Merge branch 'perf-uifonts2' of https://github.com/jpirnay/crosspoint-reader into mybuild

lib/GfxRenderer/GfxRenderer.cpp

@@ -63,6 +63,512 @@ static inline void rotateCoordinates(const GfxRenderer::Orientation orientation,
 
 enum class TextRotation { None, Rotated90CW };
 
+// =============================================================================
+// Fast-path glyph rendering helpers (1-bit BW fonts, TextRotation::None)
+// =============================================================================
+//
+// OVERVIEW
+// --------
+// The legacy path called drawPixel() once per set glyph pixel.  drawPixel()
+// invokes rotateCoordinates() (a switch), does a bounds check, logs on OOB,
+// then writes one bit.  For a typical 10×14 UI glyph that is ~100 calls.
+//
+// This fast path eliminates drawPixel() entirely by writing directly to the
+// framebuffer in up to 8-pixel chunks via writeRowBits().
+//
+// FRAMEBUFFER LAYOUT
+// ------------------
+// 1 bpp, MSB-first, DISPLAY_WIDTH (800) pixels per row stored in
+// DISPLAY_WIDTH_BYTES (100) bytes.  Bit 7 of byte 0 = leftmost pixel of
+// row 0.  "Physical row" phyY occupies bytes [phyY*100 .. phyY*100+99].
+// A set bit (1) is WHITE; a cleared bit (0) is BLACK.
+//
+// LANDSCAPE ORIENTATIONS  (2.5–3.1× speedup vs legacy)
+// -------------------------------------------------------
+// phyX and phyY are both linear functions of glyphX/glyphY in these modes,
+// so each glyph row maps directly to a physical framebuffer row.
+//
+//   LandscapeCounterClockwise:  phyX = screenXBase+glyphX,  phyY = screenYBase+glyphY
+//   LandscapeClockwise:         phyX = W-1-screenXBase-glyphX, phyY = H-1-screenYBase-glyphY
+//
+// Strategy: outer loop over glyphY (one physical row per iteration), inner
+// loop reads 8-pixel chunks of that glyph row with bitmapExtract() and writes
+// them with writeRowBits().  Bitmap access is purely sequential — fastest.
+// LandscapeClockwise iterates glyph chunks right-to-left and applies
+// reverseBits8() to flip horizontal direction.
+//
+// PORTRAIT ORIENTATIONS  (~2× speedup vs legacy)
+// -----------------------------------------------
+// Portrait (90° CW panel rotation):
+//   phyX = screenYBase+glyphY,  phyY = H-1-screenXBase-glyphX
+// PortraitInverted (90° CCW panel rotation):
+//   phyX = W-1-screenYBase-glyphY, phyY = screenXBase+glyphX
+//
+// Here glyph COLUMNS map to physical rows.  Naively iterating column-by-column
+// reads the bitmap with stride glyphWidth — cache-unfriendly and one bit at a
+// time.  Instead we use an 8×8 bit-matrix transpose:
+//
+//   For each 8-row × 8-column glyph block:
+//     1. Read 8 consecutive glyph rows (sequential bitmap access) into the
+//        top 8 bytes of a uint64_t (one bitmapExtract per row).
+//     2. Call transpose8x8() — an O(log 8) butterfly transform — to swap
+//        the role of rows and columns in 3 passes of XOR-masking.
+//     3. The resulting uint64_t holds 8 column bytes: byte k contains the
+//        bits for glyph column glyphX+k, one per physical row, MSB-aligned.
+//     4. Write each column byte with writeRowBits() to its physical row.
+//
+// For PortraitInverted the glyph rows are packed in reverse order (last row
+// at MSB of the uint64_t) before transposing.  This ensures the post-transpose
+// column bytes are already correctly ordered (MSB = leftmost phyX) without any
+// per-column bit-reversal step.
+//
+// PARAMETERS
+// ----------
+//   screenXBase = cursorX + glyph->left  (logical X of glyph pixel [0,0])
+//   screenYBase = cursorY - glyph->top   (logical Y of glyph pixel [0,0])
+
+// Reverse all 8 bits of a byte (bit 7 ↔ bit 0).
+static inline uint8_t reverseBits8(uint8_t b) {
+  b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
+  b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
+  b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
+  return b;
+}
+
+// Transpose an 8×8 bit matrix packed into a uint64_t.
+//
+// Input layout (row-major, row 0 at MSB):
+//   bit (63 - 8*r - c)  =  matrix[r][c]   (r=row 0..7, c=col 0..7)
+//
+// After transposition:
+//   bit (63 - 8*c - r)  =  matrix[r][c]
+//   i.e. byte k = bits [63-8k .. 56-8k] holds column k, MSB = row 0.
