %u page table entries\n", millis(), m_header.pageCount);
+  return XtcError::OK;
+}
+
+bool XtcParser::getPageInfo(uint32_t pageIndex, PageInfo& info) const {
+  if (pageIndex >= m_pageTable.size()) {
+    return false;
+  }
+  info = m_pageTable[pageIndex];
+  return true;
+}
+
+size_t XtcParser::loadPage(uint32_t pageIndex, uint8_t* buffer, size_t bufferSize) {
+  if (!m_isOpen) {
+    m_lastError = XtcError::FILE_NOT_FOUND;
+    return 0;
+  }
+
+  if (pageIndex >= m_header.pageCount) {
+    m_lastError = XtcError::PAGE_OUT_OF_RANGE;
+    return 0;
+  }
+
+  const PageInfo& page = m_pageTable[pageIndex];
+
+  // Seek to page data
+  if (!m_file.seek(page.offset)) {
+    Serial.printf("[%lu] [XTC] Failed to seek to page %u at offset %llu\n", millis(), pageIndex, page.offset);
+    m_lastError = XtcError::READ_ERROR;
+    return 0;
+  }
+
+  // Read XTG header first
+  XtgPageHeader xtgHeader;
+  size_t headerRead = m_file.read(reinterpret_cast<uint8_t*>(&xtgHeader), sizeof(XtgPageHeader));
+  if (headerRead != sizeof(XtgPageHeader)) {
+    Serial.printf("[%lu] [XTC] Failed to read XTG header for page %u\n", millis(), pageIndex);
+    m_lastError = XtcError::READ_ERROR;
+    return 0;
+  }
+
+  // Verify XTG magic
+  if (xtgHeader.magic != XTG_MAGIC) {
+    Serial.printf("[%lu] [XTC] Invalid XTG magic for page %u: 0x%08X\n", millis(), pageIndex, xtgHeader.magic);
+    m_lastError = XtcError::INVALID_MAGIC;
+    return 0;
+  }
+
+  // Calculate bitmap size
+  const size_t bitmapSize = ((xtgHeader.width + 7) / 8) * xtgHeader.height;
+
+  // Check buffer size
+  if (bufferSize < bitmapSize) {
+    Serial.printf("[%lu] [XTC] Buffer too small: need %u, have %u\n", millis(), bitmapSize, bufferSize);
+    m_lastError = XtcError::MEMORY_ERROR;
+    return 0;
+  }
+
+  // Read bitmap data
+  size_t bytesRead = m_file.read(buffer, bitmapSize);
+  if (bytesRead != bitmapSize) {
+    Serial.printf("[%lu] [XTC] Page read error: expected %u, got %u\n", millis(), bitmapSize, bytesRead);
+    m_lastError = XtcError::READ_ERROR;
+    return 0;
+  }
+
+  m_lastError = XtcError::OK;
+  return bytesRead;
+}
+
+XtcError XtcParser::loadPageStreaming(uint32_t pageIndex,
+                                      std::function<void(const uint8_t* data, size_t size, size_t offset)> callback,
+                                      size_t chunkSize) {
+  if (!m_isOpen) {
+    return XtcError::FILE_NOT_FOUND;
+  }
+
+  if (pageIndex >= m_header.pageCount) {
+    return XtcError::PAGE_OUT_OF_RANGE;
+  }
+
+  const PageInfo& page = m_pageTable[pageIndex];
+
+  // Seek to page data
+  if (!m_file.seek(page.offset)) {
+    return XtcError::READ_ERROR;
+  }
+
+  // Read and skip XTG header
+  XtgPageHeader xtgHeader;
+  size_t headerRead = m_file.read(reinterpret_cast<uint8_t*>(&xtgHeader), sizeof(XtgPageHeader));
+  if (headerRead != sizeof(XtgPageHeader) || xtgHeader.magic != XTG_MAGIC) {
+    return XtcError::READ_ERROR;
+  }
+
+  // Calculate bitmap size
+  const size_t bitmapSize = ((xtgHeader.width + 7) / 8) * xtgHeader.height;
+
+  // Read in chunks
+  std::vector<uint8_t> chunk(chunkSize);
+  size_t totalRead = 0;
+
+  while (totalRead < bitmapSize) {
+    size_t toRead = std::min(chunkSize, bitmapSize - totalRead);
+    size_t bytesRead = m_file.read(chunk.data(), toRead);
+
+    if (bytesRead == 0) {
+      return XtcError::READ_ERROR;
+    }
+
+    callback(chunk.data(), bytesRead, totalRead);
+    totalRead += bytesRead;
+  }
+
+  return XtcError::OK;
+}
+
+bool XtcParser::isValidXtcFile(const char* filepath) {
+  File file = SD.open(filepath, FILE_READ);
+  if (!file) {
+    return false;
+  }
+
+  uint32_t magic = 0;
+  size_t bytesRead = file.read(reinterpret_cast<uint8_t*>(&magic), sizeof(magic));
+  file.close();
+
+  if (bytesRead != sizeof(magic)) {
+    return false;
+  }
+
+  return (magic == XTC_MAGIC);
+}
+
+}  // namespace xtc

