fix: Port upstream 1.1.0-rc fixes (glyph null-safety, PNGdec wide image buffer)

Cherry-pick two bug fixes from upstream PR #992:

- fix(GfxRenderer): Null-safety in getSpaceWidth/getTextAdvanceX to
  prevent Load access fault when bold/italic font variants lack certain
  glyphs (upstream 3e2c518)
- fix(PNGdec): Increase PNG_MAX_BUFFERED_PIXELS to 16416 for 2048px
  wide images and add pre-decode buffer overflow guard (upstream b8e743e)

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

lib/Epub/Epub/converters/PngToFramebufferConverter.cpp

@@ -90,6 +90,32 @@ int32_t pngSeekWithHandle(PNGFILE* pFile, int32_t pos) {
 constexpr size_t PNG_DECODER_APPROX_SIZE = 44 * 1024;                          // ~42 KB + overhead
 constexpr size_t MIN_FREE_HEAP_FOR_PNG = PNG_DECODER_APPROX_SIZE + 16 * 1024;  // decoder + 16 KB headroom
 
+// PNGdec keeps TWO scanlines in its internal ucPixels buffer (current + previous)
+// and each scanline includes a leading filter byte.
+// Required storage is therefore approximately: 2 * (pitch + 1) + alignment slack.
+// If PNG_MAX_BUFFERED_PIXELS is smaller than this requirement for a given image,
+// PNGdec can overrun its internal buffer before our draw callback executes.
+int bytesPerPixelFromType(int pixelType) {
+  switch (pixelType) {
+    case PNG_PIXEL_TRUECOLOR:
+      return 3;
+    case PNG_PIXEL_GRAY_ALPHA:
+      return 2;
+    case PNG_PIXEL_TRUECOLOR_ALPHA:
+      return 4;
+    case PNG_PIXEL_GRAYSCALE:
+    case PNG_PIXEL_INDEXED:
+    default:
+      return 1;
+  }
+}
+
+int requiredPngInternalBufferBytes(int srcWidth, int pixelType) {
+  // +1 filter byte per scanline, *2 for current+previous lines, +32 for alignment margin.
+  int pitch = srcWidth * bytesPerPixelFromType(pixelType);
+  return ((pitch + 1) * 2) + 32;
+}
+
 // Convert entire source line to grayscale with alpha blending to white background.
 // For indexed PNGs with tRNS chunk, alpha values are stored at palette[768] onwards.
 // Processing the whole line at once improves cache locality and reduces per-pixel overhead.
@@ -304,6 +330,18 @@ bool PngToFramebufferConverter::decodeToFramebuffer(const std::string& imagePath
   LOG_DBG("PNG", "PNG %dx%d -> %dx%d (scale %.2f), bpp: %d", ctx.srcWidth, ctx.srcHeight, ctx.dstWidth, ctx.dstHeight,
           ctx.scale, png->getBpp());
 
+  const int pixelType = png->getPixelType();
+  const int requiredInternal = requiredPngInternalBufferBytes(ctx.srcWidth, pixelType);
+  if (requiredInternal > PNG_MAX_BUFFERED_PIXELS) {
+    LOG_ERR("PNG",
+            "PNG row buffer too small: need %d bytes for width=%d type=%d, configured PNG_MAX_BUFFERED_PIXELS=%d",
+            requiredInternal, ctx.srcWidth, pixelType, PNG_MAX_BUFFERED_PIXELS);
+    LOG_ERR("PNG", "Aborting decode to avoid PNGdec internal buffer overflow");
+    png->close();
+    delete png;
+    return false;
+  }
+
   if (png->getBpp() != 8) {
     warnUnsupportedFeature("bit depth (" + std::to_string(png->getBpp()) + "bpp)", imagePath);
   }

lib/GfxRenderer/GfxRenderer.cpp

@@ -824,7 +824,8 @@ int GfxRenderer::getSpaceWidth(const int fontId, const EpdFontFamily::Style styl
     return 0;
   }
 
