accessible/base/nsCoreUtils.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "nsCoreUtils.h"
   7
   8 #include "nsIAccessibleTypes.h"
   9
  10 #include "nsIBaseWindow.h"
  11 #include "nsIDocShellTreeOwner.h"
  12 #include "mozilla/dom/Document.h"
  13 #include "nsRange.h"
  14 #include "nsXULElement.h"
  15 #include "nsIDocShell.h"
  16 #include "nsIObserverService.h"
  17 #include "nsPresContext.h"
  18 #include "nsIScrollableFrame.h"
  19 #include "nsISelectionController.h"
  20 #include "nsISimpleEnumerator.h"
  21 #include "mozilla/dom/TouchEvent.h"
  22 #include "mozilla/ErrorResult.h"
  23 #include "mozilla/EventListenerManager.h"
  24 #include "mozilla/EventStateManager.h"
  25 #include "mozilla/MouseEvents.h"
  26 #include "mozilla/PresShell.h"
  27 #include "mozilla/TouchEvents.h"
  28 #include "nsView.h"
  29 #include "nsGkAtoms.h"
  30
  31 #include "nsComponentManagerUtils.h"
  32
  33 #include "XULTreeElement.h"
  34 #include "nsIContentInlines.h"
  35 #include "nsTreeColumns.h"
  36 #include "mozilla/dom/DocumentInlines.h"
  37 #include "mozilla/dom/Element.h"
  38 #include "mozilla/dom/HTMLLabelElement.h"
  39 #include "mozilla/dom/MouseEventBinding.h"
  40 #include "mozilla/dom/Selection.h"
  41
  42 using namespace mozilla;
  43
  44 using mozilla::dom::DOMRect;
  45 using mozilla::dom::Element;
  46 using mozilla::dom::Selection;
  47 using mozilla::dom::XULTreeElement;
  48
  49 ////////////////////////////////////////////////////////////////////////////////
  50 // nsCoreUtils
  51 ////////////////////////////////////////////////////////////////////////////////
  52
  53 bool nsCoreUtils::IsLabelWithControl(nsIContent* aContent) {
  54   dom::HTMLLabelElement* label = dom::HTMLLabelElement::FromNode(aContent);
  55   if (label && label->GetControl()) return true;
  56
  57   return false;
  58 }
  59
  60 bool nsCoreUtils::HasClickListener(nsIContent* aContent) {
  61   NS_ENSURE_TRUE(aContent, false);
  62   EventListenerManager* listenerManager =
  63       aContent->GetExistingListenerManager();
  64
  65   return listenerManager &&
  66          (listenerManager->HasListenersFor(nsGkAtoms::onclick) ||
  67           listenerManager->HasListenersFor(nsGkAtoms::onmousedown) ||
  68           listenerManager->HasListenersFor(nsGkAtoms::onmouseup));
  69 }
  70
  71 void nsCoreUtils::DispatchClickEvent(XULTreeElement* aTree, int32_t aRowIndex,
  72                                      nsTreeColumn* aColumn,
  73                                      const nsAString& aPseudoElt) {
  74   RefPtr<dom::Element> tcElm = aTree->GetTreeBody();
  75   if (!tcElm) return;
  76
  77   Document* document = tcElm->GetUncomposedDoc();
  78   if (!document) return;
  79
  80   RefPtr<PresShell> presShell = document->GetPresShell();
  81   if (!presShell) {
  82     return;
  83   }
  84
  85   // Ensure row is visible.
  86   aTree->EnsureRowIsVisible(aRowIndex);
  87
  88   // Calculate x and y coordinates.
  89   nsresult rv;
  90   nsIntRect rect =
  91       aTree->GetCoordsForCellItem(aRowIndex, aColumn, aPseudoElt, rv);
  92   if (NS_FAILED(rv)) {
  93     return;
  94   }
  95
  96   RefPtr<DOMRect> treeBodyRect = tcElm->GetBoundingClientRect();
  97   int32_t tcX = (int32_t)treeBodyRect->X();
  98   int32_t tcY = (int32_t)treeBodyRect->Y();
  99
 100   // Dispatch mouse events.