lib/Xtc/Xtc/XtcParser.h

@@ -0,0 +1,94 @@
+/**
+ * XtcParser.h
+ *
+ * XTC file parsing and page data extraction
+ * XTC ebook support for CrossPoint Reader
+ */
+
+#pragma once
+
+#include <SD.h>
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "XtcTypes.h"
+
+namespace xtc {
+
+/**
+ * XTC File Parser
+ *
+ * Reads XTC files from SD card and extracts page data.
+ * Designed for ESP32-C3's limited RAM (~380KB) using streaming.
+ */
+class XtcParser {
+ public:
+  XtcParser();
+  ~XtcParser();
+
+  // File open/close
+  XtcError open(const char* filepath);
+  void close();
+  bool isOpen() const { return m_isOpen; }
+
+  // Header information access
+  const XtcHeader& getHeader() const { return m_header; }
+  uint16_t getPageCount() const { return m_header.pageCount; }
+  uint16_t getWidth() const { return m_defaultWidth; }
+  uint16_t getHeight() const { return m_defaultHeight; }
+
+  // Page information
+  bool getPageInfo(uint32_t pageIndex, PageInfo& info) const;
+
+  /**
+   * Load page bitmap (raw 1-bit data, skipping XTG header)
+   *
+   * @param pageIndex Page index (0-based)
+   * @param buffer Output buffer (caller allocated)
+   * @param bufferSize Buffer size
+   * @return Number of bytes read on success, 0 on failure
+   */
+  size_t loadPage(uint32_t pageIndex, uint8_t* buffer, size_t bufferSize);
+
+  /**
+   * Streaming page load
+   * Memory-efficient method that reads page data in chunks.
+   *
+   * @param pageIndex Page index
+   * @param callback Callback function to receive data chunks
+   * @param chunkSize Chunk size (default: 1024 bytes)
+   * @return Error code
+   */
+  XtcError loadPageStreaming(uint32_t pageIndex,
+                             std::function<void(const uint8_t* data, size_t size, size_t offset)> callback,
+                             size_t chunkSize = 1024);
+
+  // Get title from metadata
+  std::string getTitle() const { return m_title; }
+
+  // Validation
+  static bool isValidXtcFile(const char* filepath);
+
+  // Error information
+  XtcError getLastError() const { return m_lastError; }
+
+ private:
+  File m_file;
+  bool m_isOpen;
+  XtcHeader m_header;
+  std::vector<PageInfo> m_pageTable;
+  std::string m_title;
+  uint16_t m_defaultWidth;
+  uint16_t m_defaultHeight;
+  XtcError m_lastError;
+
+  // Internal helper functions
+  XtcError readHeader();
+  XtcError readPageTable();
+  XtcError readTitle();
+};
+
+}  // namespace xtc

