From 9f31f80c80ff43390c5a3281679aeea9e441426d Mon Sep 17 00:00:00 2001
From: Dave Allie <dave@daveallie.com>
Date: Tue, 30 Dec 2025 17:52:42 +1000
Subject: [PATCH] Show previous title for unnamed spines (#158)

## Summary

* Show previous title for unnamed spines
* The spec is a little unclear, but there are plenty of cases where
chapters are split up in parts and should show the previous chapter's
title
* List TOC items instead of spine items in chapter select
* Bump `BOOK_CACHE_VERSION` to `2` to force regeneration of spine item's
TOC indexes
---
 lib/Epub/Epub/BookMetadataCache.cpp           | 10 ++++--
 .../EpubReaderChapterSelectionActivity.cpp    | 34 +++++++++++--------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/lib/Epub/Epub/BookMetadataCache.cpp b/lib/Epub/Epub/BookMetadataCache.cpp
index 6272414..6cc7ea7 100644
--- a/lib/Epub/Epub/BookMetadataCache.cpp
+++ b/lib/Epub/Epub/BookMetadataCache.cpp
@@ -9,7 +9,7 @@
 #include "FsHelpers.h"
 
 namespace {
-constexpr uint8_t BOOK_CACHE_VERSION = 1;
+constexpr uint8_t BOOK_CACHE_VERSION = 2;
 constexpr char bookBinFile[] = "/book.bin";
 constexpr char tmpSpineBinFile[] = "/spine.bin.tmp";
 constexpr char tmpTocBinFile[] = "/toc.bin.tmp";
@@ -143,6 +143,7 @@ bool BookMetadataCache::buildBookBin(const std::string& epubPath, const BookMeta
   }
   uint32_t cumSize = 0;
   spineFile.seek(0);
+  int lastSpineTocIndex = -1;
   for (int i = 0; i < spineCount; i++) {
     auto spineEntry = readSpineEntry(spineFile);
 
@@ -158,9 +159,12 @@ bool BookMetadataCache::buildBookBin(const std::string& epubPath, const BookMeta
     // Not a huge deal if we don't fine a TOC entry for the spine entry, this is expected behaviour for EPUBs
     // Logging here is for debugging
     if (spineEntry.tocIndex == -1) {
-      Serial.printf("[%lu] [BMC] Warning: Could not find TOC entry for spine item %d: %s\n", millis(), i,
-                    spineEntry.href.c_str());
+      Serial.printf(
+          "[%lu] [BMC] Warning: Could not find TOC entry for spine item %d: %s, using title from last section\n",
+          millis(), i, spineEntry.href.c_str());
+      spineEntry.tocIndex = lastSpineTocIndex;
     }
+    lastSpineTocIndex = spineEntry.tocIndex;
 
     // Calculate size for cumulative size
     size_t itemSize = 0;
diff --git a/src/activities/reader/EpubReaderChapterSelectionActivity.cpp b/src/activities/reader/EpubReaderChapterSelectionActivity.cpp
index 8245ed2..5f0cab2 100644
--- a/src/activities/reader/EpubReaderChapterSelectionActivity.cpp
+++ b/src/activities/reader/EpubReaderChapterSelectionActivity.cpp
@@ -39,7 +39,10 @@ void EpubReaderChapterSelectionActivity::onEnter() {
   }
 
   renderingMutex = xSemaphoreCreateMutex();
-  selectorIndex = currentSpineIndex;
+  selectorIndex = epub->getTocIndexForSpineIndex(currentSpineIndex);
+  if (selectorIndex == -1) {
+    selectorIndex = 0;
+  }
 
   // Trigger first update
   updateRequired = true;
@@ -74,22 +77,27 @@ void EpubReaderChapterSelectionActivity::loop() {
   const int pageItems = getPageItems();
 
   if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
-    onSelectSpineIndex(selectorIndex);
+    const auto newSpineIndex = epub->getSpineIndexForTocIndex(selectorIndex);
+    if (newSpineIndex == -1) {
+      onGoBack();
+    } else {
+      onSelectSpineIndex(newSpineIndex);
+    }
   } else if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
     onGoBack();
   } else if (prevReleased) {
     if (skipPage) {
       selectorIndex =
-          ((selectorIndex / pageItems - 1) * pageItems + epub->getSpineItemsCount()) % epub->getSpineItemsCount();
+          ((selectorIndex / pageItems - 1) * pageItems + epub->getTocItemsCount()) % epub->getTocItemsCount();
     } else {
-      selectorIndex = (selectorIndex + epub->getSpineItemsCount() - 1) % epub->getSpineItemsCount();
+      selectorIndex = (selectorIndex + epub->getTocItemsCount() - 1) % epub->getTocItemsCount();
     }
     updateRequired = true;
   } else if (nextReleased) {
     if (skipPage) {
-      selectorIndex = ((selectorIndex / pageItems + 1) * pageItems) % epub->getSpineItemsCount();
+      selectorIndex = ((selectorIndex / pageItems + 1) * pageItems) % epub->getTocItemsCount();
     } else {
-      selectorIndex = (selectorIndex + 1) % epub->getSpineItemsCount();
+      selectorIndex = (selectorIndex + 1) % epub->getTocItemsCount();
     }
     updateRequired = true;
   }
@@ -116,15 +124,11 @@ void EpubReaderChapterSelectionActivity::renderScreen() {
 
   const auto pageStartIndex = selectorIndex / pageItems * pageItems;
   renderer.fillRect(0, 60 + (selectorIndex % pageItems) * 30 - 2, pageWidth - 1, 30);
-  for (int i = pageStartIndex; i < epub->getSpineItemsCount() && i < pageStartIndex + pageItems; i++) {
-    const int tocIndex = epub->getTocIndexForSpineIndex(i);
-    if (tocIndex == -1) {
-      renderer.drawText(UI_FONT_ID, 20, 60 + (i % pageItems) * 30, "Unnamed", i != selectorIndex);
-    } else {
-      auto item = epub->getTocItem(tocIndex);
-      renderer.drawText(UI_FONT_ID, 20 + (item.level - 1) * 15, 60 + (i % pageItems) * 30, item.title.c_str(),
-                        i != selectorIndex);
-    }
+  for (int tocIndex = pageStartIndex; tocIndex < epub->getTocItemsCount() && tocIndex < pageStartIndex + pageItems;
+       tocIndex++) {
+    auto item = epub->getTocItem(tocIndex);
+    renderer.drawText(UI_FONT_ID, 20 + (item.level - 1) * 15, 60 + (tocIndex % pageItems) * 30, item.title.c_str(),
+                      tocIndex != selectorIndex);
   }
 
   renderer.displayBuffer();