+//
+// Uses the classic 3-pass butterfly (Warren, "Hacker's Delight" §7-3):
+//   pass 1 swaps adjacent bit-pairs across a stride of 7 (nibble level),
+//   pass 2 swaps across stride 14 (byte level),
+//   pass 3 swaps across stride 28 (half-word level).
+static inline uint64_t transpose8x8(uint64_t x) {
+  uint64_t t;
+  t = (x ^ (x >> 7)) & 0x00AA00AA00AA00AAULL;
+  x ^= t ^ (t << 7);
+  t = (x ^ (x >> 14)) & 0x0000CCCC0000CCCCULL;
+  x ^= t ^ (t << 14);
+  t = (x ^ (x >> 28)) & 0x00000000F0F0F0F0ULL;
+  x ^= t ^ (t << 28);
+  return x;
+}
+
+// Extract up to 8 bits from a 1-bit MSB-first packed bitmap starting at bit
+// position 'bitPos'.  Returns them MSB-aligned (bit 7 = first extracted bit);
+// the lower (8-count) bits are zeroed.
+// All 'count' bits must lie within the valid bitmap byte range.
+static inline uint8_t bitmapExtract(const uint8_t* bitmap, const int bitPos, const int count) {
+  const int byteIdx = bitPos >> 3;
+  const int bitOff = bitPos & 7;
+  uint8_t result;
+  if (bitOff == 0) {
+    result = bitmap[byteIdx];
+  } else if (count <= 8 - bitOff) {
+    result = bitmap[byteIdx] << bitOff;  // all bits inside first byte
+  } else {
+    result = (uint8_t)(((uint16_t)bitmap[byteIdx] << 8 | bitmap[byteIdx + 1]) >> (8 - bitOff));
+  }
+  if (count < 8) result &= static_cast<uint8_t>(0xFF << (8 - count));
+  return result;
+}
+
+// ---------------------------------------------------------------------------
+// Fast glyph render pipeline
+// ---------------------------------------------------------------------------
+// Both 1-bit (BW) and 2-bit (antialiased) paths share the same structure:
+//
+//   gather → [reindex] → scatter
+//
+// The glyph bitmap is a row-major 2D tensor [glyphHeight][glyphWidth].
+// The framebuffer is a row-major 2D tensor [DISPLAY_HEIGHT][DISPLAY_WIDTH_BYTES]
+// (1 bpp) with a fixed row stride of DISPLAY_WIDTH_BYTES bytes.
+//
+// Non-rotated (Landscape): glyph rows map 1-to-1 to framebuffer rows.
+// Reindex is a no-op; the pipeline is a tight per-row gather+scatter loop.
+//
+// Rotated 90° (Portrait): glyph rows become framebuffer columns.
+// A row↔column axis swap (reindex) is required before scattering.
+//
+// 1-bit pipeline
+//   gather  : extractGlyphBlock        reads an 8×8 glyph tile into a
+//                                      contiguous uint64_t block
+//                                      (≈ glyphTensor[tile].contiguous())
+//   reindex : transpose8x8             swaps row↔column axes in the uint64_t;
+//                                      pure index transform, no data movement
+//   scatter : scatterBlockToFrameBuffer → writeRowBits
+//                                      writes each column-byte to its row
+//
+// 2-bit pipeline (why it differs)
+//   The glyph stores 4 gray levels (0–3). Rendering reduces these to a 1-bit
+//   draw/skip decision via a render-mode threshold. That reduction is
+//   information-lossy, so gather and threshold cannot be separated — there is
+//   no contiguous 2-bit block to transpose. The two steps are fused:
+//
+//   gather+threshold : build2BitRowMask  Landscape — samples along glyph X
+//                      build2BitColMask  Portrait  — samples along glyph Y
+//                      both return a 1-bit mask ready for writeRowBits
+//   scatter          : writeRowBits      same atom as the 1-bit path
+// ---------------------------------------------------------------------------
+
+// Scatter atom: merges 8 MSB-aligned bits into the framebuffer row at physical bit offset phyBitPos.
+// Shared by both pipelines (1-bit: via scatterBlockToFrameBuffer; 2-bit: called directly).
+//   bits      — MSB-aligned; bit 7 = pixel at phyBitPos, lower (8-count) bits are zero.
+//   phyBitPos — physical X of the MSB pixel; may be negative for left-edge partial chunks.
+//   pixelState true → black (clear bits to 0), false → white (set bits to 1).
+static inline void writeRowBits(uint8_t* const row, const int phyBitPos, const uint8_t bits, const bool pixelState) {
+  uint8_t effectiveBits = bits;
+  int byteIdx;
+  int shift;
+  if (phyBitPos < 0) {
+    // Chunk starts off-screen left: clip by shifting out the off-screen MSBs.