lib/Xtc/Xtc/XtcTypes.h

@@ -0,0 +1,131 @@
+/**
+ * XtcTypes.h
+ *
+ * XTC file format type definitions
+ * XTC ebook support for CrossPoint Reader
+ *
+ * XTC is the native binary ebook format for XTeink X4 e-reader.
+ * It stores pre-rendered bitmap images per page.
+ *
+ * Format based on EPUB2XTC converter by Rafal-P-Mazur
+ */
+
+#pragma once
+
+#include <cstdint>
+
+namespace xtc {
+
+// XTC file magic numbers (little-endian)
+// "XTC\0" = 0x58, 0x54, 0x43, 0x00
+constexpr uint32_t XTC_MAGIC = 0x00435458;  // "XTC\0" in little-endian
+// "XTG\0" = 0x58, 0x54, 0x47, 0x00
+constexpr uint32_t XTG_MAGIC = 0x00475458;  // "XTG\0" for page data
+
+// XTeink X4 display resolution
+constexpr uint16_t DISPLAY_WIDTH = 480;
+constexpr uint16_t DISPLAY_HEIGHT = 800;
+
+// XTC file header (56 bytes)
+#pragma pack(push, 1)
+struct XtcHeader {
+  uint32_t magic;            // 0x00: Magic number "XTC\0" (0x00435458)
+  uint16_t version;          // 0x04: Format version (typically 1)
+  uint16_t pageCount;        // 0x06: Total page count
+  uint32_t flags;            // 0x08: Flags/reserved
+  uint32_t headerSize;       // 0x0C: Size of header section (typically 88)
+  uint32_t reserved1;        // 0x10: Reserved
+  uint32_t tocOffset;        // 0x14: TOC offset (0 if unused) - 4 bytes, not 8!
+  uint64_t pageTableOffset;  // 0x18: Page table offset
+  uint64_t dataOffset;       // 0x20: First page data offset
+  uint64_t reserved2;        // 0x28: Reserved
+  uint32_t titleOffset;      // 0x30: Title string offset
+  uint32_t padding;          // 0x34: Padding to 56 bytes
+};
+#pragma pack(pop)
+
+// Page table entry (16 bytes per page)
+#pragma pack(push, 1)
+struct PageTableEntry {
+  uint64_t dataOffset;  // 0x00: Absolute offset to page data
+  uint32_t dataSize;    // 0x08: Page data size in bytes
+  uint16_t width;       // 0x0C: Page width (480)
+  uint16_t height;      // 0x0E: Page height (800)
+};
+#pragma pack(pop)
+
+// XTG page data header (22 bytes)
+#pragma pack(push, 1)
+struct XtgPageHeader {
+  uint32_t magic;       // 0x00: Magic "XTG\0" (0x00475458)
+  uint16_t width;       // 0x04: Bitmap width
+  uint16_t height;      // 0x06: Bitmap height
+  uint16_t reserved1;   // 0x08: Reserved (0)
+  uint32_t bitmapSize;  // 0x0A: Bitmap data size = ((width+7)/8) * height
+  uint32_t reserved2;   // 0x0E: Reserved (0)
+  uint32_t reserved3;   // 0x12: Reserved (0)
+  // Followed by bitmap data at offset 0x16 (22)
+};
+#pragma pack(pop)
+
+// Page information (internal use)
+struct PageInfo {
+  uint64_t offset;  // File offset to page data
+  uint32_t size;    // Data size (bytes)
+  uint16_t width;   // Page width
+  uint16_t height;  // Page height
+};
+
+// Error codes
+enum class XtcError {
+  OK = 0,
+  FILE_NOT_FOUND,
+  INVALID_MAGIC,
+  INVALID_VERSION,
+  CORRUPTED_HEADER,
+  PAGE_OUT_OF_RANGE,
+  READ_ERROR,
+  WRITE_ERROR,
+  MEMORY_ERROR,
+  DECOMPRESSION_ERROR,
+};
+
+// Convert error code to string
+inline const char* errorToString(XtcError err) {
+  switch (err) {
+    case XtcError::OK:
+      return "OK";
+    case XtcError::FILE_NOT_FOUND:
+      return "File not found";
+    case XtcError::INVALID_MAGIC:
+      return "Invalid magic number";
+    case XtcError::INVALID_VERSION:
+      return "Unsupported version";
+    case XtcError::CORRUPTED_HEADER:
+      return "Corrupted header";
+    case XtcError::PAGE_OUT_OF_RANGE:
+      return "Page out of range";
+    case XtcError::READ_ERROR:
+      return "Read error";
+    case XtcError::WRITE_ERROR:
+      return "Write error";
+    case XtcError::MEMORY_ERROR:
+      return "Memory allocation error";
+    case XtcError::DECOMPRESSION_ERROR:
+      return "Decompression error";
+    default:
+      return "Unknown error";
+  }
+}
+
+/**
+ * Check if filename has XTC extension
+ */
+inline bool isXtcExtension(const char* filename) {
+  if (!filename) return false;
+  const char* ext = strrchr(filename, '.');
+  if (!ext) return false;
+  return (strcasecmp(ext, ".xtc") == 0 || strcasecmp(ext, ".xtg") == 0 || strcasecmp(ext, ".xth") == 0);
+}
+
+}  // namespace xtc

src/activities/boot_sleep/SleepActivity.cpp

@@ -4,6 +4,7 @@
 #include <FsHelpers.h>
 #include <GfxRenderer.h>
 #include <SD.h>
+#include <Xtc.h>
 
 #include <vector>
 
@@ -12,6 +13,15 @@
 #include "config.h"
 #include "images/CrossLarge.h"
 
+namespace {
+// Check if path has XTC extension
+bool isXtcFile(const std::string& path) {
+  if (path.length() < 4) return false;
+  std::string ext = path.substr(path.length() - 4);
+  return (ext == ".xtc" || ext == ".xtg" || ext == ".xth");
+}
+}  // namespace
+
 void SleepActivity::onEnter() {
   Activity::onEnter();
   renderPopup("Entering Sleep...");
@@ -176,19 +186,41 @@ void SleepActivity::renderCoverSleepScreen() const {
     return renderDefaultSleepScreen();
   }
 
-  Epub lastEpub(APP_STATE.openEpubPath, "/.crosspoint");
-  if (!lastEpub.load()) {
-    Serial.println("[SLP] Failed to load last epub");
-    return renderDefaultSleepScreen();
-  }
+  std::string coverBmpPath;
 
