LibWeb: Port the CSS namespace to IDL

Userland/Libraries/LibWeb/CSS/CSS.cpp

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/VM.h>
+#include <LibWeb/CSS/CSS.h>
+#include <LibWeb/CSS/Parser/Parser.h>
+#include <LibWeb/CSS/PropertyID.h>
+#include <LibWeb/CSS/Serialize.h>
+
+namespace Web::CSS {
+
+// https://www.w3.org/TR/cssom-1/#dom-css-escape
+WebIDL::ExceptionOr<String> escape(JS::VM& vm, StringView identifier)
+{
+    // The escape(ident) operation must return the result of invoking serialize an identifier of ident.
+    return TRY_OR_THROW_OOM(vm, serialize_an_identifier(identifier));
+}
+
+// https://www.w3.org/TR/css-conditional-3/#dom-css-supports
+bool supports(JS::VM& vm, StringView property, StringView value)
+{
+    auto& realm = *vm.current_realm();
+
+    // 1. If property is an ASCII case-insensitive match for any defined CSS property that the UA supports,
+    //    and value successfully parses according to that property’s grammar, return true.
+    if (auto property_id = property_id_from_string(property); property_id != PropertyID::Invalid) {
+        if (parse_css_value(Parser::ParsingContext { realm }, value, property_id))
+            return true;
+    }
+
+    // 2. Otherwise, if property is a custom property name string, return true.
+    // FIXME: This check is not enough to make sure this is a valid custom property name, but it's close enough.
+    else if (property.starts_with("--"sv) && property.length() >= 3) {
+        return true;
+    }
+
+    // 3. Otherwise, return false.
+    return false;
+}
+
+// https://www.w3.org/TR/css-conditional-3/#dom-css-supports
+WebIDL::ExceptionOr<bool> supports(JS::VM& vm, StringView condition_text)
+{
+    auto& realm = *vm.current_realm();
+
+    // 1. If conditionText, parsed and evaluated as a <supports-condition>, would return true, return true.
+    if (auto supports = parse_css_supports(Parser::ParsingContext { realm }, condition_text); supports && supports->matches())
+        return true;
+
+    // 2. Otherwise, If conditionText, wrapped in parentheses and then parsed and evaluated as a <supports-condition>, would return true, return true.
+    auto wrapped_condition_text = TRY_OR_THROW_OOM(vm, String::formatted("({})", condition_text));
+
+    if (auto supports = parse_css_supports(Parser::ParsingContext { realm }, wrapped_condition_text); supports && supports->matches())
+        return true;
+
+    // 3. Otherwise, return false.
+    return false;
+}
+
+}