feat: Implement bookmark functionality for epub reader

Replace bookmark stubs with full add/remove/navigate implementation:

- BookmarkStore: per-book binary persistence on SD card with v2 format
  supporting text snippets (backward-compatible with v1)
- Visual bookmark ribbon indicator drawn on bookmarked pages via fillPolygon
- Reader menu dynamically shows Add/Remove Bookmark based on current page state
- Bookmark selection activity with chapter name, first sentence snippet, and
  page number display; long-press to delete with confirmation
- Go to Bookmark falls back to Table of Contents when no bookmarks exist
- Smart snippet extraction: skips partial sentences (lowercase first word)
  to capture the first full sentence on the page
- Label truncation reserves space for page suffix so it's never cut off
- Half refresh forced on menu exit to clear popup/menu artifacts

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/reader/EpubReaderActivity.cpp

@@ -7,6 +7,7 @@
 
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
+#include "EpubReaderBookmarkSelectionActivity.h"
 #include "EpubReaderChapterSelectionActivity.h"
 #include "EpubReaderPercentSelectionActivity.h"
 #include "KOReaderCredentialStore.h"
@@ -15,6 +16,7 @@
 #include "RecentBooksStore.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
+#include "util/BookmarkStore.h"
 #include "util/Dictionary.h"
 #include "util/LookupHistory.h"
 
@@ -235,10 +237,13 @@ void EpubReaderActivity::loop() {
     }
     const int bookProgressPercent = clampPercent(static_cast<int>(bookProgress + 0.5f));
     const bool hasDictionary = Dictionary::exists();
+    const bool isBookmarked = BookmarkStore::hasBookmark(
+        epub->getCachePath(), currentSpineIndex, section ? section->currentPage : 0);
     exitActivity();
     enterNewActivity(new EpubReaderMenuActivity(
         this->renderer, this->mappedInput, epub->getTitle(), currentPage, totalPages, bookProgressPercent,
-        SETTINGS.orientation, hasDictionary, [this](const uint8_t orientation) { onReaderMenuBack(orientation); },
+        SETTINGS.orientation, hasDictionary, isBookmarked,
+        [this](const uint8_t orientation) { onReaderMenuBack(orientation); },
         [this](EpubReaderMenuActivity::MenuAction action) { onReaderMenuConfirm(action); }));
     xSemaphoreGive(renderingMutex);
   }
@@ -332,6 +337,8 @@ void EpubReaderActivity::onReaderMenuBack(const uint8_t orientation) {
   // Apply the user-selected orientation when the menu is dismissed.
   // This ensures the menu can be navigated without immediately rotating the screen.
   applyOrientation(orientation);
+  // Force a half refresh on the next render to clear menu/popup artifacts
+  pagesUntilFullRefresh = 1;
   updateRequired = true;
 }
 