-  if (!lastEpub.generateCoverBmp()) {
-    Serial.println("[SLP] Failed to generate cover bmp");
-    return renderDefaultSleepScreen();
+  // Check if the current book is XTC or EPUB
+  if (isXtcFile(APP_STATE.openEpubPath)) {
+    // Handle XTC file
+    Xtc lastXtc(APP_STATE.openEpubPath, "/.crosspoint");
+    if (!lastXtc.load()) {
+      Serial.println("[SLP] Failed to load last XTC");
+      return renderDefaultSleepScreen();
+    }
+
+    if (!lastXtc.generateCoverBmp()) {
+      Serial.println("[SLP] Failed to generate XTC cover bmp");
+      return renderDefaultSleepScreen();
+    }
+
+    coverBmpPath = lastXtc.getCoverBmpPath();
+  } else {
+    // Handle EPUB file
+    Epub lastEpub(APP_STATE.openEpubPath, "/.crosspoint");
+    if (!lastEpub.load()) {
+      Serial.println("[SLP] Failed to load last epub");
+      return renderDefaultSleepScreen();
+    }
+
+    if (!lastEpub.generateCoverBmp()) {
+      Serial.println("[SLP] Failed to generate cover bmp");
+      return renderDefaultSleepScreen();
+    }
+
+    coverBmpPath = lastEpub.getCoverBmpPath();
   }
 
   File file;
-  if (FsHelpers::openFileForRead("SLP", lastEpub.getCoverBmpPath(), file)) {
+  if (FsHelpers::openFileForRead("SLP", coverBmpPath, file)) {
     Bitmap bitmap(file);
     if (bitmap.parseHeaders() == BmpReaderError::Ok) {
       renderBitmapSleepScreen(bitmap);

src/activities/reader/FileSelectionActivity.cpp

@@ -40,8 +40,14 @@ void FileSelectionActivity::loadFiles() {
 
     if (file.isDirectory()) {
       files.emplace_back(filename + "/");
-    } else if (filename.substr(filename.length() - 5) == ".epub") {
+    } else if (filename.length() >= 5 && filename.substr(filename.length() - 5) == ".epub") {
       files.emplace_back(filename);
+    } else if (filename.length() >= 4) {
+      // Check for XTC format extensions (.xtc, .xtg, .xth)
+      std::string ext = filename.substr(filename.length() - 4);
+      if (ext == ".xtc" || ext == ".xtg" || ext == ".xth") {
+        files.emplace_back(filename);
+      }
     }
     file.close();
   }
@@ -165,7 +171,7 @@ void FileSelectionActivity::render() const {
   renderer.drawButtonHints(UI_FONT_ID, "« Home", "", "", "");
 
   if (files.empty()) {
-    renderer.drawText(UI_FONT_ID, 20, 60, "No EPUBs found");
+    renderer.drawText(UI_FONT_ID, 20, 60, "No books found");
     renderer.displayBuffer();
     return;
   }

src/activities/reader/ReaderActivity.cpp

@@ -5,6 +5,8 @@
 #include "Epub.h"
 #include "EpubReaderActivity.h"
 #include "FileSelectionActivity.h"
+#include "Xtc.h"
+#include "XtcReaderActivity.h"
 #include "activities/util/FullScreenMessageActivity.h"
 
 std::string ReaderActivity::extractFolderPath(const std::string& filePath) {
@@ -15,6 +17,12 @@ std::string ReaderActivity::extractFolderPath(const std::string& filePath) {
   return filePath.substr(0, lastSlash);
 }
 
+bool ReaderActivity::isXtcFile(const std::string& path) {
+  if (path.length() < 4) return false;
+  std::string ext = path.substr(path.length() - 4);
+  return (ext == ".xtc" || ext == ".xtg" || ext == ".xth");
+}
+
 std::unique_ptr<Epub> ReaderActivity::loadEpub(const std::string& path) {
   if (!SD.exists(path.c_str())) {
     Serial.printf("[%lu] [   ] File does not exist: %s\n", millis(), path.c_str());
@@ -30,54 +38,102 @@ std::unique_ptr<Epub> ReaderActivity::loadEpub(const std::string& path) {
   return nullptr;
 }
 
-void ReaderActivity::onSelectEpubFile(const std::string& path) {
-  currentEpubPath = path;  // Track current book path
+std::unique_ptr<Xtc> ReaderActivity::loadXtc(const std::string& path) {
+  if (!SD.exists(path.c_str())) {
+    Serial.printf("[%lu] [   ] File does not exist: %s\n", millis(), path.c_str());
+    return nullptr;
+  }
+
+  auto xtc = std::unique_ptr<Xtc>(new Xtc(path, "/.crosspoint"));
+  if (xtc->load()) {
+    return xtc;
+  }
+
+  Serial.printf("[%lu] [   ] Failed to load XTC\n", millis());
+  return nullptr;
+}
+
+void ReaderActivity::onSelectBookFile(const std::string& path) {
+  currentBookPath = path;  // Track current book path
   exitActivity();
   enterNewActivity(new FullScreenMessageActivity(renderer, inputManager, "Loading..."));
 
