LibWeb: Implement MediaQuery matching :^)

Currently, `evaluate()` recalculates whether the MediaQuery matches or
not, and stores it in `m_matches`, which users can query using
`matches()`. This allows us to know when the match-state changes, which
is required to fire MediaQueryList's change event.

Userland/Libraries/LibWeb/CSS/MediaQuery.cpp

@@ -5,6 +5,8 @@
  */
 
 #include <LibWeb/CSS/MediaQuery.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/Window.h>
 
 namespace Web::CSS {
 
@@ -33,6 +35,59 @@ String MediaQuery::MediaFeature::to_string() const
     VERIFY_NOT_REACHED();
 }
 
+bool MediaQuery::MediaFeature::evaluate(DOM::Window const& window) const
+{
+    auto queried_value = window.query_media_feature(name);
+    if (!queried_value)
+        return false;
+
+    switch (type) {
+    case Type::IsTrue:
+        if (queried_value->has_number())
+            return queried_value->to_number() != 0;
+        if (queried_value->has_length())
+            return queried_value->to_length().raw_value() != 0;
+        if (queried_value->has_identifier())
+            return queried_value->to_identifier() != ValueID::None;
+        return false;
+
+    case Type::ExactValue:
+        return queried_value->equals(*value);
+
+    case Type::MinValue:
+        if (queried_value->has_number() && value->has_number())
+            return queried_value->to_number() >= value->to_number();
+        if (queried_value->has_length() && value->has_length()) {
+            auto queried_length = queried_value->to_length();
+            auto value_length = value->to_length();
+            // FIXME: We should be checking that lengths are valid during parsing
+            if (!value_length.is_absolute()) {
+                dbgln("Media feature was given a non-absolute length, which is invalid! {}", value_length.to_string());
+                return false;
+            }
+            return queried_length.absolute_length_to_px() >= value_length.absolute_length_to_px();
+        }
+        return false;
+
+    case Type::MaxValue:
+        if (queried_value->has_number() && value->has_number())
+            return queried_value->to_number() <= value->to_number();
+        if (queried_value->has_length() && value->has_length()) {
+            auto queried_length = queried_value->to_length();
+            auto value_length = value->to_length();
+            // FIXME: We should be checking that lengths are valid during parsing
+            if (!value_length.is_absolute()) {
+                dbgln("Media feature was given a non-absolute length, which is invalid! {}", value_length.to_string());
+                return false;
+            }
+            return queried_length.absolute_length_to_px() <= value_length.absolute_length_to_px();
+        }
+        return false;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
 String MediaQuery::MediaCondition::to_string() const
 {
     StringBuilder builder;
@@ -56,6 +111,33 @@ String MediaQuery::MediaCondition::to_string() const
     return builder.to_string();
 }
 
+bool MediaQuery::MediaCondition::evaluate(DOM::Window const& window) const
+{
+    switch (type) {
+    case Type::Single:
+        return feature.evaluate(window);
+
+    case Type::Not:
+        return !conditions.first().evaluate(window);
+
+    case Type::And:
+        for (auto& child : conditions) {
+            if (!child.evaluate(window))
+                return false;
+        }
+        return true;
+
+    case Type::Or:
+        for (auto& child : conditions) {
+            if (child.evaluate(window))
+                return true;
+        }
+        return false;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
 String MediaQuery::to_string() const
 {
     StringBuilder builder;
@@ -110,4 +192,39 @@ String MediaQuery::to_string() const
     return builder.to_string();
 }
 
+bool MediaQuery::evaluate(DOM::Window const& window)
+{
+    auto matches_media = [](MediaType media) -> bool {
+        switch (media) {
+        case MediaType::All:
+            return true;
+        case MediaType::Print:
+            // FIXME: Enable for printing, when we have printing!
+            return false;
+        case MediaType::Screen:
+            // FIXME: Disable for printing, when we have printing!
+            return true;
+        // Deprecated, must never match:
+        case MediaType::TTY:
+        case MediaType::TV:
+        case MediaType::Projection:
+        case MediaType::Handheld:
+        case MediaType::Braille:
+        case MediaType::Embossed:
+        case MediaType::Aural:
+        case MediaType::Speech:
+            return false;
+        }
+        VERIFY_NOT_REACHED();
+    };
+
+    bool result = matches_media(m_media_type);
+
+    if (result && m_media_condition)
+        result = m_media_condition->evaluate(window);
+
+    m_matches = m_negated ? !result : result;
+    return m_matches;
+}
+
 }