@@ -400,21 +407,151 @@ void EpubReaderActivity::jumpToPercent(int percent) {
 void EpubReaderActivity::onReaderMenuConfirm(EpubReaderMenuActivity::MenuAction action) {
   switch (action) {
     case EpubReaderMenuActivity::MenuAction::ADD_BOOKMARK: {
-      // Stub — bookmark feature coming soon
+      const int page = section ? section->currentPage : 0;
+
+      // Extract first full sentence from the current page for the bookmark snippet.
+      // If the first word is lowercase, the page starts mid-sentence — skip to the
+      // next sentence boundary and start collecting from there.
+      std::string snippet;
+      if (section) {
+        auto p = section->loadPageFromSectionFile();
+        if (p) {
+          // Gather all words on the page into a flat list for easier traversal
+          std::vector<std::string> allWords;
+          for (const auto& element : p->elements) {
+            const auto* line = static_cast<const PageLine*>(element.get());
+            if (!line) continue;
+            const auto& block = line->getBlock();
+            if (!block) continue;
+            for (const auto& word : block->getWords()) {
+              allWords.push_back(word);
+            }
+          }
+
+          if (!allWords.empty()) {
+            size_t startIdx = 0;
+
+            // Check if the first word starts with a lowercase letter (mid-sentence)
+            const char firstChar = allWords[0].empty() ? '\0' : allWords[0][0];
+            if (firstChar >= 'a' && firstChar <= 'z') {
+              // Skip past the end of this partial sentence
+              for (size_t i = 0; i < allWords.size(); i++) {
+                if (!allWords[i].empty()) {
+                  char last = allWords[i].back();
+                  if (last == '.' || last == '!' || last == '?' || last == ':') {
+                    startIdx = i + 1;
+                    break;
+                  }
+                }
+              }
+              // If no sentence boundary found, fall back to using everything from the start
+              if (startIdx >= allWords.size()) {
+                startIdx = 0;
+              }
+            }
+
+            // Collect words from startIdx until the next sentence boundary
+            for (size_t i = startIdx; i < allWords.size(); i++) {
+              if (!snippet.empty()) snippet += " ";
+              snippet += allWords[i];
+              if (!allWords[i].empty()) {
+                char last = allWords[i].back();
+                if (last == '.' || last == '!' || last == '?' || last == ':') {
+                  break;
+                }
+              }
+            }
+          }
+        }
+      }
+
+      BookmarkStore::addBookmark(epub->getCachePath(), currentSpineIndex, page, snippet);
       xSemaphoreTake(renderingMutex, portMAX_DELAY);
-      GUI.drawPopup(renderer, "Coming soon");
+      GUI.drawPopup(renderer, "Bookmark added");
       renderer.displayBuffer(HalDisplay::FAST_REFRESH);
       xSemaphoreGive(renderingMutex);
-      vTaskDelay(1500 / portTICK_PERIOD_MS);
+      vTaskDelay(750 / portTICK_PERIOD_MS);
+      // Exit the menu and return to reading — the bookmark indicator will show on re-render,
+      // and next menu open will reflect the updated state.
+      exitActivity();
+      pagesUntilFullRefresh = 1;
+      updateRequired = true;
+      break;
+    }
+    case EpubReaderMenuActivity::MenuAction::REMOVE_BOOKMARK: {
+      const int page = section ? section->currentPage : 0;
+      BookmarkStore::removeBookmark(epub->getCachePath(), currentSpineIndex, page);
+      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+      GUI.drawPopup(renderer, "Bookmark removed");
+      renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+      xSemaphoreGive(renderingMutex);
+      vTaskDelay(750 / portTICK_PERIOD_MS);
+      exitActivity();
+      pagesUntilFullRefresh = 1;
+      updateRequired = true;
       break;
     }
     case EpubReaderMenuActivity::MenuAction::GO_TO_BOOKMARK: {
-      // Stub — bookmark feature coming soon