 101   AutoWeakFrame tcFrame = tcElm->GetPrimaryFrame();
 102   nsIFrame* rootFrame = presShell->GetRootFrame();
 103
 104   nsPoint offset;
 105   nsCOMPtr<nsIWidget> rootWidget =
 106       rootFrame->GetView()->GetNearestWidget(&offset);
 107
 108   RefPtr<nsPresContext> presContext = presShell->GetPresContext();
 109
 110   int32_t cnvdX = presContext->CSSPixelsToDevPixels(tcX + int32_t(rect.x) + 1) +
 111                   presContext->AppUnitsToDevPixels(offset.x);
 112   int32_t cnvdY = presContext->CSSPixelsToDevPixels(tcY + int32_t(rect.y) + 1) +
 113                   presContext->AppUnitsToDevPixels(offset.y);
 114
 115   // XUL is just desktop, so there is no real reason for senfing touch events.
 116   DispatchMouseEvent(eMouseDown, cnvdX, cnvdY, tcElm, tcFrame, presShell,
 117                      rootWidget);
 118
 119   DispatchMouseEvent(eMouseUp, cnvdX, cnvdY, tcElm, tcFrame, presShell,
 120                      rootWidget);
 121 }
 122
 123 void nsCoreUtils::DispatchMouseEvent(EventMessage aMessage, int32_t aX,
 124                                      int32_t aY, nsIContent* aContent,
 125                                      nsIFrame* aFrame, PresShell* aPresShell,
 126                                      nsIWidget* aRootWidget) {
 127   WidgetMouseEvent event(true, aMessage, aRootWidget, WidgetMouseEvent::eReal,
 128                          WidgetMouseEvent::eNormal);
 129
 130   event.mRefPoint = LayoutDeviceIntPoint(aX, aY);
 131
 132   event.mClickCount = 1;
 133   event.mButton = MouseButton::ePrimary;
 134   event.mTime = PR_IntervalNow();
 135   event.mInputSource = dom::MouseEvent_Binding::MOZ_SOURCE_UNKNOWN;
 136
 137   nsEventStatus status = nsEventStatus_eIgnore;
 138   aPresShell->HandleEventWithTarget(&event, aFrame, aContent, &status);
 139 }
 140
 141 void nsCoreUtils::DispatchTouchEvent(EventMessage aMessage, int32_t aX,
 142                                      int32_t aY, nsIContent* aContent,
 143                                      nsIFrame* aFrame, PresShell* aPresShell,
 144                                      nsIWidget* aRootWidget) {
 145   nsIDocShell* docShell = nullptr;
 146   if (aPresShell->GetDocument()) {
 147     docShell = aPresShell->GetDocument()->GetDocShell();
 148   }
 149   if (!dom::TouchEvent::PrefEnabled(docShell)) {
 150     return;
 151   }
 152
 153   WidgetTouchEvent event(true, aMessage, aRootWidget);
 154
 155   event.mTime = PR_IntervalNow();
 156
 157   // XXX: Touch has an identifier of -1 to hint that it is synthesized.
 158   RefPtr<dom::Touch> t = new dom::Touch(-1, LayoutDeviceIntPoint(aX, aY),
 159                                         LayoutDeviceIntPoint(1, 1), 0.0f, 1.0f);
 160   t->SetTouchTarget(aContent);
 161   event.mTouches.AppendElement(t);
 162   nsEventStatus status = nsEventStatus_eIgnore;
 163   aPresShell->HandleEventWithTarget(&event, aFrame, aContent, &status);
 164 }
 165
 166 uint32_t nsCoreUtils::GetAccessKeyFor(nsIContent* aContent) {
 167   // Accesskeys are registered by @accesskey attribute only. At first check
 168   // whether it is presented on the given element to avoid the slow
 169   // EventStateManager::GetRegisteredAccessKey() method.
 170   if (!aContent->IsElement() || !aContent->AsElement()->HasAttr(
 171                                     kNameSpaceID_None, nsGkAtoms::accesskey)) {
 172     return 0;
 173   }
 174
 175   nsPresContext* presContext = aContent->OwnerDoc()->GetPresContext();
 176   if (!presContext) return 0;
 177
 178   EventStateManager* esm = presContext->EventStateManager();
 179   if (!esm) return 0;
 180
 181   return esm->GetRegisteredAccessKey(aContent->AsElement());
 182 }
 183
 184 nsIContent* nsCoreUtils::GetDOMElementFor(nsIContent* aContent) {
 185   if (aContent->IsElement()) return aContent;
 186
 187   if (aContent->IsText()) return aContent->GetFlattenedTreeParent();
 188
 189   return nullptr;
 190 }
 191
 192 nsINode* nsCoreUtils::GetDOMNodeFromDOMPoint(nsINode* aNode, uint32_t aOffset) {
 193   if (aNode && aNode->IsElement()) {
 194     uint32_t childCount = aNode->GetChildCount();
 195     NS_ASSERTION(aOffset <= childCount, "Wrong offset of the DOM point!");
 196
 197     // The offset can be after last child of container node that means DOM point
 198     // is placed immediately after the last child. In this case use the DOM node
 199     // from the given DOM point is used as result node.