-  return fontIt->second.getGlyph(' ', style)->advanceX;
+  const EpdGlyph* spaceGlyph = fontIt->second.getGlyph(' ', style);
+  return spaceGlyph ? spaceGlyph->advanceX : 0;
 }
 
 int GfxRenderer::getTextAdvanceX(const int fontId, const char* text, const EpdFontFamily::Style style) const {
@@ -838,7 +839,9 @@ int GfxRenderer::getTextAdvanceX(const int fontId, const char* text, const EpdFo
   int width = 0;
   const auto& font = fontIt->second;
   while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&text)))) {
-    width += font.getGlyph(cp, style)->advanceX;
+    const EpdGlyph* glyph = font.getGlyph(cp, style);
+    if (!glyph) glyph = font.getGlyph(REPLACEMENT_GLYPH, style);
+    if (glyph) width += glyph->advanceX;
   }
   return width;
 }

platformio.ini

@@ -2,7 +2,7 @@
 default_envs = default
 
 [crosspoint]
-version = 1.0.0
+version = 1.1.1-rc
 
 [base]
 platform = espressif32 @ 6.12.0
@@ -31,9 +31,9 @@ build_flags =
   -std=gnu++2a
 # Enable UTF-8 long file names in SdFat
   -DUSE_UTF8_LONG_NAMES=1
-# Increase PNG scanline buffer to support up to 800px wide images
+# Increase PNG scanline buffer to support up to 2048px wide images
 # Default is (320*4+1)*2=2562, we need more for larger images
-  -DPNG_MAX_BUFFERED_PIXELS=6402
+  -DPNG_MAX_BUFFERED_PIXELS=16416
 
 build_unflags =
   -std=gnu++11

src/activities/boot_sleep/SleepActivity.cpp

@@ -21,6 +21,11 @@
 #include "util/BookSettings.h"
 #include "util/StringUtils.h"
 
+// Sleep cover refresh strategy when dithered letterbox fill is active:
+// 1 = Double FAST_REFRESH (clear to white, then render content -- avoids HALF_REFRESH crosstalk)
+// 0 = Standard HALF_REFRESH (original behavior)
+#define USE_SLEEP_DOUBLE_FAST_REFRESH 1
+
 namespace {
 
 // Number of source pixels along the image edge to average for the dominant color
@@ -74,37 +79,6 @@ uint8_t quantizeBayerDither(int gray, int x, int y) {
   }
 }
 
-// Check whether a gray value would produce a dithered mix that crosses the
-// level-2 / level-3 boundary.  This is the ONLY boundary where some dithered
-// pixels are BLACK (level ≤ 2) and others are WHITE (level 3) in the BW pass,
-// creating a high-frequency checkerboard that causes e-ink display crosstalk
-// and washes out adjacent content during HALF_REFRESH.
-// Gray values 171-254 produce a level-2/level-3 mix via Bayer dithering.
-bool bayerCrossesBwBoundary(uint8_t gray) { return gray > 170 && gray < 255; }
-
-// Hash-based block dithering for BW-boundary gray values (171-254).
-// Each blockSize×blockSize pixel block gets a single uniform level (2 or 3),
-// determined by a deterministic spatial hash.  The proportion of level-3 blocks
-// approximates the target gray.  Unlike Bayer, the pattern is irregular
-// (noise-like), making it much less visually obvious at the same block size.
-// The hash is purely spatial (depends only on x, y, blockSize) so it produces
-// identical levels across BW, LSB, and MSB render passes.
-static constexpr int BW_DITHER_BLOCK = 2;
-
-uint8_t hashBlockDither(uint8_t avg, int x, int y) {
-  const int bx = x / BW_DITHER_BLOCK;
-  const int by = y / BW_DITHER_BLOCK;
-  // Fast mixing hash (splitmix32-inspired)
-  uint32_t h = (uint32_t)bx * 2654435761u ^ (uint32_t)by * 2246822519u;
-  h ^= h >> 16;
-  h *= 0x45d9f3bu;
-  h ^= h >> 16;
-  // Proportion of level-3 blocks needed to approximate the target gray
-  const float ratio = (avg - 170.0f) / 85.0f;
-  const uint32_t threshold = (uint32_t)(ratio * 4294967295.0f);
-  return (h < threshold) ? 3 : 2;
-}
-
 // --- Edge average cache ---
 // Caches the computed edge averages alongside the cover BMP so we don't rescan on every sleep.
 constexpr uint8_t EDGE_CACHE_VERSION = 2;
@@ -278,19 +252,6 @@ void drawLetterboxFill(GfxRenderer& renderer, const LetterboxFillData& data, uin
 
