From 449b3ca161f501cd7c4029039683609e624abcce Mon Sep 17 00:00:00 2001
From: Dave Allie <dave@daveallie.com>
Date: Tue, 16 Dec 2025 02:16:35 +1100
Subject: [PATCH] Fixed light gray text rendering

---
 lib/GfxRenderer/GfxRenderer.cpp  | 16 +++++++++++-----
 lib/GfxRenderer/GfxRenderer.h    | 16 +++++++++-------
 src/screens/EpubReaderScreen.cpp |  6 +++---
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/lib/GfxRenderer/GfxRenderer.cpp b/lib/GfxRenderer/GfxRenderer.cpp
index dd33264..8199bd6 100644
--- a/lib/GfxRenderer/GfxRenderer.cpp
+++ b/lib/GfxRenderer/GfxRenderer.cpp
@@ -207,14 +207,20 @@ void GfxRenderer::renderChar(const EpdFontFamily& fontFamily, const uint32_t cp,
         if (is2Bit) {
           const uint8_t byte = bitmap[pixelPosition / 4];
           const uint8_t bit_index = (3 - pixelPosition % 4) * 2;
+          // the direct bit from the font is 0 -> white, 1 -> light gray, 2 -> dark gray, 3 -> black
+          // we swap this to better match the way images and screen think about colors:
+          // 0 -> black, 1 -> dark grey, 2 -> light grey, 3 -> white
+          const uint8_t bmpVal = 3 - (byte >> bit_index) & 0x3;
 
-          const uint8_t val = (byte >> bit_index) & 0x3;
-          if (fontRenderMode == BW && val > 0) {
+          if (renderMode == BW && bmpVal < 3) {
+            // Black (also paints over the grays in BW mode)
             drawPixel(screenX, screenY, pixelState);
-          } else if (fontRenderMode == GRAYSCALE_MSB && val == 1) {
-            // TODO: Not sure how this anti-aliasing goes on black backgrounds
+          } else if (renderMode == GRAYSCALE_MSB && (bmpVal == 1 || bmpVal == 2)) {
+            // Light gray (also mark the MSB if it's going to be a dark gray too)
+            // We have to flag pixels in reverse for the gray buffers, as 0 leave alone, 1 update
             drawPixel(screenX, screenY, false);
-          } else if (fontRenderMode == GRAYSCALE_LSB && val == 2) {
+          } else if (renderMode == GRAYSCALE_LSB && bmpVal == 1) {
+            // Dark gray
             drawPixel(screenX, screenY, false);
           }
         } else {
diff --git a/lib/GfxRenderer/GfxRenderer.h b/lib/GfxRenderer/GfxRenderer.h
index d7b5925..720bf70 100644
--- a/lib/GfxRenderer/GfxRenderer.h
+++ b/lib/GfxRenderer/GfxRenderer.h
@@ -7,17 +7,17 @@
 
 class GfxRenderer {
  public:
-  enum FontRenderMode { BW, GRAYSCALE_LSB, GRAYSCALE_MSB };
+  enum RenderMode { BW, GRAYSCALE_LSB, GRAYSCALE_MSB };
 
  private:
   EInkDisplay& einkDisplay;
-  FontRenderMode fontRenderMode;
+  RenderMode renderMode;
   std::map<int, EpdFontFamily> fontMap;
   void renderChar(const EpdFontFamily& fontFamily, uint32_t cp, int* x, const int* y, bool pixelState,
                   EpdFontStyle style) const;
 
  public:
-  explicit GfxRenderer(EInkDisplay& einkDisplay) : einkDisplay(einkDisplay), fontRenderMode(BW) {}
+  explicit GfxRenderer(EInkDisplay& einkDisplay) : einkDisplay(einkDisplay), renderMode(BW) {}
   ~GfxRenderer() = default;
 
   // Setup
@@ -41,15 +41,17 @@ class GfxRenderer {
   int getTextWidth(int fontId, const char* text, EpdFontStyle style = REGULAR) const;
   void drawCenteredText(int fontId, int y, const char* text, bool black = true, EpdFontStyle style = REGULAR) const;
   void drawText(int fontId, int x, int y, const char* text, bool black = true, EpdFontStyle style = REGULAR) const;
-  void setFontRenderMode(const FontRenderMode mode) { this->fontRenderMode = mode; }
   int getSpaceWidth(int fontId) const;
   int getLineHeight(int fontId) const;
 
+  // Grayscale functions
+  void setRenderMode(const RenderMode mode) { this->renderMode = mode; }
+  void copyGrayscaleLsbBuffers() const;
+  void copyGrayscaleMsbBuffers() const;
+  void displayGrayBuffer() const;
+
   // Low level functions
   uint8_t* getFrameBuffer() const;
   void swapBuffers() const;
   void grayscaleRevert() const;
-  void copyGrayscaleLsbBuffers() const;
-  void copyGrayscaleMsbBuffers() const;
-  void displayGrayBuffer() const;
 };
diff --git a/src/screens/EpubReaderScreen.cpp b/src/screens/EpubReaderScreen.cpp
index 4a42298..f2c51d9 100644
--- a/src/screens/EpubReaderScreen.cpp
+++ b/src/screens/EpubReaderScreen.cpp
@@ -301,19 +301,19 @@ void EpubReaderScreen::renderContents(std::unique_ptr<Page> page) {
   // TODO: Only do this if font supports it
   {
     renderer.clearScreen(0x00);
-    renderer.setFontRenderMode(GfxRenderer::GRAYSCALE_LSB);
+    renderer.setRenderMode(GfxRenderer::GRAYSCALE_LSB);
     page->render(renderer, READER_FONT_ID);
     renderer.copyGrayscaleLsbBuffers();
 
     // Render and copy to MSB buffer
     renderer.clearScreen(0x00);
-    renderer.setFontRenderMode(GfxRenderer::GRAYSCALE_MSB);
+    renderer.setRenderMode(GfxRenderer::GRAYSCALE_MSB);
     page->render(renderer, READER_FONT_ID);
     renderer.copyGrayscaleMsbBuffers();
 
     // display grayscale part
     renderer.displayGrayBuffer();
-    renderer.setFontRenderMode(GfxRenderer::BW);
+    renderer.setRenderMode(GfxRenderer::BW);
   }
 }