Bug 1771113 - Add chromeOnly StyleSheetRemoved event, emitted when a stylesheet is removed. r=emilio.

This new event will be consumed by DevTools to update style information.

As for `StyleSheetApplicableStateChanged`, this event is emitted from the document.
It's only enabled when `document.styleSheetChangeEventsEnabled` is set to true.

The existing test around the `StyleSheetApplicableStateChanged` is renamed and
modified to assert both events when stylesheets are added, modified and removed.

Differential Revision: https://phabricator.services.mozilla.com/D147271

.stylelintignore

@@ -66,7 +66,7 @@ dom/xml/test/old/toc/book.css
 dom/xml/test/old/toc/toc.css
 
 # Tests we don't want to modify at this point:
-layout/base/tests/bug839103.css
+layout/base/tests/stylesheet_change_events.css
 layout/inspector/tests/bug856317.css
 layout/inspector/tests/chrome/test_bug467669.css
 layout/inspector/tests/chrome/test_bug708874.css

dom/base/Document.cpp

@@ -225,6 +225,8 @@
 #include "mozilla/dom/StyleSheetApplicableStateChangeEvent.h"
 #include "mozilla/dom/StyleSheetApplicableStateChangeEventBinding.h"
 #include "mozilla/dom/StyleSheetList.h"
+#include "mozilla/dom/StyleSheetRemovedEvent.h"
+#include "mozilla/dom/StyleSheetRemovedEventBinding.h"
 #include "mozilla/dom/TimeoutManager.h"
 #include "mozilla/dom/ToggleEvent.h"
 #include "mozilla/dom/Touch.h"
@@ -7450,6 +7452,26 @@ void Document::PostStyleSheetApplicableStateChangeEvent(StyleSheet& aSheet) {
   asyncDispatcher->PostDOMEvent();
 }
 
+void Document::PostStyleSheetRemovedEvent(StyleSheet& aSheet) {
+  if (!StyleSheetChangeEventsEnabled()) {
+    return;
+  }
+
+  StyleSheetRemovedEventInit init;
+  init.mBubbles = true;
+  init.mCancelable = false;
+  init.mStylesheet = &aSheet;
+
+  RefPtr<StyleSheetRemovedEvent> event =
+      StyleSheetRemovedEvent::Constructor(this, u"StyleSheetRemoved"_ns, init);
+  event->SetTrusted(true);
+  event->SetTarget(this);
+  RefPtr<AsyncEventDispatcher> asyncDispatcher =
+      new AsyncEventDispatcher(this, event);
+  asyncDispatcher->mOnlyChromeDispatch = ChromeOnlyDispatch::eYes;
+  asyncDispatcher->PostDOMEvent();
+}
+
 static int32_t FindSheet(const nsTArray<RefPtr<StyleSheet>>& aSheets,
                          nsIURI* aSheetURI) {
   for (int32_t i = aSheets.Length() - 1; i >= 0; i--) {

dom/base/Document.h

@@ -1687,8 +1687,8 @@ class Document : public nsINode,
    * and that observers should be notified and style sets updated
    */
   void StyleSheetApplicableStateChanged(StyleSheet&);
-
   void PostStyleSheetApplicableStateChangeEvent(StyleSheet&);
+  void PostStyleSheetRemovedEvent(StyleSheet&);
 
   enum additionalSheetType {
     eAgentSheet,

dom/base/DocumentOrShadowRoot.cpp

@@ -93,6 +93,7 @@ void DocumentOrShadowRoot::RemoveStyleSheet(StyleSheet& aSheet) {
   mStyleSheets.RemoveElementAt(index);
   RemoveSheetFromStylesIfApplicable(*sheet);
   sheet->ClearAssociatedDocumentOrShadowRoot();
+  AsNode().OwnerDoc()->PostStyleSheetRemovedEvent(aSheet);
 }
 
