Bug 1611060 - Dispatch a11y scroll events for all DOM scrolls. r=Jamie

Currently, only documents dispatch scroll events when in reality any
element can have scrollable overflows.

Differential Revision: https://phabricator.services.mozilla.com/D62665

--HG--
extra : moz-landing-system : lando

accessible/base/NotificationController.cpp

@@ -638,10 +638,6 @@ void NotificationController::WillRefresh(mozilla::TimeStamp aTime) {
                  "isn't created!");
   }
 
-  // Initialize scroll support if needed.
-  if (!(mDocument->mDocFlags & DocAccessible::eScrollInitialized))
-    mDocument->AddScrollListener();
-
   // Process rendered text change notifications.
   for (auto iter = mTextHash.Iter(); !iter.Done(); iter.Next()) {
     nsCOMPtrHashKey<nsIContent>* entry = iter.Get();

accessible/generic/DocAccessible-inl.h

@@ -77,27 +77,6 @@ inline void DocAccessible::UpdateText(nsIContent* aTextNode) {
     mNotificationController->ScheduleTextUpdate(aTextNode);
 }
 
-inline void DocAccessible::AddScrollListener() {
-  // Delay scroll initializing until the document has a root frame.
-  if (!mPresShell->GetRootFrame()) return;
-
-  mDocFlags |= eScrollInitialized;
-  nsIScrollableFrame* sf = mPresShell->GetRootScrollFrameAsScrollable();
-  if (sf) {
-    sf->AddScrollPositionListener(this);
-
-#ifdef A11Y_LOG
-    if (logging::IsEnabled(logging::eDocCreate))
-      logging::Text("add scroll listener");
-#endif
-  }
-}
-
-inline void DocAccessible::RemoveScrollListener() {
-  nsIScrollableFrame* sf = mPresShell->GetRootScrollFrameAsScrollable();
-  if (sf) sf->RemoveScrollPositionListener(this);
-}
-
 inline void DocAccessible::NotifyOfLoad(uint32_t aLoadEventType) {
   mLoadState |= eDOMLoaded;
   mLoadEventType = aLoadEventType;

accessible/generic/DocAccessible.cpp

@@ -81,7 +81,6 @@ DocAccessible::DocAccessible(dom::Document* aDocument,
       mAccessibleCache(kDefaultCacheLength),
       mNodeToAccessibleMap(kDefaultCacheLength),
       mDocumentNode(aDocument),
-      mScrollPositionChangedTicks(0),
       mLoadState(eTreeConstructionPending),
       mDocFlags(0),
       mLoadEventType(0),
@@ -510,9 +509,6 @@ nsresult DocAccessible::AddEventListeners() {
 // DocAccessible protected member
 nsresult DocAccessible::RemoveEventListeners() {
   // Remove listeners associated with content documents
-  // Remove scroll position listener
-  RemoveScrollListener();
-
   NS_ASSERTION(mDocumentNode, "No document during removal of listeners.");
 
   if (mDocumentNode) {
@@ -545,7 +541,14 @@ void DocAccessible::ScrollTimerCallback(nsITimer* aTimer, void* aClosure) {
   DocAccessible* docAcc = reinterpret_cast<DocAccessible*>(aClosure);
 
   if (docAcc) {
-    docAcc->DispatchScrollingEvent(nsIAccessibleEvent::EVENT_SCROLLING_END);
+    // Dispatch a scroll-end for all entries in table. They have not
+    // been scrolled in at least `kScrollEventInterval`.
+    for (auto iter = docAcc->mLastScrollingDispatch.Iter(); !iter.Done();
+         iter.Next()) {
+      docAcc->DispatchScrollingEvent(iter.Key(),
+                                     nsIAccessibleEvent::EVENT_SCROLLING_END);
+      iter.Remove();
+    }
 
     if (docAcc->mScrollWatchTimer) {
       docAcc->mScrollWatchTimer = nullptr;
@@ -554,17 +557,16 @@ void DocAccessible::ScrollTimerCallback(nsITimer* aTimer, void* aClosure) {
   }
 }
 
-////////////////////////////////////////////////////////////////////////////////
-// nsIScrollPositionListener
-
-void DocAccessible::ScrollPositionDidChange(nscoord aX, nscoord aY) {
+void DocAccessible::HandleScroll(nsINode* aTarget) {
   const uint32_t kScrollEventInterval = 100;
-  TimeStamp timestamp = TimeStamp::Now();
-  if (mLastScrollingDispatch.IsNull() ||
-      (timestamp - mLastScrollingDispatch).ToMilliseconds() >=
-          kScrollEventInterval) {
-    DispatchScrollingEvent(nsIAccessibleEvent::EVENT_SCROLLING);
-    mLastScrollingDispatch = timestamp;
+  TimeStamp now = TimeStamp::Now();
+  TimeStamp lastDispatch;
+  // If we haven't dispatched a scrolling event for a target in at least
+  // kScrollEventInterval milliseconds, dispatch one now.
+  if (!mLastScrollingDispatch.Get(aTarget, &lastDispatch) ||
+      (now - lastDispatch).ToMilliseconds() >= kScrollEventInterval) {
+    DispatchScrollingEvent(aTarget, nsIAccessibleEvent::EVENT_SCROLLING);
+    mLastScrollingDispatch.Put(aTarget, now);
   }
 
