From dfe44b58d5f5c3dda92e283eff05887e07eb2ba3 Mon Sep 17 00:00:00 2001
From: Olli Pettay <Olli.Pettay@helsinki.fi>
Date: Tue, 11 Apr 2023 09:24:21 +0000
Subject: [PATCH] Bug 1819769 - don't dispatch a11y related events when there
 are no listeners, r=masayuki

Differential Revision: https://phabricator.services.mozilla.com/D175016
---
 dom/base/nsContentUtils.cpp         |  3 +++
 dom/base/nsContentUtils.h           | 19 +++++++++++++++++++
 dom/events/EventListenerManager.cpp |  6 ++++++
 dom/html/HTMLInputElement.cpp       |  6 ++++--
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index e0458cc3e453..2d62488d0220 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -466,6 +466,9 @@ nsParser* nsContentUtils::sXMLFragmentParser = nullptr;
 nsIFragmentContentSink* nsContentUtils::sXMLFragmentSink = nullptr;
 bool nsContentUtils::sFragmentParsingActive = false;
 
+bool nsContentUtils::sMayHaveFormCheckboxStateChangeListeners = false;
+bool nsContentUtils::sMayHaveFormRadioStateChangeListeners = false;
+
 mozilla::LazyLogModule nsContentUtils::gResistFingerprintingLog(
     "nsResistFingerprinting");
 mozilla::LazyLogModule nsContentUtils::sDOMDumpLog("Dump");
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index fc0eb7adef33..6b517e2fb1a1 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -3373,6 +3373,22 @@ class nsContentUtils {
    */
   static void RequestGeckoTaskBurst();
 
+  static void SetMayHaveFormCheckboxStateChangeListeners() {
+    sMayHaveFormCheckboxStateChangeListeners = true;
+  }
+
+  static bool MayHaveFormCheckboxStateChangeListeners() {
+    return sMayHaveFormCheckboxStateChangeListeners;
+  }
+
+  static void SetMayHaveFormRadioStateChangeListeners() {
+    sMayHaveFormRadioStateChangeListeners = true;
+  }
+
+  static bool MayHaveFormRadioStateChangeListeners() {
+    return sMayHaveFormRadioStateChangeListeners;
+  }
+
  private:
   static bool InitializeEventTable();
 
@@ -3493,6 +3509,9 @@ class nsContentUtils {
 
   static int32_t sInnerOrOuterWindowCount;
   static uint32_t sInnerOrOuterWindowSerialCounter;
+
+  static bool sMayHaveFormCheckboxStateChangeListeners;
+  static bool sMayHaveFormRadioStateChangeListeners;
 };
 
 /* static */ inline ExtContentPolicyType
diff --git a/dom/events/EventListenerManager.cpp b/dom/events/EventListenerManager.cpp
index 92a779ed8e5c..6ad9577de765 100644
--- a/dom/events/EventListenerManager.cpp
+++ b/dom/events/EventListenerManager.cpp
@@ -472,6 +472,12 @@ void EventListenerManager::AddEventListenerInternal(
           window->SetHasTransitionEventListeners();
         }
         break;
+      case eFormCheckboxStateChange:
+        nsContentUtils::SetMayHaveFormCheckboxStateChangeListeners();
+        break;
+      case eFormRadioStateChange:
+        nsContentUtils::SetMayHaveFormRadioStateChangeListeners();
+        break;
       default:
         // XXX Use NS_ASSERTION here to print resolvedEventMessage since
         //     MOZ_ASSERT can take only string literal, not pointer to
diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index 3f7e20e43a9b..7d7d7a93b6d8 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -3728,8 +3728,10 @@ nsresult HTMLInputElement::PostHandleEvent(EventChainPostVisitor& aVisitor) {
 #ifdef ACCESSIBILITY
       // Fire an event to notify accessibility
       if (mType == FormControlType::InputCheckbox) {
-        FireEventForAccessibility(this, eFormCheckboxStateChange);
-      } else {
+        if (nsContentUtils::MayHaveFormCheckboxStateChangeListeners()) {
+          FireEventForAccessibility(this, eFormCheckboxStateChange);
+        }
+      } else if (nsContentUtils::MayHaveFormRadioStateChangeListeners()) {
         FireEventForAccessibility(this, eFormRadioStateChange);
         // Fire event for the previous selected radio.
         nsCOMPtr<nsIContent> content = do_QueryInterface(aVisitor.mItemData);