-  auto epub = loadEpub(path);
-  if (epub) {
-    onGoToEpubReader(std::move(epub));
+  if (isXtcFile(path)) {
+    // Load XTC file
+    auto xtc = loadXtc(path);
+    if (xtc) {
+      onGoToXtcReader(std::move(xtc));
+    } else {
+      exitActivity();
+      enterNewActivity(new FullScreenMessageActivity(renderer, inputManager, "Failed to load XTC", REGULAR,
+                                                     EInkDisplay::HALF_REFRESH));
+      delay(2000);
+      onGoToFileSelection();
+    }
   } else {
-    exitActivity();
-    enterNewActivity(new FullScreenMessageActivity(renderer, inputManager, "Failed to load epub", REGULAR,
-                                                   EInkDisplay::HALF_REFRESH));
-    delay(2000);
-    onGoToFileSelection();
+    // Load EPUB file
+    auto epub = loadEpub(path);
+    if (epub) {
+      onGoToEpubReader(std::move(epub));
+    } else {
+      exitActivity();
+      enterNewActivity(new FullScreenMessageActivity(renderer, inputManager, "Failed to load epub", REGULAR,
+                                                     EInkDisplay::HALF_REFRESH));
+      delay(2000);
+      onGoToFileSelection();
+    }
   }
 }
 
-void ReaderActivity::onGoToFileSelection(const std::string& fromEpubPath) {
+void ReaderActivity::onGoToFileSelection(const std::string& fromBookPath) {
   exitActivity();
   // If coming from a book, start in that book's folder; otherwise start from root
-  const auto initialPath = fromEpubPath.empty() ? "/" : extractFolderPath(fromEpubPath);
+  const auto initialPath = fromBookPath.empty() ? "/" : extractFolderPath(fromBookPath);
   enterNewActivity(new FileSelectionActivity(
-      renderer, inputManager, [this](const std::string& path) { onSelectEpubFile(path); }, onGoBack, initialPath));
+      renderer, inputManager, [this](const std::string& path) { onSelectBookFile(path); }, onGoBack, initialPath));
 }
 
 void ReaderActivity::onGoToEpubReader(std::unique_ptr<Epub> epub) {
   const auto epubPath = epub->getPath();
-  currentEpubPath = epubPath;
+  currentBookPath = epubPath;
   exitActivity();
   enterNewActivity(new EpubReaderActivity(
       renderer, inputManager, std::move(epub), [this, epubPath] { onGoToFileSelection(epubPath); },
       [this] { onGoBack(); }));
 }
 
+void ReaderActivity::onGoToXtcReader(std::unique_ptr<Xtc> xtc) {
+  const auto xtcPath = xtc->getPath();
+  currentBookPath = xtcPath;
+  exitActivity();
+  enterNewActivity(new XtcReaderActivity(
+      renderer, inputManager, std::move(xtc), [this, xtcPath] { onGoToFileSelection(xtcPath); },
+      [this] { onGoBack(); }));
+}
+
 void ReaderActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
-  if (initialEpubPath.empty()) {
+  if (initialBookPath.empty()) {
     onGoToFileSelection();  // Start from root when entering via Browse
     return;
   }
 
-  currentEpubPath = initialEpubPath;
-  auto epub = loadEpub(initialEpubPath);
-  if (!epub) {
-    onGoBack();
-    return;
-  }
+  currentBookPath = initialBookPath;
 
-  onGoToEpubReader(std::move(epub));
+  if (isXtcFile(initialBookPath)) {
+    auto xtc = loadXtc(initialBookPath);
+    if (!xtc) {
+      onGoBack();
+      return;
+    }
+    onGoToXtcReader(std::move(xtc));
+  } else {
+    auto epub = loadEpub(initialBookPath);
+    if (!epub) {
+      onGoBack();
+      return;
+    }
+    onGoToEpubReader(std::move(epub));
+  }
 }

src/activities/reader/ReaderActivity.h

@@ -4,23 +4,27 @@
 #include "../ActivityWithSubactivity.h"
 
 class Epub;
+class Xtc;
 
 class ReaderActivity final : public ActivityWithSubactivity {
-  std::string initialEpubPath;
-  std::string currentEpubPath;  // Track current book path for navigation
+  std::string initialBookPath;
+  std::string currentBookPath;  // Track current book path for navigation
   const std::function<void()> onGoBack;
   static std::unique_ptr<Epub> loadEpub(const std::string& path);
+  static std::unique_ptr<Xtc> loadXtc(const std::string& path);
+  static bool isXtcFile(const std::string& path);
 
   static std::string extractFolderPath(const std::string& filePath);
-  void onSelectEpubFile(const std::string& path);
-  void onGoToFileSelection(const std::string& fromEpubPath = "");
+  void onSelectBookFile(const std::string& path);
+  void onGoToFileSelection(const std::string& fromBookPath = "");
   void onGoToEpubReader(std::unique_ptr<Epub> epub);
+  void onGoToXtcReader(std::unique_ptr<Xtc> xtc);
 
