LibWeb: Compress specificity into a 32-bit unsigned int

Instead of storing the three-part specificy for every selector,
just mash them together into a 32-bit value instead.
This saves both space and time, and matches the behavior of other
browser engines.

4 files changed, 6 insertions, 68 deletions

diff --git a/Libraries/LibWeb/CSS/Selector.cpp b/Libraries/LibWeb/CSS/Selector.cpp
index 8bc2aafb5e..e5ca4e8962 100644
--- a/Libraries/LibWeb/CSS/Selector.cpp
+++ b/Libraries/LibWeb/CSS/Selector.cpp
@@ -37,7 +37,7 @@ Selector::~Selector()
 {
 }
 
-Specificity Selector::specificity() const
+u32 Selector::specificity() const
 {
     unsigned ids = 0;
     unsigned tag_names = 0;
@@ -61,7 +61,7 @@ Specificity Selector::specificity() const
         }
     }
 
-    return { ids, classes, tag_names };
+    return ids * 0x10000 + classes * 0x100 + tag_names;
 }
 
 }
diff --git a/Libraries/LibWeb/CSS/Selector.h b/Libraries/LibWeb/CSS/Selector.h
index b61285847a..d4be26188a 100644
--- a/Libraries/LibWeb/CSS/Selector.h
+++ b/Libraries/LibWeb/CSS/Selector.h
@@ -91,7 +91,7 @@ public:
 
     const Vector<ComplexSelector>& complex_selectors() const { return m_complex_selectors; }
 
-    Specificity specificity() const;
+    u32 specificity() const;
 
 private:
     Vector<ComplexSelector> m_complex_selectors;
diff --git a/Libraries/LibWeb/CSS/Specificity.h b/Libraries/LibWeb/CSS/Specificity.h
deleted file mode 100644
index 30e7b3c7d5..0000000000
--- a/Libraries/LibWeb/CSS/Specificity.h
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this
- *    list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice,
- *    this list of conditions and the following disclaimer in the documentation
- *    and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#pragma once
-
-namespace Web {
-
-class Specificity {
-public:
-    Specificity(unsigned ids, unsigned classes, unsigned tag_names)
-        : m_ids(ids)
-        , m_classes(classes)
-        , m_tag_names(tag_names)
-    {
-    }
-
-    unsigned ids() const { return m_ids; }
-    unsigned classes() const { return m_classes; }
-    unsigned tag_names() const { return m_tag_names; }
-
-    bool operator<(const Specificity& other) const
-    {
-        return m_ids < other.m_ids
-            || m_classes < other.m_classes
-            || m_tag_names < other.m_tag_names;
-    }
-
-    bool operator==(const Specificity& other) const
-    {
-        return m_ids == other.m_ids
-            || m_classes == other.m_classes
-            || m_tag_names == other.m_tag_names;
-    }
-
-private:
-    unsigned m_ids { 0 };
-    unsigned m_classes { 0 };
-    unsigned m_tag_names { 0 };
-};
-
-}
diff --git a/Libraries/LibWeb/CSS/StyleResolver.cpp b/Libraries/LibWeb/CSS/StyleResolver.cpp
index 142a100342..2d74c34ddd 100644
--- a/Libraries/LibWeb/CSS/StyleResolver.cpp
+++ b/Libraries/LibWeb/CSS/StyleResolver.cpp
@@ -497,12 +497,14 @@ NonnullRefPtr<StyleProperties> StyleResolver::resolve_style(const Element& eleme
     quick_sort(matching_rules, [&](MatchingRule& a, MatchingRule& b) {
         auto& a_selector = a.rule->selectors()[a.selector_index];
         auto& b_selector = b.rule->selectors()[b.selector_index];
+        auto a_specificity = a_selector.specificity();
+        auto b_specificity = b_selector.specificity();
         if (a_selector.specificity() == b_selector.specificity()) {
             if (a.style_sheet_index == b.style_sheet_index)
                 return a.rule_index < b.rule_index;
             return a.style_sheet_index < b.style_sheet_index;
         }
-        return a_selector.specificity() < b_selector.specificity();
+        return a_specificity < b_specificity;
     });
 
     for (auto& match : matching_rules) {