+    // bits is MSB-aligned, so (bits << neg) discards the neg off-screen pixels
+    // and leaves the on-screen pixels MSB-aligned starting at physical X=0.
+    const int neg = -phyBitPos;
+    if (neg >= 8) return;  // entire chunk is off-screen left
+    effectiveBits = bits << neg;
+    byteIdx = 0;
+    shift = 0;
+  } else {
+    byteIdx = phyBitPos >> 3;
+    shift = phyBitPos & 7;
+  }
+  if (pixelState) {
+    row[byteIdx] &= ~(effectiveBits >> shift);
+    if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES)
+      row[byteIdx + 1] &= ~(uint8_t)(effectiveBits << (8 - shift));
+  } else {
+    row[byteIdx] |= (effectiveBits >> shift);
+    if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES)
+      row[byteIdx + 1] |= (uint8_t)(effectiveBits << (8 - shift));
+  }
+}
+
+// 1-bit pipeline step 1 — gather: reads an up-to-8×8 tile from the glyph tensor
+// ([glyphHeight][glyphWidth], 1 bpp, row stride = glyphWidth bits) into a contiguous uint64_t.
+// Equivalent to glyphTensor[glyphY:+rowCount, glyphX:+colCount].contiguous().
+// Byte 7 = first source row (MSB-aligned). reverseRows implements a negative-stride gather along Y
+// (reads rows bottom-to-top), needed for PortraitInverted.
+// Full pipeline: extractGlyphBlock (gather) → transpose8x8 (reindex) → scatterBlockToFrameBuffer (scatter).
+static inline uint64_t extractGlyphBlock(const uint8_t* const bitmap, const int stride, const int glyphX,
+                                         const int glyphY, const int rowCount, const int colCount,
+                                         const bool reverseRows) {
+  uint64_t pack = 0;
+  int bitStart = glyphY * stride + glyphX;
+  for (int n = 0; n < rowCount; n++, bitStart += stride) {
+    const int slot = reverseRows ? (rowCount - 1 - n) : n;
+    pack |= static_cast<uint64_t>(bitmapExtract(bitmap, bitStart, colCount)) << (56 - 8 * slot);
+  }
+  return pack;
+}
+
+// 1-bit pipeline step 3 — scatter: writes column-bytes of the transposed block into framebuffer rows.
+// The framebuffer is a 2D tensor [DISPLAY_HEIGHT][DISPLAY_WIDTH_BYTES] with non-unit row stride;
+// phyYStride=±1 selects the traversal direction along Y (positive = top-to-bottom, negative = inverted).
+// Each column k maps to row (phyYBase + k*phyYStride) via writeRowBits.
+static inline void scatterBlockToFrameBuffer(uint8_t* const frameBuffer, const uint64_t pack, const int colCount,
+                                             const int phyYBase, const int phyYStride, const int phyBitPos,
+                                             const bool pixelState) {
+  for (int k = 0; k < colCount; k++) {
+    const uint8_t cols_k = static_cast<uint8_t>(pack >> (56 - 8 * k));
+    if (cols_k == 0) continue;
+    const int phyY = phyYBase + k * phyYStride;
+    if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+    writeRowBits(frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES, phyBitPos, cols_k, pixelState);
+  }
+}
+
+static void renderGlyphFastBW(uint8_t* const frameBuffer, const uint8_t* const bitmap, const int glyphWidth,
+                              const int glyphHeight, const int screenXBase, const int screenYBase,
+                              const bool pixelState, const GfxRenderer::Orientation orientation) {
+  switch (orientation) {
+    case GfxRenderer::LandscapeCounterClockwise: {
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY++) {
+        const int phyY = screenYBase + glyphY;
+        if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+        uint8_t* const row = frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES;
+        const int rowBitStart = glyphY * glyphWidth;
+        for (int glyphX = 0; glyphX < glyphWidth; glyphX += 8) {
+          const int count = std::min(8, glyphWidth - glyphX);
+          const uint8_t gbyte = bitmapExtract(bitmap, rowBitStart + glyphX, count);
+          if (gbyte == 0) continue;
+          const int phyBitPos = screenXBase + glyphX;
+          if (phyBitPos + count <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+          writeRowBits(row, phyBitPos, gbyte, pixelState);
+        }
+      }
+      break;
+    }
+
+    case GfxRenderer::LandscapeClockwise: {
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY++) {
+        const int phyY = HalDisplay::DISPLAY_HEIGHT - 1 - (screenYBase + glyphY);