 void DocumentOrShadowRoot::RemoveSheetFromStylesIfApplicable(

dom/chrome-webidl/StyleSheetRemovedEvent.webidl

@@ -0,0 +1,17 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+[ChromeOnly, Exposed=Window]
+interface StyleSheetRemovedEvent : Event {
+  constructor(DOMString type,
+              optional StyleSheetRemovedEventInit eventInitDict = {});
+
+  readonly attribute CSSStyleSheet? stylesheet;
+};
+
+dictionary StyleSheetRemovedEventInit : EventInit {
+  CSSStyleSheet? stylesheet = null;
+};

dom/chrome-webidl/moz.build

@@ -81,6 +81,8 @@ WEBIDL_FILES = [
     "SessionStoreUtils.webidl",
     "StripOnShareRule.webidl",
     "StructuredCloneHolder.webidl",
+    "StyleSheetApplicableStateChangeEvent.webidl",
+    "StyleSheetRemovedEvent.webidl",
     "TelemetryStopwatch.webidl",
     "UserInteraction.webidl",
     "WebExtensionContentScript.webidl",
@@ -92,6 +94,11 @@ WEBIDL_FILES = [
     "XULTreeElement.webidl",
 ]
 
+GENERATED_EVENTS_WEBIDL_FILES = [
+    "StyleSheetApplicableStateChangeEvent.webidl",
+    "StyleSheetRemovedEvent.webidl",
+]
+
 if CONFIG["MOZ_BUILD_APP"] != "mobile/android":
     WEBIDL_FILES += [
         "UniFFI.webidl",

dom/events/test/test_all_synthetic_events.html

@@ -350,6 +350,11 @@ const kEventConstructors = {
                                                        },
                                                chromeOnly: true,
                                              },
+  StyleSheetRemovedEvent:                    { create (aName, aProps) {
+                                                         return new StyleSheetRemovedEvent(aName, aProps);
+                                                       },
+                                               chromeOnly: true,
+                                             },
   SubmitEvent:                               { create (aName, aProps) {
                                                          return new SubmitEvent(aName, aProps);
                                                        },

dom/webidl/moz.build

@@ -1108,7 +1108,6 @@ WEBIDL_FILES += [
     "PopStateEvent.webidl",
     "PopupBlockedEvent.webidl",
     "ProgressEvent.webidl",
-    "StyleSheetApplicableStateChangeEvent.webidl",
 ]
 
 # WebExtensions API.
@@ -1188,7 +1187,6 @@ GENERATED_EVENTS_WEBIDL_FILES = [
     "PromiseRejectionEvent.webidl",
     "ScrollViewChangeEvent.webidl",
     "SecurityPolicyViolationEvent.webidl",
-    "StyleSheetApplicableStateChangeEvent.webidl",
     "SubmitEvent.webidl",
     "TaskPriorityChangeEvent.webidl",
     "TCPServerSocketEvent.webidl",

layout/base/tests/browser.ini

@@ -1,8 +1,3 @@
-[browser_bug617076.js]
-[browser_bug839103.js]
-support-files =
-  file_bug839103.html
-  bug839103.css
 [browser_bug1701027-1.js]
 support-files =
   helper_bug1701027-1.html
@@ -13,6 +8,9 @@ support-files =
 run-if = (((os == 'mac') || (os == 'win' && os_version != '6.1' && processor == 'x86_64')) && debug)
 [browser_bug1787079.js]
 run-if = ((os == 'win' && os_version != '6.1' && processor == 'x86_64') && debug)
+[browser_bug1791083.js]
+skip-if = !sessionHistoryInParent
+[browser_bug617076.js]
 [browser_disableDialogs_onbeforeunload.js]
 [browser_onbeforeunload_only_after_interaction.js]
 [browser_onbeforeunload_only_after_interaction_in_frame.js]
@@ -20,10 +18,6 @@ run-if = ((os == 'win' && os_version != '6.1' && processor == 'x86_64') && debug
 support-files =
   test_scroll_into_view_in_oopif.html
   scroll_into_view_in_child.html
-[browser_visual_viewport_iframe.js]
-support-files =
-  test_visual_viewport_in_oopif.html
-  visual_viewport_in_child.html
 [browser_select_popup_position_in_out_of_process_iframe.js]
 skip-if =
   (verify && (os == 'mac')) # bug 1627874
@@ -32,5 +26,11 @@ skip-if =
 support-files =
   !/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js
   !/browser/base/content/test/forms/head.js
-[browser_bug1791083.js]
-skip-if = !sessionHistoryInParent
+[browser_stylesheet_change_events.js]
+support-files =
+  file_stylesheet_change_events.html
+  stylesheet_change_events.css
+[browser_visual_viewport_iframe.js]
+support-files =
+  test_visual_viewport_in_oopif.html
+  visual_viewport_in_child.html

