Method resolveStyle

lib/Epub/Epub/css/CssParser.cpp:633–672

// Style resolution

CssStyle CssParser::resolveStyle(std::string_view tagName, std::string_view classAttr) const {
  static bool lowHeapWarningLogged = false;
  if (ESP.getFreeHeap() < MIN_FREE_HEAP_FOR_CSS) {
    if (!lowHeapWarningLogged) {
      lowHeapWarningLogged = true;
      LOG_DBG("CSS", "Warning: low heap (%u bytes) below MIN_FREE_HEAP_FOR_CSS (%u), returning empty style",
              ESP.getFreeHeap(), static_cast<unsigned>(MIN_FREE_HEAP_FOR_CSS));
    }
    return CssStyle{};
  }

  CssStyle result;

  // 1. Apply element-level style (lowest priority). The map's hash/equal are
  // case-insensitive, so the raw tagName view can be used as the lookup key.
  if (auto it = rulesBySelector_.find(tagName); it != rulesBySelector_.end()) {
    result.applyOver(it->second);
  }

  if (classAttr.empty()) return result;

  // TODO: Support combinations of classes (e.g. style on .class1.class2)
  // 2. Apply class styles (medium priority). The transparent hash/equal accept
  // a CompositeKey, so we never materialize the concatenation.
  forEachDelimitedToken(classAttr, isCssWhitespace, [&](std::string_view cls) {
    if (auto it = rulesBySelector_.find(CompositeKey{".", cls}); it != rulesBySelector_.end()) {
      result.applyOver(it->second);
    }
  });

  // TODO: Support combinations of classes (e.g. style on p.class1.class2)
  // 3. Apply element.class styles (higher priority).
  forEachDelimitedToken(classAttr, isCssWhitespace, [&](std::string_view cls) {
    if (auto it = rulesBySelector_.find(CompositeKey{tagName, ".", cls}); it != rulesBySelector_.end()) {
      result.applyOver(it->second);
    }
  });

  return result;
}

// Inline style parsing (static - doesn't need rule database)