+        if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+        uint8_t* const row = frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES;
+        const int rowBitStart = glyphY * glyphWidth;
+        for (int chunkEnd = glyphWidth - 1; chunkEnd >= 0; chunkEnd -= 8) {
+          const int chunkStart = std::max(0, chunkEnd - 7);
+          const int count = chunkEnd - chunkStart + 1;
+          const uint8_t gbyte_fwd = bitmapExtract(bitmap, rowBitStart + chunkStart, count);
+          const uint8_t gbyte = reverseBits8(gbyte_fwd >> (8 - count));
+          if (gbyte == 0) continue;
+          const int phyBitPos = HalDisplay::DISPLAY_WIDTH - 1 - screenXBase - chunkEnd;
+          if (phyBitPos + count <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+          writeRowBits(row, phyBitPos, gbyte, pixelState);
+        }
+      }
+      break;
+    }
+
+    case GfxRenderer::Portrait: {
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY += 8) {
+        const int rowCount = std::min(8, glyphHeight - glyphY);
+        const int phyBitPos = screenYBase + glyphY;
+        if (phyBitPos + rowCount <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+        for (int glyphX = 0; glyphX < glyphWidth; glyphX += 8) {
+          const int colCount = std::min(8, glyphWidth - glyphX);
+          const uint64_t pack =
+              transpose8x8(extractGlyphBlock(bitmap, glyphWidth, glyphX, glyphY, rowCount, colCount, false));
+          scatterBlockToFrameBuffer(frameBuffer, pack, colCount, HalDisplay::DISPLAY_HEIGHT - 1 - screenXBase - glyphX,
+                                    -1, phyBitPos, pixelState);
+        }
+      }
+      break;
+    }
+
+    case GfxRenderer::PortraitInverted: {
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY += 8) {
+        const int rowCount = std::min(8, glyphHeight - glyphY);
+        const int phyBitPos = HalDisplay::DISPLAY_WIDTH - 1 - screenYBase - (glyphY + rowCount - 1);
+        if (phyBitPos + rowCount <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+        for (int glyphX = 0; glyphX < glyphWidth; glyphX += 8) {
+          const int colCount = std::min(8, glyphWidth - glyphX);
+          const uint64_t pack =
+              transpose8x8(extractGlyphBlock(bitmap, glyphWidth, glyphX, glyphY, rowCount, colCount, true));
+          scatterBlockToFrameBuffer(frameBuffer, pack, colCount, screenXBase + glyphX, 1, phyBitPos, pixelState);
+        }
+      }
+      break;
+    }
+  }
+}
+
+// Read one pixel from a tightly-packed 2-bit-per-pixel glyph bitmap.
+// The bitmap is a row-major tensor [glyphHeight][glyphWidth] with no row padding;
+// its pixel-row stride equals glyphWidth.  pixelPosition = row * glyphWidth + col.
+// Returns the raw font value: 0=white, 1=light-gray, 2=dark-gray, 3=black.
+static inline uint8_t get2BitPixel(const uint8_t* const bitmap, const int pixelPosition) {
+  return (bitmap[pixelPosition >> 2] >> ((3 - (pixelPosition & 3)) * 2)) & 0x3;
+}
+
+// Convenience overload using explicit row/col/stride (tensor element access).
+static inline uint8_t get2BitPixel(const uint8_t* const bitmap, const int stride, const int row, const int col) {
+  return get2BitPixel(bitmap, row * stride + col);
+}
+
+template <GfxRenderer::RenderMode mode>
+static constexpr uint8_t drawMaskFor2BitMode() {
+  if constexpr (mode == GfxRenderer::BW)
+    return 0x0E;  // draw raw {1,2,3}
+  else if constexpr (mode == GfxRenderer::GRAYSCALE_MSB)
+    return 0x06;  // draw raw {1,2}
+  else
+    return 0x04;  // GRAYSCALE_LSB: draw raw {2}
+}
+
+// 2-bit pipeline — fused gather+threshold (X axis): the 2-bit analog of extractGlyphBlock, but
+// gather and threshold are collapsed into one pass. The threshold (2-bit raw value → 1-bit on/off)
+// is information-lossy, so no contiguous 2-bit intermediate block can be formed mid-pipeline.
+// The resulting 1-bit mask feeds writeRowBits directly (scatter). build2BitColMask is the Y-axis counterpart.
+template <GfxRenderer::RenderMode mode>
+static inline uint8_t build2BitRowMask(const uint8_t* const bitmap, const int rowStartPixel, const int glyphXStartOrEnd,
+                                       const int count, const bool reverseXInChunk) {
+  // drawMask uses raw 2-bit glyph values directly from font bitmaps:
+  // raw 0=white, 1=light gray, 2=dark gray, 3=black.
+  // Bit N set means: draw/update when raw==N.
+  // Compile-time constant lets the compiler reduce (drawMask >> raw) & 1 to a single comparison.
