css: Add an always-false media query type

css/media_query.h

@@ -26,6 +26,11 @@ struct Context {
     int window_width{};
 };
 
+struct False {
+    [[nodiscard]] bool operator==(False const &) const = default;
+    constexpr bool evaluate(Context const &) const { return false; }
+};
+
 struct Width {
     int min{};
     int max{std::numeric_limits<int>::max()};
@@ -39,9 +44,10 @@ struct Width {
 class MediaQuery {
 public:
     using Context = detail::Context;
+    using False = detail::False;
     using Width = detail::Width;
 
-    using Query = std::variant<Width>;
+    using Query = std::variant<False, Width>;
     Query query{};
     [[nodiscard]] bool operator==(MediaQuery const &) const = default;
 
@@ -110,6 +116,10 @@ inline std::string to_string(MediaQuery::Width const &width) {
     return std::to_string(width.min) + " <= width <= " + std::to_string(width.max);
 }
 
+constexpr std::string to_string(MediaQuery::False const &) {
+    return "false";
+}
+
 constexpr std::string to_string(MediaQuery const &query) {
     return std::visit([](auto const &q) { return to_string(q); }, query.query);
 }

css/media_query_test.cpp

@@ -55,6 +55,16 @@ void to_string_tests() {
         expect_eq(css::to_string(css::MediaQuery::Width{.min = 299, .max = 301}), //
                 "299 <= width <= 301");
     });
+
+    etest::test("to_string: false", [] {
+        expect_eq(css::to_string(css::MediaQuery::False{}), "false"); //
+    });
+}
+
+void false_tests() {
+    etest::test("false", [] {
+        expect(!css::MediaQuery::False{}.evaluate({.window_width = 299})); //
+    });
 }
 
 void width_tests() {
@@ -91,6 +101,7 @@ void width_tests() {
 int main() {
     parser_tests();
     to_string_tests();
+    false_tests();
     width_tests();
     return etest::run_all_tests();
 }