+      auto bookmarks = BookmarkStore::load(epub->getCachePath());
+
+      if (bookmarks.empty()) {
+        // No bookmarks: fall back to Table of Contents if available, otherwise go back
+        if (epub->getTocItemsCount() > 0) {
+          const int currentP = section ? section->currentPage : 0;
+          const int totalP = section ? section->pageCount : 0;
+          const int spineIdx = currentSpineIndex;
+          const std::string path = epub->getPath();
+
+          xSemaphoreTake(renderingMutex, portMAX_DELAY);
+          exitActivity();
+          enterNewActivity(new EpubReaderChapterSelectionActivity(
+              this->renderer, this->mappedInput, epub, path, spineIdx, currentP, totalP,
+              [this] {
+                exitActivity();
+                updateRequired = true;
+              },
+              [this](const int newSpineIndex) {
+                if (currentSpineIndex != newSpineIndex) {
+                  currentSpineIndex = newSpineIndex;
+                  nextPageNumber = 0;
+                  section.reset();
+                }
+                exitActivity();
+                updateRequired = true;
+              },
+              [this](const int newSpineIndex, const int newPage) {
+                if (currentSpineIndex != newSpineIndex || (section && section->currentPage != newPage)) {
+                  currentSpineIndex = newSpineIndex;
+                  nextPageNumber = newPage;
+                  section.reset();
+                }
+                exitActivity();
+                updateRequired = true;
+              }));
+          xSemaphoreGive(renderingMutex);
+        }
+        // If no TOC either, just return to reader (menu already closed by callback)
+        break;
+      }
+
       xSemaphoreTake(renderingMutex, portMAX_DELAY);
-      GUI.drawPopup(renderer, "Coming soon");
-      renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+      exitActivity();
+      enterNewActivity(new EpubReaderBookmarkSelectionActivity(
+          this->renderer, this->mappedInput, epub, std::move(bookmarks), epub->getCachePath(),
+          [this] {
+            exitActivity();
+            updateRequired = true;
+          },
+          [this](const int newSpineIndex, const int newPage) {
+            if (currentSpineIndex != newSpineIndex || (section && section->currentPage != newPage)) {
+              currentSpineIndex = newSpineIndex;
+              nextPageNumber = newPage;
+              section.reset();
+            }
+            exitActivity();
+            updateRequired = true;
+          }));
       xSemaphoreGive(renderingMutex);
-      vTaskDelay(1500 / portTICK_PERIOD_MS);
       break;
     }
     case EpubReaderMenuActivity::MenuAction::DELETE_DICT_CACHE: {
@@ -832,6 +969,22 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
                                         const int orientedMarginRight, const int orientedMarginBottom,
                                         const int orientedMarginLeft) {
   page->render(renderer, SETTINGS.getReaderFontId(), orientedMarginLeft, orientedMarginTop);
+
+  // Draw bookmark ribbon indicator in top-right corner if current page is bookmarked
+  if (section && BookmarkStore::hasBookmark(epub->getCachePath(), currentSpineIndex, section->currentPage)) {
+    const int screenWidth = renderer.getScreenWidth();
+    const int bkWidth = 12;
+    const int bkHeight = 22;
+    const int bkX = screenWidth - orientedMarginRight - bkWidth + 2;
+    const int bkY = 0;
+    const int notchDepth = bkHeight / 3;
+    const int centerX = bkX + bkWidth / 2;
+
+    const int xPoints[5] = {bkX, bkX + bkWidth, bkX + bkWidth, centerX, bkX};
+    const int yPoints[5] = {bkY, bkY, bkY + bkHeight, bkY + bkHeight - notchDepth, bkY + bkHeight};
+    renderer.fillPolygon(xPoints, yPoints, 5, true);
+  }
+
   renderStatusBar(orientedMarginRight, orientedMarginBottom, orientedMarginLeft);
   if (pagesUntilFullRefresh <= 1) {
     renderer.displayBuffer(HalDisplay::HALF_REFRESH);