   // If timer callback is still pending, push it 100ms into the future.
@@ -2522,27 +2524,38 @@ void DocAccessible::SetIPCDoc(DocAccessibleChild* aIPCDoc) {
   mIPCDoc = aIPCDoc;
 }
 
-void DocAccessible::DispatchScrollingEvent(uint32_t aEventType) {
-  nsIScrollableFrame* sf = mPresShell->GetRootScrollFrameAsScrollable();
-  if (!sf) {
+void DocAccessible::DispatchScrollingEvent(nsINode* aTarget,
+                                           uint32_t aEventType) {
+  Accessible* acc = GetAccessible(aTarget);
+  if (!acc) {
     return;
   }
 
-  int32_t appUnitsPerDevPixel =
-      mPresShell->GetPresContext()->AppUnitsPerDevPixel();
-  LayoutDevicePoint scrollPoint =
-      LayoutDevicePoint::FromAppUnits(sf->GetScrollPosition(),
-                                      appUnitsPerDevPixel) *
-      mPresShell->GetResolution();
+  LayoutDevicePoint scrollPoint;
+  LayoutDeviceRect scrollRange;
+  nsIScrollableFrame* sf = acc == this
+                               ? mPresShell->GetRootScrollFrameAsScrollable()
+                               : acc->GetFrame()->GetScrollTargetFrame();
 
-  LayoutDeviceRect scrollRange =
-      LayoutDeviceRect::FromAppUnits(sf->GetScrollRange(), appUnitsPerDevPixel);
-  scrollRange.ScaleRoundOut(mPresShell->GetResolution());
+  // If there is no scrollable frame, it's likely a scroll in a popup, like
+  // <select>. Just send an event with no scroll info. The scroll info
+  // is currently only used on Android, and popups are rendered natively
+  // there.
+  if (sf) {
+    int32_t appUnitsPerDevPixel =
+        mPresShell->GetPresContext()->AppUnitsPerDevPixel();
+    scrollPoint = LayoutDevicePoint::FromAppUnits(sf->GetScrollPosition(),
+                                                  appUnitsPerDevPixel) *
+                  mPresShell->GetResolution();
+
+    scrollRange = LayoutDeviceRect::FromAppUnits(sf->GetScrollRange(),
+                                                 appUnitsPerDevPixel);
+    scrollRange.ScaleRoundOut(mPresShell->GetResolution());
+  }
 
   RefPtr<AccEvent> event =
-      new AccScrollingEvent(aEventType, this, scrollPoint.x, scrollPoint.y,
+      new AccScrollingEvent(aEventType, acc, scrollPoint.x, scrollPoint.y,
                             scrollRange.width, scrollRange.height);
-
   nsEventShell::FireEvent(event);
 }
 

accessible/generic/DocAccessible.h

@@ -17,7 +17,6 @@
 #include "mozilla/dom/Document.h"
 #include "nsIDocumentObserver.h"
 #include "nsIObserver.h"
-#include "nsIScrollPositionListener.h"
 #include "nsITimer.h"
 
 class nsAccessiblePivot;
@@ -45,7 +44,6 @@ class TNotification;
 class DocAccessible : public HyperTextAccessibleWrap,
                       public nsIDocumentObserver,
                       public nsIObserver,
-                      public nsIScrollPositionListener,
                       public nsSupportsWeakReference,
                       public nsIAccessiblePivotObserver {
   NS_DECL_ISUPPORTS_INHERITED
@@ -60,10 +58,6 @@ class DocAccessible : public HyperTextAccessibleWrap,
  public:
   DocAccessible(Document* aDocument, PresShell* aPresShell);
 
-  // nsIScrollPositionListener
-  virtual void ScrollPositionWillChange(nscoord aX, nscoord aY) override {}
-  virtual void ScrollPositionDidChange(nscoord aX, nscoord aY) override;
-
   // nsIDocumentObserver
   NS_DECL_NSIDOCUMENTOBSERVER
 
@@ -384,6 +378,13 @@ class DocAccessible : public HyperTextAccessibleWrap,
    */
   DocAccessibleChild* IPCDoc() const { return mIPCDoc; }
 
+  /**
+   * Notify the document that a DOM node has been scrolled. document will
+   * dispatch throttled accessibility events for scrolling, and a scroll-end
+   * event.
+   */
+  void HandleScroll(nsINode* aTarget);
+
  protected:
   virtual ~DocAccessible();
 
@@ -418,12 +419,6 @@ class DocAccessible : public HyperTextAccessibleWrap,
    */
   void ProcessLoad();
 
-  /**
-   * Add/remove scroll listeners, @see nsIScrollPositionListener interface.
-   */
-  void AddScrollListener();
-  void RemoveScrollListener();
-
   /**
    * Append the given document accessible to this document's child document
    * accessibles.
@@ -577,7 +572,7 @@ class DocAccessible : public HyperTextAccessibleWrap,
    */
   static void ScrollTimerCallback(nsITimer* aTimer, void* aClosure);
 
