Bug 1839168 - [devtools] Add `InspectorUtils.getAllStyleSheetCSSStyleRules` method. r=emilio.

This method returns a flat list of all the rules in a given stylesheet.
This will be helpful for DevTools so we don't have to recursively walk through
all the children rules (which is slow on the JS DevTools server).

Differential Revision: https://phabricator.services.mozilla.com/D181505

dom/chrome-webidl/InspectorUtils.webidl

@@ -22,6 +22,10 @@ namespace InspectorUtils {
   unsigned long getRuleColumn(CSSRule rule);
   unsigned long getRelativeRuleLine(CSSRule rule);
   boolean hasRulesModifiedByCSSOM(CSSStyleSheet sheet);
+  // Get a flat list of all rules (including nested ones) of a given stylesheet.
+  // Useful for DevTools as this is faster than in JS where we'd have a lot of
+  // proxy access overhead building the same list.
+  sequence<CSSRule> getAllStyleSheetCSSStyleRules(CSSStyleSheet sheet);
   boolean isInheritedProperty(UTF8String property);
   sequence<DOMString> getCSSPropertyNames(optional PropertyNamesOptions options = {});
   sequence<PropertyPref> getCSSPropertyPrefs();

layout/inspector/InspectorUtils.cpp

@@ -364,6 +364,23 @@ bool InspectorUtils::HasRulesModifiedByCSSOM(GlobalObject& aGlobal,
   return aSheet.HasModifiedRulesForDevtools();
 }
 
+static void CollectRules(ServoCSSRuleList& aRuleList,
+                         nsTArray<RefPtr<css::Rule>>& aResult) {
+  for (uint32_t i = 0, len = aRuleList.Length(); i < len; ++i) {
+    css::Rule* rule = aRuleList.GetRule(i);
+    aResult.AppendElement(rule);
+    if (rule->IsGroupRule()) {
+      CollectRules(*static_cast<css::GroupRule*>(rule)->CssRules(), aResult);
+    }
+  }
+}
+
+void InspectorUtils::GetAllStyleSheetCSSStyleRules(
+    GlobalObject& aGlobal, StyleSheet& aSheet,
+    nsTArray<RefPtr<css::Rule>>& aResult) {
+  CollectRules(*aSheet.GetCssRulesInternal(), aResult);
+}
+
 /* static */
 bool InspectorUtils::IsInheritedProperty(GlobalObject& aGlobalObject,
                                          const nsACString& aPropertyName) {

layout/inspector/InspectorUtils.h

@@ -75,6 +75,10 @@ class InspectorUtils {
   static bool HasRulesModifiedByCSSOM(GlobalObject& aGlobal,
                                       StyleSheet& aSheet);
 
+  static void GetAllStyleSheetCSSStyleRules(
+      GlobalObject& aGlobal, StyleSheet& aSheet,
+      nsTArray<RefPtr<css::Rule>>& aResult);
+
   // Utilities for working with CSS properties
   //
   // Returns true if the string names a property that is inherited by default.

layout/style/GroupRule.h

@@ -44,6 +44,8 @@ class GroupRule : public Rule {
   GroupRule(const GroupRule&) = delete;
   bool IsCCLeaf() const override;
 
+  bool IsGroupRule() const final { return true; }
+
 #ifdef DEBUG
   void List(FILE* out = stdout, int32_t aIndent = 0) const override;
 #endif

layout/style/Rule.h

@@ -58,6 +58,8 @@ class Rule : public nsISupports, public nsWrapperCache {
   // sense that it doesn't have any outgoing owning edges.
   virtual bool IsCCLeaf() const MOZ_MUST_OVERRIDE;
 
+  virtual bool IsGroupRule() const { return false; }
+
 #ifdef DEBUG
   virtual void List(FILE* out = stdout, int32_t aIndent = 0) const = 0;
 #endif