LibWeb: Implement the translate attribute

Author: https://github.com/Calme1709
Commit: 279913a223
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4855
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/DOM/Element.cpp

@@ -3327,6 +3327,36 @@ IntersectionObserver::IntersectionObserverRegistration& Element::get_intersectio
     return *registration_iterator;
 }
 
+// https://html.spec.whatwg.org/multipage/dom.html#translation-mode
+Element::TranslationMode Element::translation_mode() const
+{
+    // Each element (even non-HTML elements) has a translation mode, which is in either the translate-enabled state or
+    // the no-translate state.
+
+    // If an HTML element's translate attribute is in the Yes state, then the element's translation mode is in the
+    // translate-enabled state;
+    // NOTE: The attribute is in the Yes state if the attribute is present and its value is the empty string or is a
+    //       ASCII-case-insensitive match for "yes".
+    auto maybe_translate_attribute = attribute(HTML::AttributeNames::translate);
+    if (maybe_translate_attribute.has_value() && (maybe_translate_attribute.value().is_empty() || maybe_translate_attribute.value().equals_ignoring_ascii_case("yes"sv)))
+        return TranslationMode::TranslateEnabled;
+
+    // otherwise, if the element's translate attribute is in the No state, then the element's translation mode is in
+    // the no-translate state.
+    if (maybe_translate_attribute.has_value() && maybe_translate_attribute.value().equals_ignoring_ascii_case("no"sv)) {
+        return TranslationMode::NoTranslate;
+    }
+
+    // Otherwise, either the element's translate attribute is in the Inherit state, or the element is not an HTML
+    // element and thus does not have a translate attribute; in either case, the element's translation mode is in the
+    // same state as its parent element's, if any.
+    if (auto parent = parent_element())
+        return parent->translation_mode();
+
+    // or in the translate-enabled state, if the element's parent element is null
+    return TranslationMode::TranslateEnabled;
+}
+
 // https://html.spec.whatwg.org/multipage/dom.html#the-directionality
 Element::Directionality Element::directionality() const
 {