  public:
-  explicit ReaderActivity(GfxRenderer& renderer, InputManager& inputManager, std::string initialEpubPath,
+  explicit ReaderActivity(GfxRenderer& renderer, InputManager& inputManager, std::string initialBookPath,
                           const std::function<void()>& onGoBack)
       : ActivityWithSubactivity("Reader", renderer, inputManager),
-        initialEpubPath(std::move(initialEpubPath)),
+        initialBookPath(std::move(initialBookPath)),
         onGoBack(onGoBack) {}
   void onEnter() override;
 };

src/activities/reader/XtcReaderActivity.cpp

@@ -0,0 +1,311 @@
+/**
+ * XtcReaderActivity.cpp
+ *
+ * XTC ebook reader activity implementation
+ * Displays pre-rendered XTC pages on e-ink display
+ */
+
+#include "XtcReaderActivity.h"
+
+#include <FsHelpers.h>
+#include <GfxRenderer.h>
+#include <InputManager.h>
+
+#include "Battery.h"
+#include "CrossPointSettings.h"
+#include "CrossPointState.h"
+#include "config.h"
+
+namespace {
+constexpr int pagesPerRefresh = 15;
+constexpr unsigned long skipPageMs = 700;
+constexpr unsigned long goHomeMs = 1000;
+constexpr int statusBarHeight = 24;
+constexpr int marginLeft = 10;
+constexpr int marginRight = 10;
+}  // namespace
+
+void XtcReaderActivity::taskTrampoline(void* param) {
+  auto* self = static_cast<XtcReaderActivity*>(param);
+  self->displayTaskLoop();
+}
+
+void XtcReaderActivity::onEnter() {
+  Activity::onEnter();
+
+  if (!xtc) {
+    return;
+  }
+
+  renderingMutex = xSemaphoreCreateMutex();
+
+  xtc->setupCacheDir();
+
+  // Load saved progress
+  loadProgress();
+
+  // Save current XTC as last opened book
+  APP_STATE.openEpubPath = xtc->getPath();
+  APP_STATE.saveToFile();
+
+  // Trigger first update
+  updateRequired = true;
+
+  xTaskCreate(&XtcReaderActivity::taskTrampoline, "XtcReaderActivityTask",
+              4096,               // Stack size (smaller than EPUB since no parsing needed)
+              this,               // Parameters
+              1,                  // Priority
+              &displayTaskHandle  // Task handle
+  );
+}
+
+void XtcReaderActivity::onExit() {
+  Activity::onExit();
+
+  // Wait until not rendering to delete task
+  xSemaphoreTake(renderingMutex, portMAX_DELAY);
+  if (displayTaskHandle) {
+    vTaskDelete(displayTaskHandle);
+    displayTaskHandle = nullptr;
+  }
+  vSemaphoreDelete(renderingMutex);
+  renderingMutex = nullptr;
+  xtc.reset();
+}
+
+void XtcReaderActivity::loop() {
+  // Long press BACK (1s+) goes directly to home
+  if (inputManager.isPressed(InputManager::BTN_BACK) && inputManager.getHeldTime() >= goHomeMs) {
+    onGoHome();
+    return;
+  }
+
+  // Short press BACK goes to file selection
+  if (inputManager.wasReleased(InputManager::BTN_BACK) && inputManager.getHeldTime() < goHomeMs) {
+    onGoBack();
+    return;
+  }
+
+  const bool prevReleased =
+      inputManager.wasReleased(InputManager::BTN_UP) || inputManager.wasReleased(InputManager::BTN_LEFT);
+  const bool nextReleased =
+      inputManager.wasReleased(InputManager::BTN_DOWN) || inputManager.wasReleased(InputManager::BTN_RIGHT);
+
+  if (!prevReleased && !nextReleased) {
+    return;
+  }
+
+  // Handle end of book
+  if (currentPage >= xtc->getPageCount()) {
+    currentPage = xtc->getPageCount() - 1;
+    updateRequired = true;
+    return;
+  }
+
+  const bool skipPages = inputManager.getHeldTime() > skipPageMs;
+  const int skipAmount = skipPages ? 10 : 1;
+
+  if (prevReleased) {
+    if (currentPage >= static_cast<uint32_t>(skipAmount)) {
+      currentPage -= skipAmount;
+    } else {
+      currentPage = 0;
+    }
+    updateRequired = true;
+  } else if (nextReleased) {
+    currentPage += skipAmount;
+    if (currentPage >= xtc->getPageCount()) {
+      currentPage = xtc->getPageCount();  // Allow showing "End of book"
+    }
+    updateRequired = true;
+  }
+}
+
+void XtcReaderActivity::displayTaskLoop() {
+  while (true) {
+    if (updateRequired) {
+      updateRequired = false;
+      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+      renderScreen();
+      xSemaphoreGive(renderingMutex);
+    }
+    vTaskDelay(10 / portTICK_PERIOD_MS);
+  }
+}
+
+void XtcReaderActivity::renderScreen() {
+  if (!xtc) {
+    return;
+  }
+
+  // Bounds check
+  if (currentPage >= xtc->getPageCount()) {
+    // Show end of book screen
+    renderer.clearScreen();
+    renderer.drawCenteredText(UI_FONT_ID, 300, "End of book", true, BOLD);
+    renderer.displayBuffer();
+    return;
+  }
+
+  renderPage();
+  saveProgress();
+}
+
+void XtcReaderActivity::renderPage() {
+  const uint16_t pageWidth = xtc->getPageWidth();
+  const uint16_t pageHeight = xtc->getPageHeight();
+
+  // Calculate buffer size for one page (XTC is always 1-bit monochrome)
+  const size_t pageBufferSize = ((pageWidth + 7) / 8) * pageHeight;
+
+  // Allocate page buffer
+  uint8_t* pageBuffer = static_cast<uint8_t*>(malloc(pageBufferSize));
+  if (!pageBuffer) {
+    Serial.printf("[%lu] [XTR] Failed to allocate page buffer (%lu bytes)\n", millis(), pageBufferSize);
+    renderer.clearScreen();
+    renderer.drawCenteredText(UI_FONT_ID, 300, "Memory error", true, BOLD);
+    renderer.displayBuffer();
+    return;
+  }
+
+  // Load page data
+  size_t bytesRead = xtc->loadPage(currentPage, pageBuffer, pageBufferSize);
+  if (bytesRead == 0) {
+    Serial.printf("[%lu] [XTR] Failed to load page %lu\n", millis(), currentPage);
