perf(ui): skip progress bar for chapters under 50KB

Always show "Indexing..." text, only add progress bar for >= 50KB chapters.

lib/Epub/Epub/ParsedText.cpp

@@ -106,6 +106,18 @@ std::vector<size_t> ParsedText::computeLineBreaks(const int pageWidth, const int
         ans[i] = j;  // j is the index of the last word in this optimal line
       }
     }
+
+    // Handle oversized word: if no valid configuration found, force single-word line
+    // This prevents cascade failure where one oversized word breaks all preceding words
+    if (dp[i] == MAX_COST) {
+      ans[i] = i;  // Just this word on its own line
+      // Inherit cost from next word to allow subsequent words to find valid configurations
+      if (i + 1 < static_cast<int>(totalWordCount)) {
+        dp[i] = dp[i + 1];
+      } else {
+        dp[i] = 0;
+      }
+    }
   }
 
   // Stores the index of the word that starts the next line (last_word_index + 1)

lib/Epub/Epub/Section.cpp

@@ -115,24 +115,39 @@ bool Section::clearCache() const {
 
 bool Section::persistPageDataToSD(const int fontId, const float lineCompression, const int marginTop,
                                   const int marginRight, const int marginBottom, const int marginLeft,
-                                  const bool extraParagraphSpacing, const std::function<void(int)>& progressFn) {
+                                  const bool extraParagraphSpacing, const std::function<void()>& progressSetupFn,
+                                  const std::function<void(int)>& progressFn) {
+  constexpr size_t MIN_SIZE_FOR_PROGRESS = 50 * 1024;  // 50KB
   const auto localPath = epub->getSpineItem(spineIndex).href;
   const auto tmpHtmlPath = epub->getCachePath() + "/.tmp_" + std::to_string(spineIndex) + ".html";
 
   // Retry logic for SD card timing issues
   bool success = false;
+  size_t fileSize = 0;
   for (int attempt = 0; attempt < 3 && !success; attempt++) {
     if (attempt > 0) {
       Serial.printf("[%lu] [SCT] Retrying stream (attempt %d)...\n", millis(), attempt + 1);
       delay(50);  // Brief delay before retry
     }
 
+    // Remove any incomplete file from previous attempt before retrying
+    if (SD.exists(tmpHtmlPath.c_str())) {
+      SD.remove(tmpHtmlPath.c_str());
+    }
+
     File tmpHtml;
     if (!FsHelpers::openFileForWrite("SCT", tmpHtmlPath, tmpHtml)) {
       continue;
     }
     success = epub->readItemContentsToStream(localPath, tmpHtml, 1024);
+    fileSize = tmpHtml.size();
     tmpHtml.close();
+
+    // If streaming failed, remove the incomplete file immediately
+    if (!success && SD.exists(tmpHtmlPath.c_str())) {
+      SD.remove(tmpHtmlPath.c_str());
+      Serial.printf("[%lu] [SCT] Removed incomplete temp file after failed attempt\n", millis());
+    }
   }
 
   if (!success) {
@@ -140,7 +155,12 @@ bool Section::persistPageDataToSD(const int fontId, const float lineCompression,
     return false;
   }
 
-  Serial.printf("[%lu] [SCT] Streamed temp HTML to %s\n", millis(), tmpHtmlPath.c_str());
+  Serial.printf("[%lu] [SCT] Streamed temp HTML to %s (%d bytes)\n", millis(), tmpHtmlPath.c_str(), fileSize);
+
+  // Only show progress bar for larger chapters where rendering overhead is worth it
+  if (progressSetupFn && fileSize >= MIN_SIZE_FOR_PROGRESS) {
+    progressSetupFn();
+  }
 
   ChapterHtmlSlimParser visitor(
       tmpHtmlPath, renderer, fontId, lineCompression, marginTop, marginRight, marginBottom, marginLeft,

lib/Epub/Epub/Section.h

@@ -33,6 +33,7 @@ class Section {
   bool clearCache() const;
   bool persistPageDataToSD(int fontId, float lineCompression, int marginTop, int marginRight, int marginBottom,
                            int marginLeft, bool extraParagraphSpacing,
+                           const std::function<void()>& progressSetupFn = nullptr,
                            const std::function<void(int)>& progressFn = nullptr);
   std::unique_ptr<Page> loadPageFromSD() const;
 };

lib/Epub/Epub/blocks/TextBlock.cpp

@@ -4,11 +4,18 @@
 #include <Serialization.h>
 
 void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int x, const int y) const {
+  // Validate iterator bounds before rendering
+  if (words.size() != wordXpos.size() || words.size() != wordStyles.size()) {
+    Serial.printf("[%lu] [TXB] Render skipped: size mismatch (words=%u, xpos=%u, styles=%u)\n", millis(),
+                  (uint32_t)words.size(), (uint32_t)wordXpos.size(), (uint32_t)wordStyles.size());
+    return;
+  }
+
   auto wordIt = words.begin();
   auto wordStylesIt = wordStyles.begin();
   auto wordXposIt = wordXpos.begin();
 
-  for (int i = 0; i < words.size(); i++) {
+  for (size_t i = 0; i < words.size(); i++) {
     renderer.drawText(fontId, *wordXposIt + x, y, wordIt->c_str(), true, *wordStylesIt);
 
     std::advance(wordIt, 1);
@@ -46,6 +53,13 @@ std::unique_ptr<TextBlock> TextBlock::deserialize(File& file) {
 