src/activities/reader/EpubReaderBookmarkSelectionActivity.cpp

@@ -0,0 +1,262 @@
+#include "EpubReaderBookmarkSelectionActivity.h"
+
+#include <GfxRenderer.h>
+
+#include "MappedInputManager.h"
+#include "components/UITheme.h"
+#include "fontIds.h"
+
+int EpubReaderBookmarkSelectionActivity::getTotalItems() const { return static_cast<int>(bookmarks.size()); }
+
+int EpubReaderBookmarkSelectionActivity::getPageItems() const {
+  constexpr int lineHeight = 30;
+
+  const int screenHeight = renderer.getScreenHeight();
+  const auto orientation = renderer.getOrientation();
+  const bool isPortraitInverted = orientation == GfxRenderer::Orientation::PortraitInverted;
+  const int hintGutterHeight = isPortraitInverted ? 50 : 0;
+  const int startY = 60 + hintGutterHeight;
+  const int availableHeight = screenHeight - startY - lineHeight;
+  return std::max(1, availableHeight / lineHeight);
+}
+
+std::string EpubReaderBookmarkSelectionActivity::getBookmarkPrefix(const Bookmark& bookmark) const {
+  std::string label;
+  if (epub) {
+    const int tocIndex = epub->getTocIndexForSpineIndex(bookmark.spineIndex);
+    if (tocIndex >= 0 && tocIndex < epub->getTocItemsCount()) {
+      label = epub->getTocItem(tocIndex).title;
+    } else {
+      label = "Chapter " + std::to_string(bookmark.spineIndex + 1);
+    }
+  } else {
+    label = "Chapter " + std::to_string(bookmark.spineIndex + 1);
+  }
+  if (!bookmark.snippet.empty()) {
+    label += " - " + bookmark.snippet;
+  }
+  return label;
+}
+
+std::string EpubReaderBookmarkSelectionActivity::getPageSuffix(const Bookmark& bookmark) {
+  return " - Page " + std::to_string(bookmark.pageNumber + 1);
+}
+
+void EpubReaderBookmarkSelectionActivity::taskTrampoline(void* param) {
+  auto* self = static_cast<EpubReaderBookmarkSelectionActivity*>(param);
+  self->displayTaskLoop();
+}
+
+void EpubReaderBookmarkSelectionActivity::onEnter() {
+  ActivityWithSubactivity::onEnter();
+
+  renderingMutex = xSemaphoreCreateMutex();
+
+  // Trigger first update
+  updateRequired = true;
+  xTaskCreate(&EpubReaderBookmarkSelectionActivity::taskTrampoline, "BookmarkSelTask",
+              4096,               // Stack size
+              this,               // Parameters
+              1,                  // Priority
+              &displayTaskHandle  // Task handle
+  );
+}
+
+void EpubReaderBookmarkSelectionActivity::onExit() {
+  ActivityWithSubactivity::onExit();
+
+  xSemaphoreTake(renderingMutex, portMAX_DELAY);
+  if (displayTaskHandle) {
+    vTaskDelete(displayTaskHandle);
+    displayTaskHandle = nullptr;
+  }
+  vSemaphoreDelete(renderingMutex);
+  renderingMutex = nullptr;
+}
+
+void EpubReaderBookmarkSelectionActivity::loop() {
+  if (subActivity) {
+    subActivity->loop();
+    return;
+  }
+
+  const int totalItems = getTotalItems();
+
+  if (totalItems == 0) {
+    // All bookmarks deleted, go back
+    if (mappedInput.wasReleased(MappedInputManager::Button::Back) ||
+        mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+      onGoBack();
+    }
+    return;
+  }
+
+  // Delete confirmation mode: wait for confirm (delete) or back (cancel)
+  if (deleteConfirmMode) {
+    if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+      if (ignoreNextConfirmRelease) {
+        // Ignore the release from the initial long press
+        ignoreNextConfirmRelease = false;
+      } else {
+        // Confirm delete
+        BookmarkStore::removeBookmark(cachePath, bookmarks[pendingDeleteIndex].spineIndex,
+                                      bookmarks[pendingDeleteIndex].pageNumber);
+        bookmarks.erase(bookmarks.begin() + pendingDeleteIndex);
+        if (selectorIndex >= static_cast<int>(bookmarks.size())) {
+          selectorIndex = std::max(0, static_cast<int>(bookmarks.size()) - 1);
+        }
+        deleteConfirmMode = false;
+        updateRequired = true;
+      }
+    }
+    if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
+      deleteConfirmMode = false;
+      ignoreNextConfirmRelease = false;
+      updateRequired = true;
+    }
+    return;
+  }
+
+  // Detect long press on Confirm to trigger delete
+  constexpr unsigned long DELETE_HOLD_MS = 700;
+  if (mappedInput.isPressed(MappedInputManager::Button::Confirm) && mappedInput.getHeldTime() >= DELETE_HOLD_MS) {
+    if (totalItems > 0 && selectorIndex >= 0 && selectorIndex < totalItems) {
+      deleteConfirmMode = true;
+      ignoreNextConfirmRelease = true;
+      pendingDeleteIndex = selectorIndex;
+      updateRequired = true;
+    }
+    return;
+  }
+
+  const int pageItems = getPageItems();
+
+  if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+    if (selectorIndex >= 0 && selectorIndex < totalItems) {
+      const auto& b = bookmarks[selectorIndex];
+      onSelectBookmark(b.spineIndex, b.pageNumber);
+    } else {
+      onGoBack();
+    }
+  } else if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
+    onGoBack();
+  }
+
+  buttonNavigator.onNextRelease([this, totalItems] {