 200     if (aOffset != childCount) return aNode->GetChildAt_Deprecated(aOffset);
 201   }
 202
 203   return aNode;
 204 }
 205
 206 bool nsCoreUtils::IsAncestorOf(nsINode* aPossibleAncestorNode,
 207                                nsINode* aPossibleDescendantNode,
 208                                nsINode* aRootNode) {
 209   NS_ENSURE_TRUE(aPossibleAncestorNode && aPossibleDescendantNode, false);
 210
 211   nsINode* parentNode = aPossibleDescendantNode;
 212   while ((parentNode = parentNode->GetParentNode()) &&
 213          parentNode != aRootNode) {
 214     if (parentNode == aPossibleAncestorNode) return true;
 215   }
 216
 217   return false;
 218 }
 219
 220 nsresult nsCoreUtils::ScrollSubstringTo(nsIFrame* aFrame, nsRange* aRange,
 221                                         uint32_t aScrollType) {
 222   ScrollAxis vertical, horizontal;
 223   ConvertScrollTypeToPercents(aScrollType, &vertical, &horizontal);
 224
 225   return ScrollSubstringTo(aFrame, aRange, vertical, horizontal);
 226 }
 227
 228 nsresult nsCoreUtils::ScrollSubstringTo(nsIFrame* aFrame, nsRange* aRange,
 229                                         ScrollAxis aVertical,
 230                                         ScrollAxis aHorizontal) {
 231   if (!aFrame || !aRange) {
 232     return NS_ERROR_FAILURE;
 233   }
 234
 235   nsPresContext* presContext = aFrame->PresContext();
 236
 237   nsCOMPtr<nsISelectionController> selCon;
 238   aFrame->GetSelectionController(presContext, getter_AddRefs(selCon));
 239   NS_ENSURE_TRUE(selCon, NS_ERROR_FAILURE);
 240
 241   RefPtr<dom::Selection> selection =
 242       selCon->GetSelection(nsISelectionController::SELECTION_ACCESSIBILITY);
 243
 244   selection->RemoveAllRanges(IgnoreErrors());
 245   selection->AddRangeAndSelectFramesAndNotifyListeners(*aRange, IgnoreErrors());
 246
 247   selection->ScrollIntoView(nsISelectionController::SELECTION_ANCHOR_REGION,
 248                             aVertical, aHorizontal,
 249                             Selection::SCROLL_SYNCHRONOUS);
 250
 251   selection->CollapseToStart(IgnoreErrors());
 252
 253   return NS_OK;
 254 }
 255
 256 void nsCoreUtils::ScrollFrameToPoint(nsIFrame* aScrollableFrame,
 257                                      nsIFrame* aFrame,
 258                                      const LayoutDeviceIntPoint& aPoint) {
 259   nsIScrollableFrame* scrollableFrame = do_QueryFrame(aScrollableFrame);
 260   if (!scrollableFrame) return;
 261
 262   nsPoint point = LayoutDeviceIntPoint::ToAppUnits(
 263       aPoint, aFrame->PresContext()->AppUnitsPerDevPixel());
 264   nsRect frameRect = aFrame->GetScreenRectInAppUnits();
 265   nsPoint deltaPoint = point - frameRect.TopLeft();
 266
 267   nsPoint scrollPoint = scrollableFrame->GetScrollPosition();
 268   scrollPoint -= deltaPoint;
 269
 270   scrollableFrame->ScrollTo(scrollPoint, ScrollMode::Instant);
 271 }
 272
 273 void nsCoreUtils::ConvertScrollTypeToPercents(uint32_t aScrollType,
 274                                               ScrollAxis* aVertical,
 275                                               ScrollAxis* aHorizontal) {
 276   WhereToScroll whereY, whereX;
 277   WhenToScroll whenY, whenX;
 278   switch (aScrollType) {
 279     case nsIAccessibleScrollType::SCROLL_TYPE_TOP_LEFT:
 280       whereY = kScrollToTop;