layout/base/tests/browser_bug839103.js

@@ -1,82 +0,0 @@
-const gTestRoot = getRootDirectory(gTestPath).replace(
-  "chrome://mochitests/content/",
-  "http://127.0.0.1:8888/"
-);
-
-add_task(async function test() {
-  await BrowserTestUtils.withNewTab(
-    { gBrowser, url: gTestRoot + "file_bug839103.html" },
-    async function (browser) {
-      await SpecialPowers.spawn(browser, [gTestRoot], testBody);
-    }
-  );
-});
-
-// This function runs entirely in the content process. It doesn't have access
-// any free variables in this file.
-async function testBody(testRoot) {
-  const gStyleSheet = "bug839103.css";
-
-  function unexpectedContentEvent(event) {
-    ok(false, "Received a " + event.type + " event on content");
-  }
-
-  // We've seen the original stylesheet in the document.
-  // Now add a stylesheet on the fly and make sure we see it.
-  let doc = content.document;
-  doc.styleSheetChangeEventsEnabled = true;
-  doc.addEventListener(
-    "StyleSheetApplicableStateChanged",
-    unexpectedContentEvent
-  );
-  doc.defaultView.addEventListener(
-    "StyleSheetApplicableStateChanged",
-    unexpectedContentEvent
-  );
-
-  let link = doc.createElement("link");
-  link.setAttribute("rel", "stylesheet");
-  link.setAttribute("type", "text/css");
-  link.setAttribute("href", testRoot + gStyleSheet);
-
-  let stateChanged = ContentTaskUtils.waitForEvent(
-    docShell.chromeEventHandler,
-    "StyleSheetApplicableStateChanged",
-    true
-  );
-  doc.body.appendChild(link);
-
-  info("waiting for applicable state change event");
-  let evt = await stateChanged;
-  info("received dynamic style sheet applicable state change event");
-  is(
-    evt.type,
-    "StyleSheetApplicableStateChanged",
-    "evt.type has expected value"
-  );
-  is(evt.target, doc, "event targets correct document");
-  is(evt.stylesheet, link.sheet, "evt.stylesheet has the right value");
-  is(evt.applicable, true, "evt.applicable has the right value");
-
-  stateChanged = ContentTaskUtils.waitForEvent(
-    docShell.chromeEventHandler,
-    "StyleSheetApplicableStateChanged",
-    true
-  );
-  link.sheet.disabled = true;
-
-  evt = await stateChanged;
-  is(
-    evt.type,
-    "StyleSheetApplicableStateChanged",
-    "evt.type has expected value"
-  );
-  info(
-    'received dynamic style sheet applicable state change event after media="" changed'
-  );
-  is(evt.target, doc, "event targets correct document");
-  is(evt.stylesheet, link.sheet, "evt.stylesheet has the right value");
-  is(evt.applicable, false, "evt.applicable has the right value");
-
-  doc.body.removeChild(link);
-}