+    free(pageBuffer);
+    renderer.clearScreen();
+    renderer.drawCenteredText(UI_FONT_ID, 300, "Page load error", true, BOLD);
+    renderer.displayBuffer();
+    return;
+  }
+
+  // Clear screen first
+  renderer.clearScreen();
+
+  // Copy page bitmap using GfxRenderer's drawPixel
+  // XTC stores 1-bit packed data in portrait (480x800) format
+  const size_t srcRowBytes = (pageWidth + 7) / 8;  // 60 bytes for 480 width
+
+  // XTC pages are pre-rendered with status bar included, so render full page
+  const uint16_t maxSrcY = pageHeight;
+
+  for (uint16_t srcY = 0; srcY < maxSrcY; srcY++) {
+    const size_t srcRowStart = srcY * srcRowBytes;
+
+    for (uint16_t srcX = 0; srcX < pageWidth; srcX++) {
+      // Read source pixel (MSB first, bit 7 = leftmost pixel)
+      const size_t srcByte = srcRowStart + srcX / 8;
+      const size_t srcBit = 7 - (srcX % 8);
+      const bool isBlack = !((pageBuffer[srcByte] >> srcBit) & 1);  // XTC: 0 = black, 1 = white
+
+      // Use GfxRenderer's drawPixel with logical portrait coordinates
+      // drawPixel(x, y, state) where state=true draws black
+      if (isBlack) {
+        renderer.drawPixel(srcX, srcY, true);
+      }
+      // White pixels are already cleared by clearScreen()
+    }
+  }
+
+  free(pageBuffer);
+
+  // XTC pages already have status bar pre-rendered, no need to add our own
+
+  // Display with appropriate refresh
+  if (pagesUntilFullRefresh <= 1) {
+    renderer.displayBuffer(EInkDisplay::HALF_REFRESH);
+    pagesUntilFullRefresh = pagesPerRefresh;
+  } else {
+    renderer.displayBuffer();
+    pagesUntilFullRefresh--;
+  }
+
+  Serial.printf("[%lu] [XTR] Rendered page %lu/%lu\n", millis(), currentPage + 1, xtc->getPageCount());
+}
+
+void XtcReaderActivity::renderStatusBar() const {
+  const int screenWidth = GfxRenderer::getScreenWidth();
+  const int screenHeight = GfxRenderer::getScreenHeight();
+  constexpr int textY = 776;
+
+  // Calculate progress
+  const uint8_t progress = xtc->calculateProgress(currentPage);
+
+  // Right aligned: page number and progress
+  const std::string progressText = std::to_string(currentPage + 1) + "/" + std::to_string(xtc->getPageCount()) + "  " +
+                                   std::to_string(progress) + "%";
+  const int progressTextWidth = renderer.getTextWidth(SMALL_FONT_ID, progressText.c_str());
+  renderer.drawText(SMALL_FONT_ID, screenWidth - marginRight - progressTextWidth, textY, progressText.c_str());
+
+  // Left aligned: battery
+  const uint16_t percentage = battery.readPercentage();
+  const std::string percentageText = std::to_string(percentage) + "%";
+  const int percentageTextWidth = renderer.getTextWidth(SMALL_FONT_ID, percentageText.c_str());
+  renderer.drawText(SMALL_FONT_ID, 20 + marginLeft, textY, percentageText.c_str());
+
+  // Battery icon
+  constexpr int batteryWidth = 15;
+  constexpr int batteryHeight = 10;
+  constexpr int x = marginLeft;
+  constexpr int y = 783;
+
+  // Battery outline
+  renderer.drawLine(x, y, x + batteryWidth - 4, y);
+  renderer.drawLine(x, y + batteryHeight - 1, x + batteryWidth - 4, y + batteryHeight - 1);
+  renderer.drawLine(x, y, x, y + batteryHeight - 1);
+  renderer.drawLine(x + batteryWidth - 4, y, x + batteryWidth - 4, y + batteryHeight - 1);
+  renderer.drawLine(x + batteryWidth - 3, y + 2, x + batteryWidth - 1, y + 2);
+  renderer.drawLine(x + batteryWidth - 3, y + batteryHeight - 3, x + batteryWidth - 1, y + batteryHeight - 3);
+  renderer.drawLine(x + batteryWidth - 1, y + 2, x + batteryWidth - 1, y + batteryHeight - 3);
+
+  // Battery fill
+  int filledWidth = percentage * (batteryWidth - 5) / 100 + 1;
+  if (filledWidth > batteryWidth - 5) {
+    filledWidth = batteryWidth - 5;
+  }
+  renderer.fillRect(x + 1, y + 1, filledWidth, batteryHeight - 2);
+
+  // Center: book title
+  const int titleMarginLeft = 20 + percentageTextWidth + 30 + marginLeft;
+  const int titleMarginRight = progressTextWidth + 30 + marginRight;
+  const int availableTextWidth = screenWidth - titleMarginLeft - titleMarginRight;
+
+  std::string title = xtc->getTitle();
+  int titleWidth = renderer.getTextWidth(SMALL_FONT_ID, title.c_str());
+  while (titleWidth > availableTextWidth && title.length() > 11) {
+    title.replace(title.length() - 8, 8, "...");
+    titleWidth = renderer.getTextWidth(SMALL_FONT_ID, title.c_str());
+  }
+
+  renderer.drawText(SMALL_FONT_ID, titleMarginLeft + (availableTextWidth - titleWidth) / 2, textY, title.c_str());
+}
+
+void XtcReaderActivity::saveProgress() const {
+  File f;
+  if (FsHelpers::openFileForWrite("XTR", xtc->getCachePath() + "/progress.bin", f)) {
+    uint8_t data[4];
+    data[0] = currentPage & 0xFF;
+    data[1] = (currentPage >> 8) & 0xFF;
+    data[2] = (currentPage >> 16) & 0xFF;
+    data[3] = (currentPage >> 24) & 0xFF;
+    f.write(data, 4);
+    f.close();
+  }
+}
+
+void XtcReaderActivity::loadProgress() {
+  File f;
+  if (FsHelpers::openFileForRead("XTR", xtc->getCachePath() + "/progress.bin", f)) {
+    uint8_t data[4];
+    if (f.read(data, 4) == 4) {
+      currentPage = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
+      Serial.printf("[%lu] [XTR] Loaded progress: page %lu\n", millis(), currentPage);
+
+      // Validate page number
+      if (currentPage >= xtc->getPageCount()) {
+        currentPage = 0;
+      }
+    }
+    f.close();
+  }
+}