+  constexpr uint8_t drawMask = drawMaskFor2BitMode<mode>();
+
+  uint8_t mask = 0;
+  for (int i = 0; i < count; i++) {
+    const int logicalX = reverseXInChunk ? (glyphXStartOrEnd - i) : (glyphXStartOrEnd + i);
+    const uint8_t raw = get2BitPixel(bitmap, rowStartPixel + logicalX);
+    if ((drawMask >> raw) & 0x01) mask |= static_cast<uint8_t>(1u << (7 - i));
+  }
+  return mask;
+}
+
+// Fast-path 2-bit mask builder for 8 byte-aligned pixels.
+//
+// The 2-bit glyph bitmap stores 4 pixels per byte, MSB-first:
+//   byte b = [p0.msb p0.lsb  p1.msb p1.lsb  p2.msb p2.lsb  p3.msb p3.lsb]
+//
+// For each render mode the draw decision collapses to a two-bit boolean:
+//   BW            (draw if raw ≠ 0):      msb | lsb
+//   GRAYSCALE_MSB (draw if raw ∈ {1,2}):  msb ^ lsb
+//   GRAYSCALE_LSB (draw if raw == 2):     msb & ~lsb
+//
+// Derivation for one byte:
+//   msb_bits = b & 0xAA  →  bits 7,5,3,1 hold p0.msb … p3.msb; bits 6,4,2,0 = 0
+//   lsb_bits = (b & 0x55) << 1  →  same positions hold p0.lsb … p3.lsb
+//   draw_bits = msb_bits OP lsb_bits  →  bits 7,5,3,1 are the per-pixel draw flags
+//
+// compact4: squeezes those 4 draw flags from bit positions 7,5,3,1
+//   into the top nibble (bits 7,6,5,4 → pixels 0,1,2,3).
+//
+// Two bytes b0 (pixels 0–3) and b1 (pixels 4–7) are combined:
+//   mask = compact4(draw(b0)) | (compact4(draw(b1)) >> 4)
+//
+// This avoids the 8-iteration per-pixel loop in build2BitRowMask and
+// processes the full 8-pixel chunk in ~16 ALU ops instead of ~56.
+// The caller is responsible for only calling this when pixelStart is
+// 4-pixel (1-byte) aligned (pixelStart & 3 == 0) and count == 8.
+template <GfxRenderer::RenderMode mode>
+static inline uint8_t build2BitRowMaskFromTwoBytes(const uint8_t b0, const uint8_t b1) {
+  const uint8_t msb0 = b0 & 0xAA;
+  const uint8_t lsb0 = (b0 & 0x55) << 1;
+  const uint8_t msb1 = b1 & 0xAA;
+  const uint8_t lsb1 = (b1 & 0x55) << 1;
+
+  uint8_t draw0, draw1;
+  if constexpr (mode == GfxRenderer::BW) {
+    draw0 = msb0 | lsb0;
+    draw1 = msb1 | lsb1;
+  } else if constexpr (mode == GfxRenderer::GRAYSCALE_MSB) {
+    draw0 = msb0 ^ lsb0;
+    draw1 = msb1 ^ lsb1;
+  } else {  // GRAYSCALE_LSB
+    draw0 = msb0 & ~lsb0;
+    draw1 = msb1 & ~lsb1;
+  }
+
+  // Compact each nibble's draw flags from bit positions 7,5,3,1 → 7,6,5,4.
+  auto compact4 = [](const uint8_t d) -> uint8_t {
+    return (d & 0x80) | ((d & 0x20) << 1) | ((d & 0x08) << 2) | ((d & 0x02) << 3);
+  };
+  return compact4(draw0) | (compact4(draw1) >> 4);
+}
+
+// 2-bit pipeline — fused gather+threshold (Y axis): column-direction counterpart to build2BitRowMask.
+// Samples count pixels down glyph column glyphX starting at row glyphYStart; reverseRows implements
+// a negative-stride view along Y (reads bottom-to-top), needed for PortraitInverted.
+template <GfxRenderer::RenderMode mode>
+static inline uint8_t build2BitColMask(const uint8_t* const bitmap, const int glyphWidth, const int glyphX,
+                                       const int glyphYStart, const int count, const bool reverseRows) {
+  constexpr uint8_t drawMask = drawMaskFor2BitMode<mode>();
+  uint8_t mask = 0;
+  for (int i = 0; i < count; i++) {
+    const int row = reverseRows ? (glyphYStart + count - 1 - i) : (glyphYStart + i);
+    const uint8_t raw = get2BitPixel(bitmap, glyphWidth, row, glyphX);
+    if ((drawMask >> raw) & 0x01) mask |= static_cast<uint8_t>(1u << (7 - i));
+  }
+  return mask;
+}
+
+// Shared body for Portrait and PortraitInverted 2-bit rendering.
+// inverted=false → Portrait (phyY counts down, phyBitPos counts up).
