From e5fbaa5d69d1d11aa50ed80fd497685b05c58909 Mon Sep 17 00:00:00 2001
From: Nicolas Chevobbe <nchevobbe@mozilla.com>
Date: Thu, 15 Feb 2024 14:04:32 +0000
Subject: [PATCH] Bug 1247751 - [devtools] Add InspectorUtils.getRuleIndex.
 r=emilio,devtools-reviewers,ochameau.

Differential Revision: https://phabricator.services.mozilla.com/D201383
---
 devtools/server/actors/style-rule.js          | 31 +------
 dom/chrome-webidl/InspectorUtils.webidl       |  1 +
 layout/inspector/InspectorUtils.cpp           | 45 ++++++++++
 layout/inspector/InspectorUtils.h             |  3 +
 layout/inspector/tests/mochitest.toml         |  2 +
 layout/inspector/tests/test_getRuleIndex.html | 88 +++++++++++++++++++
 6 files changed, 141 insertions(+), 29 deletions(-)
 create mode 100644 layout/inspector/tests/test_getRuleIndex.html

diff --git a/devtools/server/actors/style-rule.js b/devtools/server/actors/style-rule.js
index 512279c17cfe..e9f39fa3d067 100644
--- a/devtools/server/actors/style-rule.js
+++ b/devtools/server/actors/style-rule.js
@@ -611,35 +611,8 @@ class StyleRuleActor extends Actor {
    * nested rules.
    */
   _computeRuleIndex() {
-    let rule = this.rawRule;
-    const result = [];
-
-    while (rule) {
-      let cssRules = [];
-      if (rule.parentRule) {
-        cssRules = rule.parentRule.cssRules;
-      } else if (rule.parentStyleSheet) {
-        cssRules = rule.parentStyleSheet.cssRules;
-      }
-
-      let found = false;
-      for (let i = 0; i < cssRules.length; i++) {
-        if (rule === cssRules.item(i)) {
-          found = true;
-          result.unshift(i);
-          break;
-        }
-      }
-
-      if (!found) {
-        this._ruleIndex = null;
-        return;
-      }
-
-      rule = rule.parentRule;
-    }
-
-    this._ruleIndex = result;
+    const index = InspectorUtils.getRuleIndex(this.rawRule);
+    this._ruleIndex = index.length ? index : null;
   }
 
   /**
diff --git a/dom/chrome-webidl/InspectorUtils.webidl b/dom/chrome-webidl/InspectorUtils.webidl
index 5d785e8051b2..e3ca8a3b51a3 100644
--- a/dom/chrome-webidl/InspectorUtils.webidl
+++ b/dom/chrome-webidl/InspectorUtils.webidl
@@ -21,6 +21,7 @@ namespace InspectorUtils {
   unsigned long getRuleLine(CSSRule rule);
   unsigned long getRuleColumn(CSSRule rule);
   unsigned long getRelativeRuleLine(CSSRule rule);
+  sequence<unsigned long> getRuleIndex(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
diff --git a/layout/inspector/InspectorUtils.cpp b/layout/inspector/InspectorUtils.cpp
index acebb863066c..e2111aa9bd04 100644
--- a/layout/inspector/InspectorUtils.cpp
+++ b/layout/inspector/InspectorUtils.cpp
@@ -32,6 +32,7 @@
 #include "mozilla/dom/CSSBinding.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/CSSStyleRule.h"
+#include "mozilla/dom/CSSKeyframesRule.h"
 #include "mozilla/dom/Highlight.h"
 #include "mozilla/dom/HighlightRegistry.h"
 #include "mozilla/dom/InspectorUtilsBinding.h"
@@ -350,6 +351,50 @@ uint32_t InspectorUtils::GetRelativeRuleLine(GlobalObject& aGlobal,
   return aRule.GetLineNumber() + 1;
 }
 