layout/base/tests/browser_stylesheet_change_events.js

@@ -0,0 +1,227 @@
+const gTestRoot = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content/",
+  "http://127.0.0.1:8888/"
+);
+
+add_task(async function test() {
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: gTestRoot + "file_stylesheet_change_events.html" },
+    async function (browser) {
+      await SpecialPowers.spawn(
+        browser,
+        [gTestRoot],
+        testApplicableStateChangeEvent
+      );
+    }
+  );
+});
+
+// This function runs entirely in the content process. It doesn't have access
+// any free variables in this file.
+async function testApplicableStateChangeEvent(testRoot) {
+  // We've seen the original stylesheet in the document.
+  // Now add a stylesheet on the fly and make sure we see it.
+  let doc = content.document;
+  doc.styleSheetChangeEventsEnabled = true;
+
+  const unexpectedContentEvent = event =>
+    ok(false, "Received a " + event.type + " event on content");
+  doc.addEventListener(
+    "StyleSheetApplicableStateChanged",
+    unexpectedContentEvent
+  );
+  doc.defaultView.addEventListener(
+    "StyleSheetApplicableStateChanged",
+    unexpectedContentEvent
+  );
+  doc.addEventListener("StyleSheetRemoved", unexpectedContentEvent);
+  doc.defaultView.addEventListener("StyleSheetRemoved", unexpectedContentEvent);
+
+  function shouldIgnoreEvent(e) {
+    // accessiblecaret.css might be reported, interfering with the test
+    // assertions, so let's ignore it
+    return (
+      e.stylesheet?.href === "resource://content-accessible/accessiblecaret.css"
+    );
+  }
+
+  function waitForStyleApplicableStateChanged() {
+    return ContentTaskUtils.waitForEvent(
+      docShell.chromeEventHandler,
+      "StyleSheetApplicableStateChanged",
+      true,
+      e => !shouldIgnoreEvent(e)
+    );
+  }
+
+  function waitForStyleSheetRemovedEvent() {
+    return ContentTaskUtils.waitForEvent(
+      docShell.chromeEventHandler,
+      "StyleSheetRemoved",
+      true,
+      e => !shouldIgnoreEvent(e)
+    );
+  }
+
+  function checkApplicableStateChangeEvent(event, { applicable, stylesheet }) {
+    is(
+      event.type,
+      "StyleSheetApplicableStateChanged",
+      "event.type has expected value"
+    );
+    is(event.target, doc, "event targets correct document");
+    is(event.stylesheet, stylesheet, "event.stylesheet has the expected value");
+    is(event.applicable, applicable, "event.applicable has the expected value");
+  }
+
+  function checkStyleSheetRemovedEvent(event, { stylesheet }) {
+    is(event.type, "StyleSheetRemoved", "event.type has expected value");
+    is(event.target, doc, "event targets correct document");
+    is(event.stylesheet, stylesheet, "event.stylesheet has the expected value");
+  }
+
+  // Updating the text content will actually create a new StyleSheet instance,
+  // and so we should get one event for the new instance, and another one for
+  // the removal of the "previous"one.
+  function waitForTextContentChange() {
+    return Promise.all([
+      waitForStyleSheetRemovedEvent(),
+      waitForStyleApplicableStateChanged(),
+    ]);
+  }
+
+  let stateChanged, evt;
+
+  {
+    const gStyleSheet = "stylesheet_change_events.css";
+
+    info("Add <link> and wait for applicable state change event");
+    let linkEl = doc.createElement("link");
+    linkEl.setAttribute("rel", "stylesheet");
+    linkEl.setAttribute("type", "text/css");
+    linkEl.setAttribute("href", testRoot + gStyleSheet);
+
+    stateChanged = waitForStyleApplicableStateChanged();
+    doc.body.appendChild(linkEl);
+    evt = await stateChanged;
+
+    ok(true, "received dynamic style sheet applicable state change event");
+    checkApplicableStateChangeEvent(evt, {
+      stylesheet: linkEl.sheet,
+      applicable: true,
+    });
+
+    stateChanged = waitForStyleApplicableStateChanged();
+    linkEl.sheet.disabled = true;
+    evt = await stateChanged;
+
+    ok(true, "received dynamic style sheet applicable state change event");
+    checkApplicableStateChangeEvent(evt, {