+// inverted=true  → PortraitInverted (phyY counts up, phyBitPos counts down).
+// Both template params are compile-time constants; all ternaries fold away.
+template <GfxRenderer::RenderMode mode, bool inverted>
+static void renderGlyphFast2BitPortrait(uint8_t* const frameBuffer, const uint8_t* const bitmap, const int glyphWidth,
+                                        const int glyphHeight, const int screenXBase, const int screenYBase,
+                                        const bool writeState) {
+  for (int glyphX = 0; glyphX < glyphWidth; glyphX++) {
+    const int phyY = inverted ? (screenXBase + glyphX) : (HalDisplay::DISPLAY_HEIGHT - 1 - (screenXBase + glyphX));
+    if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+    uint8_t* const row = frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES;
+    for (int glyphY = 0; glyphY < glyphHeight; glyphY += 8) {
+      const int count = std::min(8, glyphHeight - glyphY);
+      const uint8_t mask = build2BitColMask<mode>(bitmap, glyphWidth, glyphX, glyphY, count, inverted);
+      if (mask == 0) continue;
+      const int phyBitPos =
+          inverted ? (HalDisplay::DISPLAY_WIDTH - 1 - screenYBase - (glyphY + count - 1)) : (screenYBase + glyphY);
+      if (phyBitPos + count <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+      writeRowBits(row, phyBitPos, mask, writeState);
+    }
+  }
+}
+
+template <GfxRenderer::RenderMode mode>
+static void renderGlyphFast2Bit(uint8_t* const frameBuffer, const uint8_t* const bitmap, const int glyphWidth,
+                                const int glyphHeight, const int screenXBase, const int screenYBase,
+                                const bool pixelState, const GfxRenderer::Orientation orientation) {
+  // Non-rotated text fast path for 2-bit glyphs. Writes compact masks directly to framebuffer rows.
+  // TextRotation::Rotated90CW keeps the legacy per-pixel fallback path for safety and readability.
+  const bool writeState = (mode == GfxRenderer::BW) ? pixelState : false;
+
+  switch (orientation) {
+    case GfxRenderer::LandscapeCounterClockwise: {
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY++) {
+        const int phyY = screenYBase + glyphY;
+        if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+        uint8_t* const row = frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES;
+        const int rowStartPixel = glyphY * glyphWidth;
+        for (int glyphX = 0; glyphX < glyphWidth; glyphX += 8) {
+          const int count = std::min(8, glyphWidth - glyphX);
+          const int pixelStart = rowStartPixel + glyphX;
+          uint8_t mask;
+          if (count == 8 && (pixelStart & 3) == 0) {
+            const int srcByteIdx = pixelStart >> 2;
+            mask = build2BitRowMaskFromTwoBytes<mode>(bitmap[srcByteIdx], bitmap[srcByteIdx + 1]);
+          } else {
+            mask = build2BitRowMask<mode>(bitmap, rowStartPixel, glyphX, count, false);
+          }
+          if (mask == 0) continue;
+          const int phyBitPos = screenXBase + glyphX;
+          if (phyBitPos + count <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+          writeRowBits(row, phyBitPos, mask, writeState);
+        }
+      }
+      break;
+    }
+
+    case GfxRenderer::LandscapeClockwise: {
+      // Row-outer/chunk-inner: framebuffer rows are written at stride -DISPLAY_WIDTH_BYTES
+      // (phyY decreases as glyphY increases). Keeping row-outer preserves sequential access
+      // within each row, which is more cache-friendly than the chunk-outer alternative.
+      for (int glyphY = 0; glyphY < glyphHeight; glyphY++) {
+        const int phyY = HalDisplay::DISPLAY_HEIGHT - 1 - (screenYBase + glyphY);
+        if (phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+        uint8_t* const row = frameBuffer + phyY * HalDisplay::DISPLAY_WIDTH_BYTES;
+        const int rowStartPixel = glyphY * glyphWidth;
+        for (int chunkEnd = glyphWidth - 1; chunkEnd >= 0; chunkEnd -= 8) {
+          const int chunkStart = std::max(0, chunkEnd - 7);
+          const int count = chunkEnd - chunkStart + 1;
+          const int pixelStart = rowStartPixel + chunkStart;
+          uint8_t mask;
+          if (count == 8 && (pixelStart & 3) == 0) {
+            const int srcByteIdx = pixelStart >> 2;
+            mask = reverseBits8(build2BitRowMaskFromTwoBytes<mode>(bitmap[srcByteIdx], bitmap[srcByteIdx + 1]));
+          } else {
+            mask = build2BitRowMask<mode>(bitmap, rowStartPixel, chunkEnd, count, true);
+          }
+          if (mask == 0) continue;
+          const int phyBitPos = HalDisplay::DISPLAY_WIDTH - 1 - screenXBase - chunkEnd;
+          if (phyBitPos + count <= 0 || phyBitPos >= HalDisplay::DISPLAY_WIDTH) continue;
+          writeRowBits(row, phyBitPos, mask, writeState);
+        }
+      }
+      break;
+    }
+
+    case GfxRenderer::Portrait:
+      renderGlyphFast2BitPortrait<mode, false>(frameBuffer, bitmap, glyphWidth, glyphHeight, screenXBase, screenYBase,
+                                               writeState);
+      break;
+
+    case GfxRenderer::PortraitInverted:
+      renderGlyphFast2BitPortrait<mode, true>(frameBuffer, bitmap, glyphWidth, glyphHeight, screenXBase, screenYBase,
+                                              writeState);
+      break;
+  }
+}
+
 // Shared glyph rendering logic for normal and rotated text.