+    selectorIndex = ButtonNavigator::nextIndex(selectorIndex, totalItems);
+    updateRequired = true;
+  });
+
+  buttonNavigator.onPreviousRelease([this, totalItems] {
+    selectorIndex = ButtonNavigator::previousIndex(selectorIndex, totalItems);
+    updateRequired = true;
+  });
+
+  buttonNavigator.onNextContinuous([this, totalItems, pageItems] {
+    selectorIndex = ButtonNavigator::nextPageIndex(selectorIndex, totalItems, pageItems);
+    updateRequired = true;
+  });
+
+  buttonNavigator.onPreviousContinuous([this, totalItems, pageItems] {
+    selectorIndex = ButtonNavigator::previousPageIndex(selectorIndex, totalItems, pageItems);
+    updateRequired = true;
+  });
+}
+
+void EpubReaderBookmarkSelectionActivity::displayTaskLoop() {
+  while (true) {
+    if (updateRequired && !subActivity) {
+      updateRequired = false;
+      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+      renderScreen();
+      xSemaphoreGive(renderingMutex);
+    }
+    vTaskDelay(10 / portTICK_PERIOD_MS);
+  }
+}
+
+void EpubReaderBookmarkSelectionActivity::renderScreen() {
+  renderer.clearScreen();
+
+  const auto pageWidth = renderer.getScreenWidth();
+  const auto orientation = renderer.getOrientation();
+  const bool isLandscapeCw = orientation == GfxRenderer::Orientation::LandscapeClockwise;
+  const bool isLandscapeCcw = orientation == GfxRenderer::Orientation::LandscapeCounterClockwise;
+  const bool isPortraitInverted = orientation == GfxRenderer::Orientation::PortraitInverted;
+  const int hintGutterWidth = (isLandscapeCw || isLandscapeCcw) ? 30 : 0;
+  const int contentX = isLandscapeCw ? hintGutterWidth : 0;
+  const int contentWidth = pageWidth - hintGutterWidth;
+  const int hintGutterHeight = isPortraitInverted ? 50 : 0;
+  const int contentY = hintGutterHeight;
+  const int pageItems = getPageItems();
+  const int totalItems = getTotalItems();
+
+  // Title
+  const int titleX =
+      contentX + (contentWidth - renderer.getTextWidth(UI_12_FONT_ID, "Go to Bookmark", EpdFontFamily::BOLD)) / 2;
+  renderer.drawText(UI_12_FONT_ID, titleX, 15 + contentY, "Go to Bookmark", true, EpdFontFamily::BOLD);
+
+  if (totalItems == 0) {
+    renderer.drawCenteredText(UI_10_FONT_ID, 100 + contentY, "No bookmarks", true);
+  } else {
+    const auto pageStartIndex = selectorIndex / pageItems * pageItems;
+    renderer.fillRect(contentX, 60 + contentY + (selectorIndex % pageItems) * 30 - 2, contentWidth - 1, 30);
+
+    const int maxLabelWidth = contentWidth - 40 - contentX - 20;
+
+    for (int i = 0; i < pageItems; i++) {
+      int itemIndex = pageStartIndex + i;
+      if (itemIndex >= totalItems) break;
+      const int displayY = 60 + contentY + i * 30;
+      const bool isSelected = (itemIndex == selectorIndex);
+
+      const std::string suffix = getPageSuffix(bookmarks[itemIndex]);
+      const int suffixWidth = renderer.getTextWidth(UI_10_FONT_ID, suffix.c_str());
+
+      // Truncate the prefix (chapter + snippet) to leave room for the page suffix
+      const std::string prefix = getBookmarkPrefix(bookmarks[itemIndex]);
+      const std::string truncatedPrefix =
+          renderer.truncatedText(UI_10_FONT_ID, prefix.c_str(), maxLabelWidth - suffixWidth);
+
+      const std::string label = truncatedPrefix + suffix;
+
+      renderer.drawText(UI_10_FONT_ID, contentX + 20, displayY, label.c_str(), !isSelected);
+    }
+  }
+
+  if (deleteConfirmMode && pendingDeleteIndex < static_cast<int>(bookmarks.size())) {
+    // Draw delete confirmation overlay
+    const std::string suffix = getPageSuffix(bookmarks[pendingDeleteIndex]);
+    std::string msg = "Delete bookmark" + suffix + "?";
+
+    constexpr int margin = 15;
+    constexpr int popupY = 200;
+    const int textWidth = renderer.getTextWidth(UI_12_FONT_ID, msg.c_str(), EpdFontFamily::BOLD);
+    const int textHeight = renderer.getLineHeight(UI_12_FONT_ID);
+    const int w = textWidth + margin * 2;
+    const int h = textHeight + margin * 2;
+    const int x = (renderer.getScreenWidth() - w) / 2;
+
+    renderer.fillRect(x - 2, popupY - 2, w + 4, h + 4, true);
+    renderer.fillRect(x, popupY, w, h, false);
+
+    const int textX = x + (w - textWidth) / 2;
+    const int textY = popupY + margin - 2;
+    renderer.drawText(UI_12_FONT_ID, textX, textY, msg.c_str(), true, EpdFontFamily::BOLD);
+
+    const auto labels = mappedInput.mapLabels("Cancel", "Delete", "", "");
+    GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
+  } else {
+    if (!bookmarks.empty()) {
+      const char* deleteHint = "Hold select to delete";
+      const int hintWidth = renderer.getTextWidth(SMALL_FONT_ID, deleteHint);
+      renderer.drawText(SMALL_FONT_ID, (renderer.getScreenWidth() - hintWidth) / 2,
+                        renderer.getScreenHeight() - 70, deleteHint);
+    }
+
+    const auto labels = mappedInput.mapLabels("\xC2\xAB Back", "Select", "Up", "Down");
+    GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
+  }
+
+  renderer.displayBuffer();
+}