   const bool isSolid = (fillMode == CrossPointSettings::SLEEP_SCREEN_LETTERBOX_FILL::LETTERBOX_SOLID);
 
-  // For DITHERED mode with gray values in 171-254 (the level-2/level-3 BW boundary):
-  // Pixel-level Bayer dithering creates a regular high-frequency checkerboard in
-  // the BW pass that causes e-ink display crosstalk during HALF_REFRESH.
-  //
-  // Solution: HASH-BASED BLOCK DITHERING.  Each 2x2 pixel block gets a single
-  // level (2 or 3) determined by a spatial hash, with the proportion of level-3
-  // blocks tuned to approximate the target gray.  The 2px minimum run avoids BW
-  // crosstalk, and the irregular hash pattern is much less visible than a regular
-  // Bayer grid at the same block size.
-  const bool hashA = !isSolid && bayerCrossesBwBoundary(data.avgA);
-  const bool hashB = !isSolid && bayerCrossesBwBoundary(data.avgB);
-
-  // For solid mode: snap to nearest e-ink level
   const uint8_t levelA = isSolid ? snapToEinkLevel(data.avgA) / 85 : 0;
   const uint8_t levelB = isSolid ? snapToEinkLevel(data.avgB) / 85 : 0;
 
@@ -298,13 +259,7 @@ void drawLetterboxFill(GfxRenderer& renderer, const LetterboxFillData& data, uin
     if (data.letterboxA > 0) {
       for (int y = 0; y < data.letterboxA; y++)
         for (int x = 0; x < renderer.getScreenWidth(); x++) {
-          uint8_t lv;
+          const uint8_t lv = isSolid ? levelA : quantizeBayerDither(data.avgA, x, y);
-          if (isSolid)
-            lv = levelA;
-          else if (hashA)
-            lv = hashBlockDither(data.avgA, x, y);
-          else
-            lv = quantizeBayerDither(data.avgA, x, y);
           renderer.drawPixelGray(x, y, lv);
         }
     }
@@ -312,13 +267,7 @@ void drawLetterboxFill(GfxRenderer& renderer, const LetterboxFillData& data, uin
       const int start = renderer.getScreenHeight() - data.letterboxB;
       for (int y = start; y < renderer.getScreenHeight(); y++)
         for (int x = 0; x < renderer.getScreenWidth(); x++) {
-          uint8_t lv;
+          const uint8_t lv = isSolid ? levelB : quantizeBayerDither(data.avgB, x, y);
-          if (isSolid)
-            lv = levelB;
-          else if (hashB)
-            lv = hashBlockDither(data.avgB, x, y);
-          else
-            lv = quantizeBayerDither(data.avgB, x, y);
           renderer.drawPixelGray(x, y, lv);
         }
     }
@@ -326,13 +275,7 @@ void drawLetterboxFill(GfxRenderer& renderer, const LetterboxFillData& data, uin
     if (data.letterboxA > 0) {
       for (int x = 0; x < data.letterboxA; x++)
         for (int y = 0; y < renderer.getScreenHeight(); y++) {
-          uint8_t lv;
+          const uint8_t lv = isSolid ? levelA : quantizeBayerDither(data.avgA, x, y);
-          if (isSolid)
-            lv = levelA;
-          else if (hashA)
-            lv = hashBlockDither(data.avgA, x, y);
-          else
-            lv = quantizeBayerDither(data.avgA, x, y);
           renderer.drawPixelGray(x, y, lv);
         }
     }
@@ -340,13 +283,7 @@ void drawLetterboxFill(GfxRenderer& renderer, const LetterboxFillData& data, uin
       const int start = renderer.getScreenWidth() - data.letterboxB;
       for (int x = start; x < renderer.getScreenWidth(); x++)
         for (int y = 0; y < renderer.getScreenHeight(); y++) {
-          uint8_t lv;
+          const uint8_t lv = isSolid ? levelB : quantizeBayerDither(data.avgB, x, y);
-          if (isSolid)
-            lv = levelB;
-          else if (hashB)
-            lv = hashBlockDither(data.avgB, x, y);
-          else
-            lv = quantizeBayerDither(data.avgB, x, y);
           renderer.drawPixelGray(x, y, lv);
         }
     }
@@ -543,35 +480,47 @@ void SleepActivity::renderBitmapSleepScreen(const Bitmap& bitmap, const std::str
   const bool hasGreyscale = bitmap.hasGreyscale() &&
                             SETTINGS.sleepScreenCoverFilter == CrossPointSettings::SLEEP_SCREEN_COVER_FILTER::NO_FILTER;
 