 // Coordinate mapping and cursor advance direction are selected at compile time via the template parameter.
 template <TextRotation rotation>
@@ -97,6 +603,28 @@ static void renderCharImpl(const GfxRenderer& renderer, GfxRenderer::RenderMode
     }
 
     if (is2Bit) {
+      if constexpr (rotation == TextRotation::None) {
+        // Fast path for normal text orientation. Handles all device orientations via renderGlyphFast2Bit.
+        // Dispatch on renderMode at compile time so each specialization gets a constant drawMask.
+        switch (renderMode) {
+          case GfxRenderer::BW:
+            renderGlyphFast2Bit<GfxRenderer::BW>(renderer.getFrameBuffer(), bitmap, width, height, innerBase, outerBase,
+                                                 pixelState, renderer.getOrientation());
+            break;
+          case GfxRenderer::GRAYSCALE_MSB:
+            renderGlyphFast2Bit<GfxRenderer::GRAYSCALE_MSB>(renderer.getFrameBuffer(), bitmap, width, height, innerBase,
+                                                            outerBase, pixelState, renderer.getOrientation());
+            break;
+          case GfxRenderer::GRAYSCALE_LSB:
+            renderGlyphFast2Bit<GfxRenderer::GRAYSCALE_LSB>(renderer.getFrameBuffer(), bitmap, width, height, innerBase,
+                                                            outerBase, pixelState, renderer.getOrientation());
+            break;
+        }
+        *cursorX += glyph->advanceX;
+        return;
+      }
+
+      // Rotated text fallback: keep explicit per-pixel behavior.
       int pixelPosition = 0;
       for (int glyphY = 0; glyphY < height; glyphY++) {
         const int outerCoord = outerBase + glyphY;
@@ -131,6 +659,16 @@ static void renderCharImpl(const GfxRenderer& renderer, GfxRenderer::RenderMode
         }
       }
     } else {
+      // Fast path: 1-bit BW mode, non-rotated text — byte-level framebuffer writes, no drawPixel() per pixel.
+      if constexpr (rotation == TextRotation::None) {
+        if (renderMode == GfxRenderer::BW) {
+          renderGlyphFastBW(renderer.getFrameBuffer(), bitmap, width, height, innerBase, outerBase, pixelState,
+                            renderer.getOrientation());
+          *cursorX += glyph->advanceX;
+          return;
+        }
+      }
+      // Fallback: rotated text or non-BW render mode — per-pixel drawPixel().
       int pixelPosition = 0;
       for (int glyphY = 0; glyphY < height; glyphY++) {
         const int outerCoord = outerBase + glyphY;
@@ -258,6 +796,95 @@ void GfxRenderer::drawText(const int fontId, const int x, const int y, const cha
   }
 }
 
+#ifdef ENABLE_RENDERCHAR_BENCHMARK
+// Legacy per-pixel rendering path — mirrors the old renderCharImpl 1-bit BW loop.
+// Used only by the renderChar benchmark to establish the baseline.
+void GfxRenderer::drawTextBWLegacy(const int fontId, const int x, const int y, const char* text) const {
+  if (text == nullptr || *text == '\0') return;
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) return;
+  const auto& fontFamily = fontIt->second;
+
+  int yPos = y + getFontAscenderSize(fontId);
+  int xPos = x;
+  uint32_t cp;
+  while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&text)))) {
+    const EpdGlyph* glyph = fontFamily.getGlyph(cp, EpdFontFamily::REGULAR);
+    if (!glyph) glyph = fontFamily.getGlyph(REPLACEMENT_GLYPH, EpdFontFamily::REGULAR);
+    if (!glyph) continue;
+    const EpdFontData* fontData = fontFamily.getData(EpdFontFamily::REGULAR);
+    if (fontData->is2Bit) {
+      xPos += glyph->advanceX;
+      continue;
+    }
+    const uint8_t* bitmap = getGlyphBitmap(fontData, glyph);
+    if (bitmap != nullptr) {
+      const int screenYBase = yPos - glyph->top;
+      const int screenXBase = xPos + glyph->left;
+      int pixelPosition = 0;
+      for (int glyphY = 0; glyphY < glyph->height; glyphY++) {
+        for (int glyphX = 0; glyphX < glyph->width; glyphX++, pixelPosition++) {
+          const uint8_t bit = (bitmap[pixelPosition >> 3] >> (7 - (pixelPosition & 7))) & 1;
+          if (!bit) continue;
+          // Inline drawPixel without OOB logging — mirrors the old per-pixel path but clips silently,
+          // matching the fast path's behaviour so the benchmark measures rendering cost only.