src/activities/reader/EpubReaderBookmarkSelectionActivity.h

@@ -0,0 +1,60 @@
+#pragma once
+#include <Epub.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/semphr.h>
+#include <freertos/task.h>
+
+#include <memory>
+#include <vector>
+
+#include "../ActivityWithSubactivity.h"
+#include "util/BookmarkStore.h"
+#include "util/ButtonNavigator.h"
+
+class EpubReaderBookmarkSelectionActivity final : public ActivityWithSubactivity {
+  std::shared_ptr<Epub> epub;
+  std::vector<Bookmark> bookmarks;
+  std::string cachePath;
+  TaskHandle_t displayTaskHandle = nullptr;
+  SemaphoreHandle_t renderingMutex = nullptr;
+  ButtonNavigator buttonNavigator;
+  int selectorIndex = 0;
+  bool updateRequired = false;
+  bool deleteConfirmMode = false;
+  bool ignoreNextConfirmRelease = false;
+  int pendingDeleteIndex = 0;
+  const std::function<void()> onGoBack;
+  const std::function<void(int newSpineIndex, int newPage)> onSelectBookmark;
+
+  // Number of items that fit on a page, derived from logical screen height.
+  int getPageItems() const;
+
+  int getTotalItems() const;
+
+  // Build the prefix portion of a bookmark label (chapter + snippet, without page suffix)
+  std::string getBookmarkPrefix(const Bookmark& bookmark) const;
+
+  // Build the page suffix (e.g. " - Page 5")
+  static std::string getPageSuffix(const Bookmark& bookmark);
+
+  static void taskTrampoline(void* param);
+  [[noreturn]] void displayTaskLoop();
+  void renderScreen();
+
+ public:
+  explicit EpubReaderBookmarkSelectionActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
+                                               const std::shared_ptr<Epub>& epub,
+                                               std::vector<Bookmark> bookmarks,
+                                               const std::string& cachePath,
+                                               const std::function<void()>& onGoBack,
+                                               const std::function<void(int newSpineIndex, int newPage)>& onSelectBookmark)
+      : ActivityWithSubactivity("EpubReaderBookmarkSelection", renderer, mappedInput),
+        epub(epub),
+        bookmarks(std::move(bookmarks)),
+        cachePath(cachePath),
+        onGoBack(onGoBack),
+        onSelectBookmark(onSelectBookmark) {}
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+};

src/activities/reader/EpubReaderMenuActivity.h

@@ -16,6 +16,7 @@ class EpubReaderMenuActivity final : public ActivityWithSubactivity {
   // Menu actions available from the reader menu.
   enum class MenuAction {
     ADD_BOOKMARK,
+    REMOVE_BOOKMARK,
     LOOKUP,
     LOOKED_UP_WORDS,
     ROTATE_SCREEN,
@@ -31,10 +32,11 @@ class EpubReaderMenuActivity final : public ActivityWithSubactivity {
   explicit EpubReaderMenuActivity(GfxRenderer& renderer, MappedInputManager& mappedInput, const std::string& title,
                                   const int currentPage, const int totalPages, const int bookProgressPercent,
                                   const uint8_t currentOrientation, const bool hasDictionary,
+                                  const bool isBookmarked,
                                   const std::function<void(uint8_t)>& onBack,
                                   const std::function<void(MenuAction)>& onAction)
       : ActivityWithSubactivity("EpubReaderMenu", renderer, mappedInput),
-        menuItems(buildMenuItems(hasDictionary)),
+        menuItems(buildMenuItems(hasDictionary, isBookmarked)),
         title(title),
         pendingOrientation(currentOrientation),
         currentPage(currentPage),
@@ -70,9 +72,13 @@ class EpubReaderMenuActivity final : public ActivityWithSubactivity {
   const std::function<void(uint8_t)> onBack;
   const std::function<void(MenuAction)> onAction;
 