src/activities/reader/XtcReaderActivity.h

@@ -0,0 +1,42 @@
+/**
+ * XtcReaderActivity.h
+ *
+ * XTC ebook reader activity for CrossPoint Reader
+ * Displays pre-rendered XTC pages on e-ink display
+ */
+
+#pragma once
+
+#include <Xtc.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/semphr.h>
+#include <freertos/task.h>
+
+#include "activities/Activity.h"
+
+class XtcReaderActivity final : public Activity {
+  std::shared_ptr<Xtc> xtc;
+  TaskHandle_t displayTaskHandle = nullptr;
+  SemaphoreHandle_t renderingMutex = nullptr;
+  uint32_t currentPage = 0;
+  int pagesUntilFullRefresh = 0;
+  bool updateRequired = false;
+  const std::function<void()> onGoBack;
+  const std::function<void()> onGoHome;
+
+  static void taskTrampoline(void* param);
+  [[noreturn]] void displayTaskLoop();
+  void renderScreen();
+  void renderPage();
+  void renderStatusBar() const;
+  void saveProgress() const;
+  void loadProgress();
+
+ public:
+  explicit XtcReaderActivity(GfxRenderer& renderer, InputManager& inputManager, std::unique_ptr<Xtc> xtc,
+                             const std::function<void()>& onGoBack, const std::function<void()>& onGoHome)
+      : Activity("XtcReader", renderer, inputManager), xtc(std::move(xtc)), onGoBack(onGoBack), onGoHome(onGoHome) {}
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+};