   // words
   serialization::readPod(file, wc);
+
+  // Sanity check: prevent allocation of unreasonably large lists (max 10000 words per block)
+  if (wc > 10000) {
+    Serial.printf("[%lu] [TXB] Deserialization failed: word count %u exceeds maximum\n", millis(), wc);
+    return nullptr;
+  }
+
   words.resize(wc);
   for (auto& w : words) serialization::readString(file, w);
 
@@ -59,6 +73,13 @@ std::unique_ptr<TextBlock> TextBlock::deserialize(File& file) {
   wordStyles.resize(sc);
   for (auto& s : wordStyles) serialization::readPod(file, s);
 
+  // Validate data consistency: all three lists must have the same size
+  if (wc != xc || wc != sc) {
+    Serial.printf("[%lu] [TXB] Deserialization failed: size mismatch (words=%u, xpos=%u, styles=%u)\n", millis(), wc,
+                  xc, sc);
+    return nullptr;
+  }
+
   // style
   serialization::readPod(file, style);
 

src/activities/reader/EpubReaderActivity.cpp

@@ -224,26 +224,37 @@ void EpubReaderActivity::renderScreen() {
       constexpr int barHeight = 10;
       constexpr int boxMargin = 20;
       const int textWidth = renderer.getTextWidth(READER_FONT_ID, "Indexing...");
-      const int boxWidth = (barWidth > textWidth ? barWidth : textWidth) + boxMargin * 2;
+      const int boxWidthWithBar = (barWidth > textWidth ? barWidth : textWidth) + boxMargin * 2;
-      const int boxHeight = renderer.getLineHeight(READER_FONT_ID) + barHeight + boxMargin * 3;
+      const int boxWidthNoBar = textWidth + boxMargin * 2;
-      const int boxX = (GfxRenderer::getScreenWidth() - boxWidth) / 2;
+      const int boxHeightWithBar = renderer.getLineHeight(READER_FONT_ID) + barHeight + boxMargin * 3;
+      const int boxHeightNoBar = renderer.getLineHeight(READER_FONT_ID) + boxMargin * 2;
+      const int boxXWithBar = (GfxRenderer::getScreenWidth() - boxWidthWithBar) / 2;
+      const int boxXNoBar = (GfxRenderer::getScreenWidth() - boxWidthNoBar) / 2;
       constexpr int boxY = 50;
-      const int barX = boxX + (boxWidth - barWidth) / 2;
+      const int barX = boxXWithBar + (boxWidthWithBar - barWidth) / 2;
       const int barY = boxY + renderer.getLineHeight(READER_FONT_ID) + boxMargin * 2;
 
-      // Draw initial indexing box with 0% progress
+      // Always show "Indexing..." text first
       {
-        renderer.fillRect(boxX, boxY, boxWidth, boxHeight, false);
+        renderer.fillRect(boxXNoBar, boxY, boxWidthNoBar, boxHeightNoBar, false);
-        renderer.drawText(READER_FONT_ID, boxX + boxMargin, boxY + boxMargin, "Indexing...");
+        renderer.drawText(READER_FONT_ID, boxXNoBar + boxMargin, boxY + boxMargin, "Indexing...");
-        renderer.drawRect(boxX + 5, boxY + 5, boxWidth - 10, boxHeight - 10);
+        renderer.drawRect(boxXNoBar + 5, boxY + 5, boxWidthNoBar - 10, boxHeightNoBar - 10);
-        // Draw empty progress bar outline
-        renderer.drawRect(barX, barY, barWidth, barHeight);
         renderer.displayBuffer();
         pagesUntilFullRefresh = 0;
       }
 
       section->setupCacheDir();
 
+      // Setup callback - only called for chapters >= 50KB, redraws with progress bar
+      auto progressSetup = [this, boxXWithBar, boxWidthWithBar, boxHeightWithBar, boxMargin, barX, barY, barWidth,
+                            barHeight]() {
+        renderer.fillRect(boxXWithBar, boxY, boxWidthWithBar, boxHeightWithBar, false);
+        renderer.drawText(READER_FONT_ID, boxXWithBar + boxMargin, boxY + boxMargin, "Indexing...");
+        renderer.drawRect(boxXWithBar + 5, boxY + 5, boxWidthWithBar - 10, boxHeightWithBar - 10);
+        renderer.drawRect(barX, barY, barWidth, barHeight);
+        renderer.displayBuffer();
+      };
+
       // Progress callback to update progress bar
       auto progressCallback = [this, barX, barY, barWidth, barHeight](int progress) {
         const int fillWidth = (barWidth - 2) * progress / 100;
@@ -252,7 +263,7 @@ void EpubReaderActivity::renderScreen() {
       };
 
       if (!section->persistPageDataToSD(READER_FONT_ID, lineCompression, marginTop, marginRight, marginBottom,
-                                        marginLeft, SETTINGS.extraParagraphSpacing, progressCallback)) {
+                                        marginLeft, SETTINGS.extraParagraphSpacing, progressSetup, progressCallback)) {
         Serial.printf("[%lu] [ERS] Failed to persist page data to SD\n", millis());
         section.reset();
         return;