-  static std::vector<MenuItem> buildMenuItems(bool hasDictionary) {
+  static std::vector<MenuItem> buildMenuItems(bool hasDictionary, bool isBookmarked) {
     std::vector<MenuItem> items;
-    items.push_back({MenuAction::ADD_BOOKMARK, "Add Bookmark"});
+    if (isBookmarked) {
+      items.push_back({MenuAction::REMOVE_BOOKMARK, "Remove Bookmark"});
+    } else {
+      items.push_back({MenuAction::ADD_BOOKMARK, "Add Bookmark"});
+    }
     if (hasDictionary) {
       items.push_back({MenuAction::LOOKUP, "Lookup Word"});
       items.push_back({MenuAction::LOOKED_UP_WORDS, "Lookup Word History"});

src/util/BookmarkStore.cpp

@@ -0,0 +1,158 @@
+#include "BookmarkStore.h"
+
+#include <HalStorage.h>
+
+#include <algorithm>
+
+std::string BookmarkStore::filePath(const std::string& cachePath) { return cachePath + "/bookmarks.bin"; }
+
+std::vector<Bookmark> BookmarkStore::load(const std::string& cachePath) {
+  std::vector<Bookmark> bookmarks;
+  FsFile f;
+  if (!Storage.openFileForRead("BKM", filePath(cachePath), f)) {
+    return bookmarks;
+  }
+
+  // File format v2: [version(1)] [count(2)] [entries...]
+  // Each entry: [spine(2)] [page(2)] [snippetLen(1)] [snippet(snippetLen)]
+  // v1 (no version byte): [count(2)] [entries of 4 bytes each]
+  // We detect v1 by checking if the first byte could be a version marker (0xFF).
+
+  uint8_t firstByte;
+  if (f.read(&firstByte, 1) != 1) {
+    f.close();
+    return bookmarks;
+  }
+
+  uint16_t count;
+  bool hasSnippets;
+
+  if (firstByte == 0xFF) {
+    // v2 format: version marker was 0xFF
+    hasSnippets = true;
+    uint8_t countBytes[2];
+    if (f.read(countBytes, 2) != 2) {
+      f.close();
+      return bookmarks;
+    }
+    count = static_cast<uint16_t>(countBytes[0]) | (static_cast<uint16_t>(countBytes[1]) << 8);
+  } else {
+    // v1 format: first byte was part of the count
+    hasSnippets = false;
+    uint8_t secondByte;
+    if (f.read(&secondByte, 1) != 1) {
+      f.close();
+      return bookmarks;
+    }
+    count = static_cast<uint16_t>(firstByte) | (static_cast<uint16_t>(secondByte) << 8);
+  }
+
+  if (count > MAX_BOOKMARKS) {
+    count = MAX_BOOKMARKS;
+  }
+
+  for (uint16_t i = 0; i < count; i++) {
+    uint8_t entry[4];
+    if (f.read(entry, 4) != 4) break;
+    Bookmark b;
+    b.spineIndex = static_cast<int16_t>(static_cast<uint16_t>(entry[0]) | (static_cast<uint16_t>(entry[1]) << 8));
+    b.pageNumber = static_cast<int16_t>(static_cast<uint16_t>(entry[2]) | (static_cast<uint16_t>(entry[3]) << 8));
+
+    if (hasSnippets) {
+      uint8_t snippetLen;
+      if (f.read(&snippetLen, 1) != 1) break;
+      if (snippetLen > 0) {
+        std::vector<uint8_t> buf(snippetLen);
+        if (f.read(buf.data(), snippetLen) != snippetLen) break;
+        b.snippet = std::string(buf.begin(), buf.end());
+      }
+    }
+
+    bookmarks.push_back(b);
+  }
+
+  f.close();
+  return bookmarks;
+}
+
+bool BookmarkStore::save(const std::string& cachePath, const std::vector<Bookmark>& bookmarks) {
+  FsFile f;
+  if (!Storage.openFileForWrite("BKM", filePath(cachePath), f)) {
+    Serial.printf("[%lu] [BKM] Could not save bookmarks!\n", millis());
+    return false;
+  }
+
+  // Write v2 format: version marker + count + entries with snippets
+  uint8_t version = 0xFF;
+  f.write(&version, 1);
+
