AX: WebKit does not break AX modality when focus is explicitly moved …

…outside the modal

https://bugs.webkit.org/show_bug.cgi?id=246580
rdar://problem/101209793

Reviewed by Chris Fleizach.

https://www.w3.org/TR/wai-aria-1.1/#aria-modal

"If focus moves to an element outside the modal element, assistive technologies SHOULD NOT limit navigation to the modal element."

With this patch, we now follow this recommendation.

* LayoutTests/accessibility/aria-modal-multiple-dialogs-expected.txt:
* LayoutTests/accessibility/aria-modal-multiple-dialogs.html:
* Source/WebCore/accessibility/AXObjectCache.cpp:
(WebCore::AXObjectCache::updateCurrentModalNode):
(WebCore::AXObjectCache::updateCurrentModalNodeInternal):
Deleted. Function body moved to a lambda inside updateCurrentModalNode.
(WebCore::AXObjectCache::performDeferredCacheUpdate):
* Source/WebCore/accessibility/AXObjectCache.h:

Canonical link: https://commits.webkit.org/255665@main

LayoutTests/accessibility/aria-modal-multiple-dialogs-expected.txt

@@ -22,6 +22,10 @@ PASS: background accessible: false
 PASS: #dialog1 accessible: true
 PASS: #dialog2 accessible: false
 
+Focusing on background.
+
+PASS: background accessible: true
+
 Moving focus back to first descendant of #dialog2.
 
 PASS: background accessible: false

LayoutTests/accessibility/aria-modal-multiple-dialogs.html

@@ -51,6 +51,12 @@ <h3 id="description2">Another dialog.</h3>
             await dialog1Accessible(true);
             await dialog2Accessible(false);
 
+            // https://www.w3.org/TR/wai-aria-1.1/#aria-modal
+            // "If focus moves to an element outside the modal element, assistive technologies SHOULD NOT limit navigation to the modal element."
+            testOutput += "\nFocusing on background.\n\n";
+            document.getElementById("textfield").focus();
+            await backgroundAccessible(true);
+
             testOutput += "\nMoving focus back to first descendant of #dialog2.\n\n";
             focusFirstDescendant(document.getElementById("dialog2"));
             await backgroundAccessible(false);

Source/WebCore/accessibility/AXObjectCache.cpp

@@ -309,10 +309,52 @@ bool AXObjectCache::modalElementHasAccessibleContent(Element& element)
     return false;
 }
 
-void AXObjectCache::updateCurrentModalNode()
+void AXObjectCache::updateCurrentModalNode(WillRecomputeFocus willRecomputeFocus)
 {
+    auto recomputeModalElement = [&] () -> Element* {
+        // There might be multiple modal dialog nodes.
+        // We use this function to pick the one we want.
+        if (m_modalElements.isEmpty())
+            return nullptr;
+
+        // Pick the document active modal <dialog> element if it exists.
+        if (Element* activeModalDialog = document().activeModalDialog()) {
+            ASSERT(m_modalElements.contains(activeModalDialog));
+            return activeModalDialog;
+        }
+
+        SetForScope retrievingCurrentModalNode(m_isRetrievingCurrentModalNode, true);
+        // If any of the modal nodes contains the keyboard focus, we want to pick that one.
+        // If not, we want to pick the last visible dialog in the DOM.
+        RefPtr<Element> focusedElement = document().focusedElement();
+        bool focusedElementIsOutsideModals = focusedElement;
+        RefPtr<Element> lastVisible;
+        for (auto& element : m_modalElements) {
+            // Elements in m_modalElementsSet may have become un-modal since we added them, but not yet removed
+            // as part of the asynchronous m_deferredModalChangedList handling. Skip these.
+            if (!element || !isModalElement(*element))
+                continue;
+
+            // To avoid trapping users in an empty modal, skip any non-visible element, or any element without accessible content.
+            if (!isNodeVisible(element.get()) || !modalElementHasAccessibleContent(*element))
+                continue;
+
+            lastVisible = element.get();
+            if (focusedElement && focusedElement->isDescendantOf(*element)) {
+                focusedElementIsOutsideModals = false;
+                break;
+            }
+        }
+
+        // If there is a focused element, and it's not inside any of the modals, we should
+        // consider all modals inactive to allow the user to freely navigate.
+        if (focusedElementIsOutsideModals && willRecomputeFocus == WillRecomputeFocus::No)
+            return nullptr;
+        return lastVisible.get();
+    };
+
     auto* previousModal = m_currentModalElement.get();
-    m_currentModalElement = updateCurrentModalNodeInternal();
+    m_currentModalElement = recomputeModalElement();
     if (previousModal != m_currentModalElement.get()) {
         childrenChanged(rootWebArea());
 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
@@ -323,41 +365,6 @@ void AXObjectCache::updateCurrentModalNode()
     }
 }
 
-Element* AXObjectCache::updateCurrentModalNodeInternal()
-{
-    // There might be multiple modal dialog nodes.
-    // We use this function to pick the one we want.
-    if (m_modalElements.isEmpty())
-        return nullptr;
-
-    // Pick the document active modal <dialog> element if it exists.
-    if (Element* activeModalDialog = document().activeModalDialog()) {
-        ASSERT(m_modalElements.contains(activeModalDialog));
-        return activeModalDialog;
-    }
-
-    SetForScope retrievingCurrentModalNode(m_isRetrievingCurrentModalNode, true);
-    // If any of the modal nodes contains the keyboard focus, we want to pick that one.
-    // If not, we want to pick the last visible dialog in the DOM.
-    RefPtr<Element> focusedElement = document().focusedElement();
-    RefPtr<Element> lastVisible;
-    for (auto& element : m_modalElements) {
-        // Elements in m_modalElementsSet may have become un-modal since we added them, but not yet removed
-        // as part of the asynchronous m_deferredModalChangedList handling. Skip these.
-        if (!element || !isModalElement(*element))
-            continue;
-
-        // To avoid trapping users in an empty modal, skip any non-visible element, or any element without accessible content.
-        if (!isNodeVisible(element.get()) || !modalElementHasAccessibleContent(*element))
-            continue;
-
-        lastVisible = element.get();
-        if (focusedElement && focusedElement->isDescendantOf(*element))
-            break;
-    }
-    return lastVisible.get();
-}
-
 bool AXObjectCache::isNodeVisible(Node* node) const
 {
     if (!is<Element>(node))
@@ -3576,7 +3583,7 @@ void AXObjectCache::performDeferredCacheUpdate()
     m_deferredModalChangedList.clear();
 
     if (shouldRecomputeModal) {
-        updateCurrentModalNode();
+        updateCurrentModalNode(updatedFocusedElement ? WillRecomputeFocus::No : WillRecomputeFocus::Yes);
         // "When a modal element is displayed, assistive technologies SHOULD navigate to the element unless focus has explicitly been set elsewhere."
         // `updatedFocusedElement` indicates focus was explicitly set elsewhere, so don't autofocus into the modal.
         // https://w3c.github.io/aria/#aria-modal

Source/WebCore/accessibility/AXObjectCache.h

@@ -513,8 +513,8 @@ class AXObjectCache {
     // aria-modal or modal <dialog> related
     bool isModalElement(Element&) const;
     void findModalNodes();
-    void updateCurrentModalNode();
-    Element* updateCurrentModalNodeInternal();
+    enum class WillRecomputeFocus : bool { No, Yes };
+    void updateCurrentModalNode(WillRecomputeFocus = WillRecomputeFocus::No);
     bool isNodeVisible(Node*) const;
     bool modalElementHasAccessibleContent(Element&);