-  // Draw letterbox fill (BW pass)
+  const bool isInverted =
-  if (fillData.valid) {
+      SETTINGS.sleepScreenCoverFilter == CrossPointSettings::SLEEP_SCREEN_COVER_FILTER::INVERTED_BLACK_AND_WHITE;
-    drawLetterboxFill(renderer, fillData, fillMode);
+
+#if USE_SLEEP_DOUBLE_FAST_REFRESH
+  const bool useDoubleFast =
+      fillData.valid && fillMode == CrossPointSettings::SLEEP_SCREEN_LETTERBOX_FILL::LETTERBOX_DITHERED;
+#else
+  const bool useDoubleFast = false;
+#endif
+
+  if (useDoubleFast) {
+    // Double FAST_REFRESH technique: avoids HALF_REFRESH crosstalk with dithered letterbox.
+    // Pass 1: clear to white baseline
+    renderer.clearScreen();
+    renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+
+    // Pass 2: render actual content and display
+    if (fillData.valid) drawLetterboxFill(renderer, fillData, fillMode);
+    renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, cropX, cropY);
+    if (isInverted) renderer.invertScreen();
+    renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+  } else {
+    // Standard path: single HALF_REFRESH
+    if (fillData.valid) drawLetterboxFill(renderer, fillData, fillMode);
+    renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, cropX, cropY);
+    if (isInverted) renderer.invertScreen();
+    renderer.displayBuffer(HalDisplay::HALF_REFRESH);
   }
 
-  renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, cropX, cropY);
-
-  if (SETTINGS.sleepScreenCoverFilter == CrossPointSettings::SLEEP_SCREEN_COVER_FILTER::INVERTED_BLACK_AND_WHITE) {
-    renderer.invertScreen();
-  }
-
-  renderer.displayBuffer(HalDisplay::HALF_REFRESH);
-
   if (hasGreyscale) {
     bitmap.rewindToData();
     renderer.clearScreen(0x00);
     renderer.setRenderMode(GfxRenderer::GRAYSCALE_LSB);
-    if (fillData.valid) {
+    if (fillData.valid) drawLetterboxFill(renderer, fillData, fillMode);
-      drawLetterboxFill(renderer, fillData, fillMode);
-    }
     renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, cropX, cropY);
     renderer.copyGrayscaleLsbBuffers();
 
     bitmap.rewindToData();
     renderer.clearScreen(0x00);
     renderer.setRenderMode(GfxRenderer::GRAYSCALE_MSB);
-    if (fillData.valid) {
+    if (fillData.valid) drawLetterboxFill(renderer, fillData, fillMode);
-      drawLetterboxFill(renderer, fillData, fillMode);
-    }
     renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, cropX, cropY);
     renderer.copyGrayscaleMsbBuffers();