+  uint16_t count = static_cast<uint16_t>(bookmarks.size());
+  uint8_t header[2] = {static_cast<uint8_t>(count & 0xFF), static_cast<uint8_t>((count >> 8) & 0xFF)};
+  f.write(header, 2);
+
+  for (const auto& b : bookmarks) {
+    uint8_t entry[4];
+    entry[0] = static_cast<uint8_t>(b.spineIndex & 0xFF);
+    entry[1] = static_cast<uint8_t>((b.spineIndex >> 8) & 0xFF);
+    entry[2] = static_cast<uint8_t>(b.pageNumber & 0xFF);
+    entry[3] = static_cast<uint8_t>((b.pageNumber >> 8) & 0xFF);
+    f.write(entry, 4);
+
+    // Write snippet: length byte + string data
+    uint8_t snippetLen = static_cast<uint8_t>(std::min(static_cast<int>(b.snippet.size()), MAX_SNIPPET_LENGTH));
+    f.write(&snippetLen, 1);
+    if (snippetLen > 0) {
+      f.write(reinterpret_cast<const uint8_t*>(b.snippet.c_str()), snippetLen);
+    }
+  }
+
+  f.close();
+  Serial.printf("[%lu] [BKM] Saved %d bookmarks\n", millis(), count);
+  return true;
+}
+
+bool BookmarkStore::addBookmark(const std::string& cachePath, int spineIndex, int page, const std::string& snippet) {
+  auto bookmarks = load(cachePath);
+
+  // Check for duplicate
+  for (const auto& b : bookmarks) {
+    if (b.spineIndex == spineIndex && b.pageNumber == page) {
+      return true;  // Already bookmarked
+    }
+  }
+
+  if (static_cast<int>(bookmarks.size()) >= MAX_BOOKMARKS) {
+    return false;
+  }
+
+  Bookmark b;
+  b.spineIndex = static_cast<int16_t>(spineIndex);
+  b.pageNumber = static_cast<int16_t>(page);
+  b.snippet = snippet.substr(0, MAX_SNIPPET_LENGTH);
+  bookmarks.push_back(b);
+
+  return save(cachePath, bookmarks);
+}
+
+bool BookmarkStore::removeBookmark(const std::string& cachePath, int spineIndex, int page) {
+  auto bookmarks = load(cachePath);
+
+  auto it = std::remove_if(bookmarks.begin(), bookmarks.end(),
+                           [spineIndex, page](const Bookmark& b) {
+                             return b.spineIndex == spineIndex && b.pageNumber == page;
+                           });
+
+  if (it == bookmarks.end()) {
+    return false;  // Not found
+  }
+
+  bookmarks.erase(it, bookmarks.end());
+  return save(cachePath, bookmarks);
+}
+
+bool BookmarkStore::hasBookmark(const std::string& cachePath, int spineIndex, int page) {
+  auto bookmarks = load(cachePath);
+  return std::any_of(bookmarks.begin(), bookmarks.end(), [spineIndex, page](const Bookmark& b) {
+    return b.spineIndex == spineIndex && b.pageNumber == page;
+  });
+}

src/util/BookmarkStore.h

@@ -0,0 +1,24 @@
+#pragma once
+#include <cstdint>
+#include <string>
+#include <vector>
+
+struct Bookmark {
+  int16_t spineIndex;
+  int16_t pageNumber;
+  std::string snippet;  // First sentence or text excerpt from the page
+};
+
+class BookmarkStore {
+ public:
+  static std::vector<Bookmark> load(const std::string& cachePath);
+  static bool save(const std::string& cachePath, const std::vector<Bookmark>& bookmarks);
+  static bool addBookmark(const std::string& cachePath, int spineIndex, int page, const std::string& snippet = "");
+  static bool removeBookmark(const std::string& cachePath, int spineIndex, int page);
+  static bool hasBookmark(const std::string& cachePath, int spineIndex, int page);
+
+ private:
+  static std::string filePath(const std::string& cachePath);
+  static constexpr int MAX_BOOKMARKS = 200;
+  static constexpr int MAX_SNIPPET_LENGTH = 120;
+};