 281       whenY = WhenToScroll::Always;
 282       whereX = kScrollToLeft;
 283       whenX = WhenToScroll::Always;
 284       break;
 285     case nsIAccessibleScrollType::SCROLL_TYPE_BOTTOM_RIGHT:
 286       whereY = kScrollToBottom;
 287       whenY = WhenToScroll::Always;
 288       whereX = kScrollToRight;
 289       whenX = WhenToScroll::Always;
 290       break;
 291     case nsIAccessibleScrollType::SCROLL_TYPE_TOP_EDGE:
 292       whereY = kScrollToTop;
 293       whenY = WhenToScroll::Always;
 294       whereX = kScrollMinimum;
 295       whenX = WhenToScroll::IfNotFullyVisible;
 296       break;
 297     case nsIAccessibleScrollType::SCROLL_TYPE_BOTTOM_EDGE:
 298       whereY = kScrollToBottom;
 299       whenY = WhenToScroll::Always;
 300       whereX = kScrollMinimum;
 301       whenX = WhenToScroll::IfNotFullyVisible;
 302       break;
 303     case nsIAccessibleScrollType::SCROLL_TYPE_LEFT_EDGE:
 304       whereY = kScrollMinimum;
 305       whenY = WhenToScroll::IfNotFullyVisible;
 306       whereX = kScrollToLeft;
 307       whenX = WhenToScroll::Always;
 308       break;
 309     case nsIAccessibleScrollType::SCROLL_TYPE_RIGHT_EDGE:
 310       whereY = kScrollMinimum;
 311       whenY = WhenToScroll::IfNotFullyVisible;
 312       whereX = kScrollToRight;
 313       whenX = WhenToScroll::Always;
 314       break;
 315     default:
 316       whereY = kScrollMinimum;
 317       whenY = WhenToScroll::IfNotFullyVisible;
 318       whereX = kScrollMinimum;
 319       whenX = WhenToScroll::IfNotFullyVisible;
 320   }
 321   *aVertical = ScrollAxis(whereY, whenY);
 322   *aHorizontal = ScrollAxis(whereX, whenX);
 323 }
 324
 325 LayoutDeviceIntPoint nsCoreUtils::GetScreenCoordsForWindow(nsINode* aNode) {
 326   LayoutDeviceIntPoint coords(0, 0);
 327   nsCOMPtr<nsIDocShellTreeItem> treeItem(GetDocShellFor(aNode));
 328   if (!treeItem) return coords;
 329
 330   nsCOMPtr<nsIDocShellTreeOwner> treeOwner;
 331   treeItem->GetTreeOwner(getter_AddRefs(treeOwner));
 332   if (!treeOwner) return coords;
 333
 334   nsCOMPtr<nsIBaseWindow> baseWindow = do_QueryInterface(treeOwner);
 335   if (baseWindow) {
 336     baseWindow->GetPosition(&coords.x, &coords.y);  // in device pixels
 337   }
 338
 339   return coords;
 340 }
 341
 342 already_AddRefed<nsIDocShell> nsCoreUtils::GetDocShellFor(nsINode* aNode) {
 343   if (!aNode) return nullptr;
 344
 345   nsCOMPtr<nsIDocShell> docShell = aNode->OwnerDoc()->GetDocShell();
 346   return docShell.forget();
 347 }
 348
 349 bool nsCoreUtils::IsRootDocument(Document* aDocument) {
 350   nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = aDocument->GetDocShell();
 351   NS_ASSERTION(docShellTreeItem, "No document shell for document!");
 352
 353   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
 354   docShellTreeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
 355
 356   return !parentTreeItem;
 357 }
 358
 359 bool nsCoreUtils::IsTopLevelContentDocInProcess(Document* aDocumentNode) {
 360   mozilla::dom::BrowsingContext* bc = aDocumentNode->GetBrowsingContext();
 361   return bc->IsContent() && (
 362                                 // Tab document.
 363                                 bc->IsTop() ||
 364                                 // Out-of-process iframe.