+
+void InspectorUtils::GetRuleIndex(GlobalObject& aGlobal,
+                                  css::Rule& aRule,
+                                  nsTArray<uint32_t>& aResult) {
+  css::Rule* currentRule = &aRule;
+
+  do {
+    css::Rule* parentRule = currentRule->GetParentRule();
+    dom::CSSRuleList* ruleList = nullptr;
+
+    if (parentRule) {
+      if (parentRule->IsGroupRule()) {
+        ruleList = static_cast<css::GroupRule*>(parentRule)->CssRules();
+      } else if (parentRule->Type() == StyleCssRuleType::Keyframes) {
+        ruleList = static_cast<CSSKeyframesRule*>(parentRule)->CssRules();
+      } else {
+        MOZ_ASSERT_UNREACHABLE("Unknown parent rule type?");
+      }
+    } else if (StyleSheet* sheet = currentRule->GetStyleSheet()) {
+      ruleList = sheet->GetCssRulesInternal();
+    }
+
+    if (!ruleList) {
+      return;
+    }
+
+    bool found = false;
+    for (uint32_t i = 0, len = ruleList->Length(); i < len; ++i) {
+      css::Rule* rule = ruleList->Item(i);
+      if (currentRule == rule) {
+        found = true;
+        aResult.InsertElementAt(0, i);
+        break;
+      }
+    }
+
+    if (!found) {
+      return;
+    }
+
+    currentRule = parentRule;
+  } while (currentRule);
+}
+
 /* static */
 bool InspectorUtils::HasRulesModifiedByCSSOM(GlobalObject& aGlobal,
                                              StyleSheet& aSheet) {
diff --git a/layout/inspector/InspectorUtils.h b/layout/inspector/InspectorUtils.h
index ef841eefdf0f..06bc0ff5fce5 100644
--- a/layout/inspector/InspectorUtils.h
+++ b/layout/inspector/InspectorUtils.h
@@ -72,6 +72,9 @@ class InspectorUtils {
    */
   static uint32_t GetRelativeRuleLine(GlobalObject& aGlobal, css::Rule& aRule);
 
+  static void GetRuleIndex(GlobalObject& aGlobal, css::Rule& aRule,
+                           nsTArray<uint32_t>& aResult);
+
   static bool HasRulesModifiedByCSSOM(GlobalObject& aGlobal,
                                       StyleSheet& aSheet);
 
diff --git a/layout/inspector/tests/mochitest.toml b/layout/inspector/tests/mochitest.toml
index 9c9ba8e60a57..3db9693c2073 100644
--- a/layout/inspector/tests/mochitest.toml
+++ b/layout/inspector/tests/mochitest.toml
@@ -58,6 +58,8 @@ support-files = [
 
 ["test_getRelativeRuleLine.html"]
 
+["test_getRuleIndex.html"]
+
 ["test_get_all_style_sheets.html"]
 
 ["test_is_element_themed.html"]
diff --git a/layout/inspector/tests/test_getRuleIndex.html b/layout/inspector/tests/test_getRuleIndex.html
new file mode 100644
index 000000000000..0eb9dba27b65
--- /dev/null
+++ b/layout/inspector/tests/test_getRuleIndex.html
@@ -0,0 +1,88 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test InspectorUtils.getRuleIndex</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <style>
+    @property --color {
+      syntax: "*";
+      inherits: false;
+    }
+    html {
+      background: gold;
+
+      &:hover {
+        background: yellow;
+      }
+
+      & body {
+        color: tomato;
+
+        &:focus-visible {
+          outline: 1px solid cyan;
+        }
+      }
+    }
+    @keyframes anim {
+      0% {
+        color: blue;
+      }
+      100% {
+        color: green;
+      }
+    }
+  </style>
+</head>
+<body>
+<code>InspectorUtils.getRuleIndex</code>
+
+<script>
+"use strict";
+
+/** Test for InspectorUtils.getCSSRegisteredProperties **/
+
+const { Assert } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://testing-common/Assert.sys.mjs"
+);
+const InspectorUtils = SpecialPowers.InspectorUtils;
+
+const stylesheet = document.styleSheets[1];
+const stylesheetRules = stylesheet.cssRules;
+
+let rule = stylesheetRules[0];
+is(rule.name, "--color", "Expected @property rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [0]);
+
+rule = stylesheetRules[1];
+is(rule.selectorText, "html", "Expected htlm rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [1]);
+
+rule = stylesheetRules[1].cssRules[0];
+is(rule.selectorText, "&:hover", "Expected nested &:hover rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [1, 0]);
+
+rule = stylesheetRules[1].cssRules[1];
+is(rule.selectorText, "& body", "Expected nested & body rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [1, 1]);
+
+rule = stylesheetRules[1].cssRules[1].cssRules[0];
+is(rule.selectorText, "&:focus-visible", "Expected nested &:focus-visible rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [1, 1, 0]);
+
+rule = stylesheetRules[2];
+is(rule.name, "anim", "Expected @keyframes rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [2]);
+
+rule = stylesheetRules[2].cssRules[0];
+is(rule.keyText, "0%", "Expected 0% keyframe rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [2, 0]);
+
+rule = stylesheetRules[2].cssRules[1];
+is(rule.keyText, "100%", "Expected 100% keyframe rule");
+Assert.deepEqual(InspectorUtils.getRuleIndex(rule), [2, 1]);
+
+</script>
+</pre>
+</body>
+</html>