+          int phyX, phyY;
+          rotateCoordinates(orientation, screenXBase + glyphX, screenYBase + glyphY, &phyX, &phyY);
+          if (phyX < 0 || phyX >= HalDisplay::DISPLAY_WIDTH || phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+          const uint16_t byteIndex = phyY * HalDisplay::DISPLAY_WIDTH_BYTES + (phyX / 8);
+          const uint8_t bitPosition = 7 - (phyX % 8);
+          frameBuffer[byteIndex] &= ~(1 << bitPosition);  // black pixel
+        }
+      }
+    }
+    xPos += glyph->advanceX;
+  }
+}
+
+// Legacy per-pixel rendering path — mirrors the old renderCharImpl 2-bit BW loop.
+// Used only by the renderChar benchmark to establish the baseline for antialiased fonts.
+void GfxRenderer::drawText2BitLegacy(const int fontId, const int x, const int y, const char* text) const {
+  if (text == nullptr || *text == '\0') return;
+  const auto fontIt = fontMap.find(fontId);
+  if (fontIt == fontMap.end()) return;
+  const auto& fontFamily = fontIt->second;
+
+  int yPos = y + getFontAscenderSize(fontId);
+  int xPos = x;
+  uint32_t cp;
+  while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&text)))) {
+    const EpdGlyph* glyph = fontFamily.getGlyph(cp, EpdFontFamily::REGULAR);
+    if (!glyph) glyph = fontFamily.getGlyph(REPLACEMENT_GLYPH, EpdFontFamily::REGULAR);
+    if (!glyph) continue;
+    const EpdFontData* fontData = fontFamily.getData(EpdFontFamily::REGULAR);
+    if (!fontData->is2Bit) {
+      xPos += glyph->advanceX;
+      continue;
+    }
+    const uint8_t* bitmap = getGlyphBitmap(fontData, glyph);
+    if (bitmap != nullptr) {
+      const int screenYBase = yPos - glyph->top;
+      const int screenXBase = xPos + glyph->left;
+      int pixelPosition = 0;
+      for (int glyphY = 0; glyphY < glyph->height; glyphY++) {
+        for (int glyphX = 0; glyphX < glyph->width; glyphX++, pixelPosition++) {
+          // 2-bit: each pixel occupies 2 bits; MSB first within each byte
+          const uint8_t raw = (bitmap[pixelPosition >> 2] >> (6 - ((pixelPosition & 3) << 1))) & 3;
+          if (!raw) continue;
+          int phyX, phyY;
+          rotateCoordinates(orientation, screenXBase + glyphX, screenYBase + glyphY, &phyX, &phyY);
+          if (phyX < 0 || phyX >= HalDisplay::DISPLAY_WIDTH || phyY < 0 || phyY >= HalDisplay::DISPLAY_HEIGHT) continue;
+          const uint16_t byteIndex = phyY * HalDisplay::DISPLAY_WIDTH_BYTES + (phyX / 8);
+          const uint8_t bitPosition = 7 - (phyX % 8);
+          frameBuffer[byteIndex] &= ~(1 << bitPosition);  // black pixel
+        }
+      }
+    }
+    xPos += glyph->advanceX;
+  }
+}
+#endif  // ENABLE_RENDERCHAR_BENCHMARK
+
 void GfxRenderer::drawLine(int x1, int y1, int x2, int y2, const bool state) const {
   if (x1 == x2) {
     if (y2 < y1) {

lib/GfxRenderer/GfxRenderer.h

@@ -155,4 +155,10 @@ class GfxRenderer {
   // Low level functions
   uint8_t* getFrameBuffer() const;
   static size_t getBufferSize();
+
+#ifdef ENABLE_RENDERCHAR_BENCHMARK
+  // Legacy per-pixel paths — used only by the renderChar benchmark to establish baselines.
+  void drawTextBWLegacy(int fontId, int x, int y, const char* text) const;
+  void drawText2BitLegacy(int fontId, int x, int y, const char* text) const;
+#endif
 };