 365                                 !bc->GetParent()->IsInProcess());
 366 }
 367
 368 bool nsCoreUtils::IsErrorPage(Document* aDocument) {
 369   nsIURI* uri = aDocument->GetDocumentURI();
 370   if (!uri->SchemeIs("about")) {
 371     return false;
 372   }
 373
 374   nsAutoCString path;
 375   uri->GetPathQueryRef(path);
 376
 377   constexpr auto neterror = "neterror"_ns;
 378   constexpr auto certerror = "certerror"_ns;
 379
 380   return StringBeginsWith(path, neterror) || StringBeginsWith(path, certerror);
 381 }
 382
 383 PresShell* nsCoreUtils::GetPresShellFor(nsINode* aNode) {
 384   return aNode->OwnerDoc()->GetPresShell();
 385 }
 386
 387 bool nsCoreUtils::GetID(nsIContent* aContent, nsAString& aID) {
 388   return aContent->IsElement() &&
 389          aContent->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::id, aID);
 390 }
 391
 392 bool nsCoreUtils::GetUIntAttr(nsIContent* aContent, nsAtom* aAttr,
 393                               int32_t* aUInt) {
 394   nsAutoString value;
 395   if (!aContent->IsElement()) {
 396     return false;
 397   }
 398   aContent->AsElement()->GetAttr(kNameSpaceID_None, aAttr, value);
 399   if (!value.IsEmpty()) {
 400     nsresult error = NS_OK;
 401     int32_t integer = value.ToInteger(&error);
 402     if (NS_SUCCEEDED(error) && integer > 0) {
 403       *aUInt = integer;
 404       return true;
 405     }
 406   }
 407
 408   return false;
 409 }
 410
 411 void nsCoreUtils::GetLanguageFor(nsIContent* aContent, nsIContent* aRootContent,
 412                                  nsAString& aLanguage) {
 413   aLanguage.Truncate();
 414
 415   nsIContent* walkUp = aContent;
 416   while (walkUp && walkUp != aRootContent &&
 417          (!walkUp->IsElement() ||
 418           !walkUp->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::lang,
 419                                         aLanguage))) {
 420     walkUp = walkUp->GetParent();
 421   }
 422 }
 423
 424 XULTreeElement* nsCoreUtils::GetTree(nsIContent* aContent) {
 425   // Find DOMNode's parents recursively until reach the <tree> tag
 426   nsIContent* currentContent = aContent;
 427   while (currentContent) {
 428     if (currentContent->NodeInfo()->Equals(nsGkAtoms::tree, kNameSpaceID_XUL)) {
 429       return XULTreeElement::FromNode(currentContent);
 430     }
 431     currentContent = currentContent->GetFlattenedTreeParent();
 432   }
 433
 434   return nullptr;
 435 }
 436
 437 already_AddRefed<nsTreeColumn> nsCoreUtils::GetFirstSensibleColumn(
 438     XULTreeElement* aTree, FlushType aFlushType) {
 439   if (!aTree) {
 440     return nullptr;
 441   }
 442
 443   RefPtr<nsTreeColumns> cols = aTree->GetColumns(aFlushType);
 444   if (!cols) {
 445     return nullptr;
 446   }
 447
 448   RefPtr<nsTreeColumn> column = cols->GetFirstColumn();
 449   if (column && IsColumnHidden(column)) return GetNextSensibleColumn(column);
 450
 451   return column.forget();
 452 }
 453
 454 uint32_t nsCoreUtils::GetSensibleColumnCount(XULTreeElement* aTree) {
 455   uint32_t count = 0;
 456   if (!aTree) {
 457     return count;
 458   }
 459
 460   RefPtr<nsTreeColumns> cols = aTree->GetColumns();
 461   if (!cols) {
 462     return count;
 463   }
 464
 465   nsTreeColumn* column = cols->GetFirstColumn();
 466
 467   while (column) {
 468     if (!IsColumnHidden(column)) count++;
 469
 470     column = column->GetNext();
 471   }
 472
 473   return count;
 474 }
 475
 476 already_AddRefed<nsTreeColumn> nsCoreUtils::GetSensibleColumnAt(
 477     XULTreeElement* aTree, uint32_t aIndex) {
 478   if (!aTree) {
 479     return nullptr;
 480   }
 481
 482   uint32_t idx = aIndex;
 483
 484   nsCOMPtr<nsTreeColumn> column = GetFirstSensibleColumn(aTree);
 485   while (column) {
 486     if (idx == 0) return column.forget();
 487
 488     idx--;
 489     column = GetNextSensibleColumn(column);
 490   }
 491
 492   return nullptr;
 493 }
 494
 495 already_AddRefed<nsTreeColumn> nsCoreUtils::GetNextSensibleColumn(
 496     nsTreeColumn* aColumn) {
 497   if (!aColumn) {
 498     return nullptr;
