LibHTML: Implement basic style inheritance

Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/841ae443923
Pull-request: https://github.com/SerenityOS/serenity/pull/609
Reviewed-by: https://github.com/awesomekling ✅

Libraries/LibHTML/CSS/StyleResolver.cpp

@@ -52,9 +52,18 @@ NonnullRefPtrVector<StyleRule> StyleResolver::collect_matching_rules(const Eleme
     return matching_rules;
 }
 
-StyleProperties StyleResolver::resolve_style(const Element& element)
+StyleProperties StyleResolver::resolve_style(const Element& element, const StyleProperties* parent_properties) const
 {
     StyleProperties style_properties;
+
+    if (parent_properties) {
+        parent_properties->for_each_property([&](const StringView& name, auto& value) {
+            // TODO: proper inheritance
+            if (name.starts_with("font") || name == "white-space")
+                style_properties.set_property(name, value);
+        });
+    }
+
     auto matching_rules = collect_matching_rules(element);
     for (auto& rule : matching_rules) {
         for (auto& declaration : rule.declarations()) {

Libraries/LibHTML/CSS/StyleResolver.h

@@ -18,7 +18,7 @@ public:
     Document& document() { return m_document; }
     const Document& document() const { return m_document; }
 
-    StyleProperties resolve_style(const Element&);
+    StyleProperties resolve_style(const Element&, const StyleProperties* parent_properties) const;
 
     NonnullRefPtrVector<StyleRule> collect_matching_rules(const Element&) const;