Function renderCharImpl

lib/GfxRenderer/GfxRenderer.cpp:216–322

template <TextRotation rotation = TextRotation::None>
static void renderCharImpl(const GfxRenderer& renderer, GfxRenderer::RenderMode renderMode,
                           const EpdFontFamily& fontFamily, const uint32_t cp, int cursorX, int cursorY,
                           const bool pixelState, const EpdFontFamily::Style style) {
  const EpdGlyph* glyph = fontFamily.getGlyph(cp, style);
  if (!glyph) {
    LOG_ERR("GFX", "No glyph for codepoint %d", cp);
    return;
  }

  const EpdFontData* fontData = fontFamily.getData(style);
  const bool is2Bit = fontData->is2Bit;
  const uint8_t width = glyph->width;
  const uint8_t height = glyph->height;
  const int left = glyph->left;
  const int top = glyph->top;

  // Tiled-grayscale band culling: if this glyph's physical y-extent is entirely
  // outside the active strip, skip it before the expensive bitmap decode. This
  // is what makes per-band re-rendering cheap. No-op outside strip mode.
  if constexpr (rotation == TextRotation::Rotated90CW) {
    const int ob = cursorX + fontData->ascender - top;
    const int ib = cursorY - left;
    if (!renderer.glyphIntersectsStrip(ob, ib - (width - 1), ob + height - 1, ib)) {
      return;
    }
  } else {
    const int gx0 = cursorX + left;
    const int gy0 = cursorY - top;
    if (!renderer.glyphIntersectsStrip(gx0, gy0, gx0 + width - 1, gy0 + height - 1)) {
      return;
    }
  }

  const uint8_t* bitmap = renderer.getGlyphBitmap(fontData, glyph);

  if (bitmap != nullptr) {
    // For Normal:  outer loop advances screenY, inner loop advances screenX
    // For Rotated: outer loop advances screenX, inner loop advances screenY (in reverse)
    int outerBase, innerBase;
    if constexpr (rotation == TextRotation::Rotated90CW) {
      outerBase = cursorX + fontData->ascender - top;  // screenX = outerBase + glyphY
      innerBase = cursorY - left;                      // screenY = innerBase - glyphX
    } else {
      outerBase = cursorY - top;   // screenY = outerBase + glyphY
      innerBase = cursorX + left;  // screenX = innerBase + glyphX
    }

    if (is2Bit) {
      int pixelPosition = 0;
      for (int glyphY = 0; glyphY < height; glyphY++) {
        const int outerCoord = outerBase + glyphY;
        for (int glyphX = 0; glyphX < width; glyphX++, pixelPosition++) {
          int screenX, screenY;
          if constexpr (rotation == TextRotation::Rotated90CW) {
            screenX = outerCoord;
            screenY = innerBase - glyphX;
          } else {
            screenX = innerBase + glyphX;