-  void DispatchScrollingEvent(uint32_t aEventType);
+  void DispatchScrollingEvent(nsINode* aTarget, uint32_t aEventType);
 
   /**
    * Check if an id attribute change affects aria-activedescendant and handle
@@ -607,11 +602,8 @@ class DocAccessible : public HyperTextAccessibleWrap,
    * State and property flags, kept by mDocFlags.
    */
   enum {
-    // Whether scroll listeners were added.
-    eScrollInitialized = 1 << 0,
-
     // Whether the document is a tab document.
-    eTabDocument = 1 << 1
+    eTabDocument = 1 << 0
   };
 
   /**
@@ -623,8 +615,7 @@ class DocAccessible : public HyperTextAccessibleWrap,
 
   Document* mDocumentNode;
   nsCOMPtr<nsITimer> mScrollWatchTimer;
-  uint16_t mScrollPositionChangedTicks;  // Used for tracking scroll events
-  TimeStamp mLastScrollingDispatch;
+  nsDataHashtable<nsPtrHashKey<nsINode>, TimeStamp> mLastScrollingDispatch;
 
   /**
    * Bit mask of document load states (@see LoadState).

accessible/generic/RootAccessible.cpp

@@ -144,7 +144,7 @@ const char* const kEventTypes[] = {
     // HTMLInputElement.cpp & radio.js)
     "RadioStateChange", "popupshown", "popuphiding", "DOMMenuInactive",
     "DOMMenuItemActive", "DOMMenuItemInactive", "DOMMenuBarActive",
-    "DOMMenuBarInactive"};
+    "DOMMenuBarInactive", "scroll"};
 
 nsresult RootAccessible::AddEventListeners() {
   // EventTarget interface allows to register event listeners to
@@ -222,13 +222,23 @@ RootAccessible::HandleEvent(Event* aDOMEvent) {
       GetAccService()->GetDocAccessible(origTargetNode->OwnerDoc());
 
   if (document) {
-    // Root accessible exists longer than any of its descendant documents so
-    // that we are guaranteed notification is processed before root accessible
-    // is destroyed.
-    // For shadow DOM, GetOriginalTarget on the Event returns null if we
-    // process the event async, so we must pass the target node as well.
-    document->HandleNotification<RootAccessible, Event, nsINode>(
-        this, &RootAccessible::ProcessDOMEvent, aDOMEvent, origTargetNode);
+    nsAutoString eventType;
+    aDOMEvent->GetType(eventType);
+    if (eventType.EqualsLiteral("scroll")) {
+      // We don't put this in the notification queue for 2 reasons:
+      // 1. We will flood the queue with repetitive events.
+      // 2. Since this doesn't necessarily touch layout, we are not
+      //    guaranteed to have a WillRefresh tick any time soon.
+      document->HandleScroll(origTargetNode);
+    } else {
+      // Root accessible exists longer than any of its descendant documents so
+      // that we are guaranteed notification is processed before root accessible
+      // is destroyed.
+      // For shadow DOM, GetOriginalTarget on the Event returns null if we
+      // process the event async, so we must pass the target node as well.
+      document->HandleNotification<RootAccessible, Event, nsINode>(
+          this, &RootAccessible::ProcessDOMEvent, aDOMEvent, origTargetNode);
+    }
   }
 
   return NS_OK;

accessible/tests/browser/events/browser_test_scrolling.js

@@ -8,7 +8,9 @@ addAccessibleTask(
   `
     <div style="height: 100vh" id="one">one</div>
     <div style="height: 100vh" id="two">two</div>
-    <div style="height: 100vh; width: 200vw" id="three">three</div>`,
+    <div style="height: 100vh; width: 200vw; overflow: auto;" id="three">
+      <div style="height: 300%;">three</div>
+    </div>`,
   async function(browser, accDoc) {
     let onScrolling = waitForEvents([
       [EVENT_SCROLLING, accDoc],
@@ -70,5 +72,25 @@ addAccessibleTask(
       scrollEvent3.scrollX > scrollEvent2.scrollX,
       `${scrollEvent3.scrollX} > ${scrollEvent2.scrollX}`
     );
+
+    // non-doc scrolling
+    onScrolling = waitForEvents([
+      [EVENT_SCROLLING, "three"],
+      [EVENT_SCROLLING_END, "three"],
+    ]);
+    await SpecialPowers.spawn(browser, [], () => {
+      content.document.querySelector("#three").scrollTo(0, 10);
+    });
+    let [scrollEvent4, scrollEndEvent4] = await onScrolling;
+    scrollEvent4.QueryInterface(nsIAccessibleScrollingEvent);
+    ok(
+      scrollEvent4.maxScrollY >= scrollEvent4.scrollY,
+      "scrollY is within max"
+    );
+    scrollEndEvent4.QueryInterface(nsIAccessibleScrollingEvent);
+    ok(
+      scrollEndEvent4.maxScrollY >= scrollEndEvent4.scrollY,
+      "scrollY is within max"
+    );
   }
 );