From 5098cd22a478b7264db9226c996f7fa229fcdb60 Mon Sep 17 00:00:00 2001
From: Sam Atkins <atkinssj@serenityos.org>
Date: Fri, 8 Oct 2021 20:21:46 +0100
Subject: LibWeb: Evaluate `@media` rules

We now evaluate the conditions of `@media` rules at the same point in
the HTML event loop as evaluation of `MediaQueryList`s. This is not
strictly to spec, but since the spec doesn't actually say when to do
this, it seems to make the most sense. In any case, it works! :^)
---
 Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h |  1 +
 Userland/Libraries/LibWeb/CSS/CSSMediaRule.h    |  3 ++-
 Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp   | 30 +++++++++++++++++++++++++
 Userland/Libraries/LibWeb/CSS/CSSRuleList.h     |  1 +
 Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp |  5 +++++
 Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h   |  1 +
 Userland/Libraries/LibWeb/CSS/StyleSheetList.h  |  3 ++-
 Userland/Libraries/LibWeb/DOM/Document.cpp      |  5 +++++
 8 files changed, 47 insertions(+), 2 deletions(-)

(limited to 'Userland')

diff --git a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
index cee8386bfe..127fbbf7a6 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSGroupingRule.h
@@ -22,6 +22,7 @@ public:
     ~CSSGroupingRule();
 
     CSSRuleList const& css_rules() const { return m_rules; }
+    CSSRuleList& css_rules() { return m_rules; }
     size_t insert_rule(StringView const& rule, size_t index = 0);
     void delete_rule(size_t index);
 
diff --git a/Userland/Libraries/LibWeb/CSS/CSSMediaRule.h b/Userland/Libraries/LibWeb/CSS/CSSMediaRule.h
index 4c02dfc08e..be3ce292e3 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSMediaRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSMediaRule.h
@@ -30,11 +30,12 @@ public:
 
     virtual String condition_text() const override;
     virtual void set_condition_text(String) override;
-    // FIXME: We need to evaluate() the query before matches() will work!
     virtual bool condition_matches() const override { return m_media->matches(); }
 
     NonnullRefPtr<MediaList> const& media() const { return m_media; }
 
+    bool evaluate(DOM::Window const& window) { return m_media->evaluate(window); }
+
 private:
     explicit CSSMediaRule(NonnullRefPtr<MediaList>&&, NonnullRefPtrVector<CSSRule>&&);
 
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
index acca567e8a..f1fd30a58b 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp
@@ -126,4 +126,34 @@ bool CSSRuleList::for_first_not_loaded_import_rule(Function<void(CSSImportRule&)
     return false;
 }
 
+void CSSRuleList::evaluate_media_queries(DOM::Window const& window)
+{
+    for (auto& rule : m_rules) {
+        switch (rule.type()) {
+        case CSSRule::Type::Style:
+            break;
+        case CSSRule::Type::Import: {
+            auto& import_rule = verify_cast<CSSImportRule>(rule);
+            if (import_rule.has_import_result())
+                import_rule.loaded_style_sheet()->evaluate_media_queries(window);
+            break;
+        }
+        case CSSRule::Type::Media: {
+            auto& media_rule = verify_cast<CSSMediaRule>(rule);
+            if (media_rule.evaluate(window))
+                media_rule.css_rules().evaluate_media_queries(window);
+            break;
+        }
+        case CSSRule::Type::Supports: {
+            auto& supports_rule = verify_cast<CSSSupportsRule>(rule);
+            if (supports_rule.condition_matches())
+                supports_rule.css_rules().evaluate_media_queries(window);
+            break;
+        }
+        case CSSRule::Type::__Count:
+            VERIFY_NOT_REACHED();
+        }
+    }
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
index 069d67909b..81e773fea2 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSRuleList.h
@@ -53,6 +53,7 @@ public:
 
     void for_each_effective_style_rule(Function<void(CSSStyleRule const&)> const& callback) const;
     bool for_first_not_loaded_import_rule(Function<void(CSSImportRule&)> const& callback);
+    void evaluate_media_queries(DOM::Window const&);
 
 private:
     explicit CSSRuleList(NonnullRefPtrVector<CSSRule>&&);
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
index b7dab97abd..10f1b04d5d 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp
@@ -67,4 +67,9 @@ bool CSSStyleSheet::for_first_not_loaded_import_rule(Function<void(CSSImportRule
     return m_rules->for_first_not_loaded_import_rule(callback);
 }
 
+void CSSStyleSheet::evaluate_media_queries(DOM::Window const& window)
+{
+    m_rules->evaluate_media_queries(window);
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
index dbbf197093..6ff2c2fc05 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h
@@ -46,6 +46,7 @@ public:
 
     void for_each_effective_style_rule(Function<void(CSSStyleRule const&)> const& callback) const;
     bool for_first_not_loaded_import_rule(Function<void(CSSImportRule&)> const& callback);
+    void evaluate_media_queries(DOM::Window const&);
 
 private:
     explicit CSSStyleSheet(NonnullRefPtrVector<CSSRule>);
diff --git a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
index 15e7e8b417..3aa0b63874 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleSheetList.h
@@ -28,7 +28,8 @@ public:
     void add_sheet(NonnullRefPtr<CSSStyleSheet>);
     void remove_sheet(CSSStyleSheet&);
 
-    const NonnullRefPtrVector<CSSStyleSheet>& sheets() const { return m_sheets; }
+    NonnullRefPtrVector<CSSStyleSheet> const& sheets() const { return m_sheets; }
+    NonnullRefPtrVector<CSSStyleSheet>& sheets() { return m_sheets; }
 
     RefPtr<CSSStyleSheet> item(size_t index) const
     {
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index e575c64128..1e20c5b3e2 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -1156,6 +1156,11 @@ void Document::evaluate_media_queries_and_report_changes()
             media_query_list->dispatch_event(event);
         }
     }
+
+    // Also not in the spec, but this is as good a place as any to evaluate @media rules!
+    for (auto& style_sheet : style_sheets().sheets()) {
+        style_sheet.evaluate_media_queries(window());
+    }
 }
 
 }
-- 
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