From 3de07b925c8af5c58297524daa9b5230deff7142 Mon Sep 17 00:00:00 2001
From: Jonas Diemer <jonasdiemer@gmail.com>
Date: Sun, 4 Jan 2026 14:15:33 +0100
Subject: [PATCH] Refactor readRow to readNextRow (we anyways ignored rowY
 param)

---
 lib/GfxRenderer/Bitmap.cpp      | 18 ++++++------------
 lib/GfxRenderer/Bitmap.h        |  4 ++--
 lib/GfxRenderer/GfxRenderer.cpp |  2 +-
 3 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/lib/GfxRenderer/Bitmap.cpp b/lib/GfxRenderer/Bitmap.cpp
index 4dbe8a25..8cc8a5f3 100644
--- a/lib/GfxRenderer/Bitmap.cpp
+++ b/lib/GfxRenderer/Bitmap.cpp
@@ -250,35 +250,29 @@ BmpReaderError Bitmap::parseHeaders() {
     delete[] errorNextRow;
     errorCurRow = new int16_t[width + 2]();  // +2 for boundary handling
     errorNextRow = new int16_t[width + 2]();
-    lastRowY = -1;
+    prevRowY = -1;
   }
 
   return BmpReaderError::Ok;
 }
 
 // packed 2bpp output, 0 = black, 1 = dark gray, 2 = light gray, 3 = white
-// TODO: This seems to only work sequentially, rowY is mostly ignored
-BmpReaderError Bitmap::readRow(uint8_t* data, uint8_t* rowBuffer, int rowY) const {
+BmpReaderError Bitmap::readNextRow(uint8_t* data, uint8_t* rowBuffer) const {
   // Note: rowBuffer should be pre-allocated by the caller to size 'rowBytes'
   if (file.read(rowBuffer, rowBytes) != rowBytes) return BmpReaderError::ShortReadRow;
 
   // Handle Floyd-Steinberg error buffer progression
   const bool useFS = USE_FLOYD_STEINBERG && errorCurRow && errorNextRow;
   if (useFS) {
-    // Check if we need to advance to next row (or reset if jumping)
-    if (rowY != lastRowY + 1 && rowY != 0) {
-      // Non-sequential row access - reset error buffers
-      memset(errorCurRow, 0, (width + 2) * sizeof(int16_t));
-      memset(errorNextRow, 0, (width + 2) * sizeof(int16_t));
-    } else if (rowY > 0) {
+    if (prevRowY != -1) {
       // Sequential access - swap buffers
       int16_t* temp = errorCurRow;
       errorCurRow = errorNextRow;
       errorNextRow = temp;
       memset(errorNextRow, 0, (width + 2) * sizeof(int16_t));
     }
-    lastRowY = rowY;
   }
+  prevRowY += 1;
 
   uint8_t* outPtr = data;
   uint8_t currentOutByte = 0;
@@ -293,7 +287,7 @@ BmpReaderError Bitmap::readRow(uint8_t* data, uint8_t* rowBuffer, int rowY) cons
       color = quantizeFloydSteinberg(lum, currentX, width, errorCurRow, errorNextRow, false);
     } else {
       // Simple quantization or noise dithering
-      color = quantize(lum, currentX, rowY);
+      color = quantize(lum, currentX, prevRowY);
     }
     currentOutByte |= (color << bitShift);
     if (bitShift == 0) {
@@ -366,7 +360,7 @@ BmpReaderError Bitmap::rewindToData() const {
   if (USE_FLOYD_STEINBERG && errorCurRow && errorNextRow) {
     memset(errorCurRow, 0, (width + 2) * sizeof(int16_t));
     memset(errorNextRow, 0, (width + 2) * sizeof(int16_t));
-    lastRowY = -1;
+    prevRowY = -1;
   }
 
   return BmpReaderError::Ok;
diff --git a/lib/GfxRenderer/Bitmap.h b/lib/GfxRenderer/Bitmap.h
index 7e799647..a3f2e00c 100644
--- a/lib/GfxRenderer/Bitmap.h
+++ b/lib/GfxRenderer/Bitmap.h
@@ -31,7 +31,7 @@ class Bitmap {
   explicit Bitmap(FsFile& file) : file(file) {}
   ~Bitmap();
   BmpReaderError parseHeaders();
-  BmpReaderError readRow(uint8_t* data, uint8_t* rowBuffer, int rowY) const;
+  BmpReaderError readNextRow(uint8_t* data, uint8_t* rowBuffer) const;
   BmpReaderError rewindToData() const;
   int getWidth() const { return width; }
   int getHeight() const { return height; }
@@ -55,5 +55,5 @@ class Bitmap {
   // Floyd-Steinberg dithering state (mutable for const methods)
   mutable int16_t* errorCurRow = nullptr;
   mutable int16_t* errorNextRow = nullptr;
-  mutable int lastRowY = -1;  // Track row progression for error propagation
+  mutable int prevRowY = -1;  // Track row progression for error propagation
 };
diff --git a/lib/GfxRenderer/GfxRenderer.cpp b/lib/GfxRenderer/GfxRenderer.cpp
index 1750b3f3..cc1288a7 100644
--- a/lib/GfxRenderer/GfxRenderer.cpp
+++ b/lib/GfxRenderer/GfxRenderer.cpp
@@ -196,7 +196,7 @@ void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, con
       break;
     }
 
-    if (bitmap.readRow(outputRow, rowBytes, bmpY) != BmpReaderError::Ok) {
+    if (bitmap.readNextRow(outputRow, rowBytes) != BmpReaderError::Ok) {
       Serial.printf("[%lu] [GFX] Failed to read row %d from bitmap\n", millis(), bmpY);
       free(outputRow);
       free(rowBytes);