 499   }
 500
 501   RefPtr<nsTreeColumn> nextColumn = aColumn->GetNext();
 502
 503   while (nextColumn && IsColumnHidden(nextColumn)) {
 504     nextColumn = nextColumn->GetNext();
 505   }
 506
 507   return nextColumn.forget();
 508 }
 509
 510 already_AddRefed<nsTreeColumn> nsCoreUtils::GetPreviousSensibleColumn(
 511     nsTreeColumn* aColumn) {
 512   if (!aColumn) {
 513     return nullptr;
 514   }
 515
 516   RefPtr<nsTreeColumn> prevColumn = aColumn->GetPrevious();
 517
 518   while (prevColumn && IsColumnHidden(prevColumn)) {
 519     prevColumn = prevColumn->GetPrevious();
 520   }
 521
 522   return prevColumn.forget();
 523 }
 524
 525 bool nsCoreUtils::IsColumnHidden(nsTreeColumn* aColumn) {
 526   if (!aColumn) {
 527     return false;
 528   }
 529
 530   Element* element = aColumn->Element();
 531   return element->AttrValueIs(kNameSpaceID_None, nsGkAtoms::hidden,
 532                               nsGkAtoms::_true, eCaseMatters);
 533 }
 534
 535 void nsCoreUtils::ScrollTo(PresShell* aPresShell, nsIContent* aContent,
 536                            uint32_t aScrollType) {
 537   ScrollAxis vertical, horizontal;
 538   ConvertScrollTypeToPercents(aScrollType, &vertical, &horizontal);
 539   aPresShell->ScrollContentIntoView(aContent, vertical, horizontal,
 540                                     ScrollFlags::ScrollOverflowHidden);
 541 }
 542
 543 bool nsCoreUtils::IsHTMLTableHeader(nsIContent* aContent) {
 544   return aContent->NodeInfo()->Equals(nsGkAtoms::th) ||
 545          (aContent->IsElement() &&
 546           aContent->AsElement()->HasAttr(kNameSpaceID_None, nsGkAtoms::scope));
 547 }
 548
 549 bool nsCoreUtils::IsWhitespaceString(const nsAString& aString) {
 550   nsAString::const_char_iterator iterBegin, iterEnd;
 551
 552   aString.BeginReading(iterBegin);
 553   aString.EndReading(iterEnd);
 554
 555   while (iterBegin != iterEnd && IsWhitespace(*iterBegin)) ++iterBegin;
 556
 557   return iterBegin == iterEnd;
 558 }
 559
 560 bool nsCoreUtils::AccEventObserversExist() {
 561   nsCOMPtr<nsIObserverService> obsService = services::GetObserverService();
 562   NS_ENSURE_TRUE(obsService, false);
 563
 564   nsCOMPtr<nsISimpleEnumerator> observers;
 565   obsService->EnumerateObservers(NS_ACCESSIBLE_EVENT_TOPIC,
 566                                  getter_AddRefs(observers));
 567   NS_ENSURE_TRUE(observers, false);
 568
 569   bool hasObservers = false;
 570   observers->HasMoreElements(&hasObservers);
 571
 572   return hasObservers;
 573 }
 574
 575 void nsCoreUtils::DispatchAccEvent(RefPtr<nsIAccessibleEvent> event) {
 576   nsCOMPtr<nsIObserverService> obsService = services::GetObserverService();
 577   NS_ENSURE_TRUE_VOID(obsService);
 578
 579   obsService->NotifyObservers(event, NS_ACCESSIBLE_EVENT_TOPIC, nullptr);
 580 }
 581
 582 bool nsCoreUtils::IsDisplayContents(nsIContent* aContent) {
 583   auto* element = Element::FromNodeOrNull(aContent);
 584   return element && element->IsDisplayContents();
 585 }
 586
 587 bool nsCoreUtils::CanCreateAccessibleWithoutFrame(nsIContent* aContent) {
 588   auto* element = Element::FromNodeOrNull(aContent);
 589   if (!element) {
 590     return false;
 591   }
 592   if (!element->HasServoData() || Servo_Element_IsDisplayNone(element)) {
 593     // Out of the flat tree or in a display: none subtree.
 594     return false;
 595   }
 596   if (element->IsDisplayContents()) {
 597     return true;
 598   }
 599   // We don't have a frame, but we're not display: contents either.
 600   // For now, only create accessibles for <option>/<optgroup> as our combobox
 601   // select code depends on it.
 602   return element->IsAnyOfHTMLElements(nsGkAtoms::option, nsGkAtoms::optgroup);
 603 }
 604
 605 bool nsCoreUtils::IsDocumentVisibleConsideringInProcessAncestors(
 606     const Document* aDocument) {
 607   const Document* parent = aDocument;
 608   do {
 609     if (!parent->IsVisible()) {
 610       return false;
 611     }
 612   } while ((parent = parent->GetInProcessParentDocument()));
 613   return true;
 614 }