+      stylesheet: linkEl.sheet,
+      applicable: false,
+    });
+
+    info("Remove stylesheet and wait for removed event");
+    const removedStylesheet = linkEl.sheet;
+    const onStyleSheetRemoved = waitForStyleSheetRemovedEvent();
+    doc.body.removeChild(linkEl);
+    const removedStyleSheetEvt = await onStyleSheetRemoved;
+
+    ok(true, "received removed sheet event");
+    checkStyleSheetRemovedEvent(removedStyleSheetEvt, {
+      stylesheet: removedStylesheet,
+    });
+  }
+
+  {
+    info("Add <style> node and wait for applicable state changed event");
+    let styleEl = doc.createElement("style");
+    styleEl.textContent = `body { background: tomato; }`;
+
+    stateChanged = waitForStyleApplicableStateChanged();
+    doc.head.appendChild(styleEl);
+    evt = await stateChanged;
+
+    ok(true, "received dynamic style sheet applicable state change event");
+    checkApplicableStateChangeEvent(evt, {
+      stylesheet: styleEl.sheet,
+      applicable: true,
+    });
+
+    info("Updating <style> text content");
+    stateChanged = waitForTextContentChange();
+    const inlineStyleSheetBeforeChange = styleEl.sheet;
+
+    styleEl.textContent = `body { background: gold; }`;
+    const [inlineRemovedEvt, inlineAddedEvt] = await stateChanged;
+
+    ok(true, "received expected style sheet events");
+    checkStyleSheetRemovedEvent(inlineRemovedEvt, {
+      stylesheet: inlineStyleSheetBeforeChange,
+    });
+    checkApplicableStateChangeEvent(inlineAddedEvt, {
+      stylesheet: styleEl.sheet,
+      applicable: true,
+    });
+
+    info("Remove stylesheet and wait for removed event");
+    const onStyleSheetRemoved = waitForStyleSheetRemovedEvent();
+
+    const removedInlineStylesheet = styleEl.sheet;
+    styleEl.remove();
+    const removedStyleSheetEvt = await onStyleSheetRemoved;
+
+    ok(true, "received removed style sheet event");
+    checkStyleSheetRemovedEvent(removedStyleSheetEvt, {
+      stylesheet: removedInlineStylesheet,
+    });
+  }
+
+  {
+    info(
+      "Create a custom element and check we get an event for its stylesheet"
+    );
+    stateChanged = waitForStyleApplicableStateChanged();
+    const el = doc.createElement("div");
+    const shadowRoot = el.attachShadow({ mode: "open" });
+    doc.body.appendChild(el);
+    shadowRoot.innerHTML = `
+        <span>custom</span>
+        <style>
+          span { color: salmon; }
+        </style>`;
+    evt = await stateChanged;
+
+    ok(true, "received dynamic style sheet applicable state change event");
+    const shadowStyleEl = shadowRoot.querySelector("style");
+    checkApplicableStateChangeEvent(evt, {
+      stylesheet: shadowStyleEl.sheet,
+      applicable: true,
+    });
+
+    info("Updating <style> text content");
+    stateChanged = waitForTextContentChange();
+    const styleSheetBeforeChange = shadowStyleEl.sheet;
+    shadowStyleEl.textContent = `span { color: cyan; }`;
+    const [removedEvt, addedEvt] = await stateChanged;
+
+    ok(true, "received expected style sheet events");
+    checkStyleSheetRemovedEvent(removedEvt, {
+      stylesheet: styleSheetBeforeChange,
+    });
+    checkApplicableStateChangeEvent(addedEvt, {
+      stylesheet: shadowStyleEl.sheet,
+      applicable: true,
+    });
+
+    info("Remove stylesheet and wait for removed event");
+    const onStyleSheetRemoved = waitForStyleSheetRemovedEvent();
+    const removedShadowStylesheet = shadowStyleEl.sheet;
+    shadowStyleEl.remove();
+    const removedStyleSheetEvt = await onStyleSheetRemoved;
+    ok(true, "received removed style sheet event");
+    checkStyleSheetRemovedEvent(removedStyleSheetEvt, {
+      stylesheet: removedShadowStylesheet,
+    });
+  }
+}

tools/lint/eslint/eslint-plugin-mozilla/lib/environments/privileged.js

@@ -648,6 +648,7 @@ module.exports = {
     StyleSheet: false,
     StyleSheetApplicableStateChangeEvent: false,
     StyleSheetList: false,
+    StyleSheetRemovedEvent: false,
     SubtleCrypto: false,
     SyncMessageSender: false,
     TCPServerSocket: false,