Bug 1816346 part 2: If we force an Accessible to be created due to transform/fixed/sticky despite it being presentational, make it a generic Accessible. r=nlapre

Otherwise, semantics are exposed (e.g. for a table), which completely defeats the author's intent that this be treated as presentational.

Differential Revision: https://phabricator.services.mozilla.com/D170165

accessible/base/nsAccessibilityService.cpp

@@ -112,20 +112,6 @@ static bool MustBeAccessible(nsIContent* aContent, DocAccessible* aDocument) {
     return true;
   }
 
-  // If the frame has been transformed, and the content has any children, we
-  // should create an Accessible so that we can account for the transform when
-  // calculating the Accessible's bounds using the parent process cache.
-  // Ditto for content which is position: fixed or sticky.
-  // However, don't do this for XUL widgets, as this breaks XUL a11y code
-  // expectations in some cases. XUL widgets are only used in the parent
-  // process and can't be cached anyway.
-  if (aContent->HasChildren() && !aContent->IsXULElement() &&
-      (frame->IsTransformed() || frame->IsStickyPositioned() ||
-       (frame->StyleDisplay()->mPosition == StylePositionProperty::Fixed &&
-        nsLayoutUtils::IsReallyFixedPos(frame)))) {
-    return true;
-  }
-
   if (aContent->IsElement()) {
     uint32_t attrCount = aContent->AsElement()->GetAttrCount();
     for (uint32_t attrIdx = 0; attrIdx < attrCount; attrIdx++) {
@@ -162,6 +148,34 @@ static bool MustBeAccessible(nsIContent* aContent, DocAccessible* aDocument) {
   return false;
 }
 
+/**
+ * Return true if the element must be a generic Accessible, even if it has been
+ * marked presentational with role="presentation", etc. MustBeAccessible causes
+ * an Accessible to be created as if it weren't marked presentational at all;
+ * e.g. <table role="presentation" tabindex="0"> will expose roles::TABLE and
+ * support TableAccessibleBase. In contrast, this function causes a generic
+ * Accessible to be created; e.g. <table role="presentation" style="position:
+ * fixed;"> will expose roles::TEXT_CONTAINER and will not support
+ * TableAccessibleBase. This is necessary in certain cases for the
+ * RemoteAccessible cache.
+ */
+static bool MustBeGenericAccessible(nsIContent* aContent,
+                                    DocAccessible* aDocument) {
+  nsIFrame* frame = aContent->GetPrimaryFrame();
+  MOZ_ASSERT(frame);
+  // If the frame has been transformed, and the content has any children, we
+  // should create an Accessible so that we can account for the transform when
+  // calculating the Accessible's bounds using the parent process cache.
+  // Ditto for content which is position: fixed or sticky.
+  // However, don't do this for XUL widgets, as this breaks XUL a11y code
+  // expectations in some cases. XUL widgets are only used in the parent
+  // process and can't be cached anyway.
+  return aContent->HasChildren() && !aContent->IsXULElement() &&
+         (frame->IsTransformed() || frame->IsStickyPositioned() ||
+          (frame->StyleDisplay()->mPosition == StylePositionProperty::Fixed &&
+           nsLayoutUtils::IsReallyFixedPos(frame)));
+}
+
 bool nsAccessibilityService::ShouldCreateImgAccessible(
     mozilla::dom::Element* aElement, DocAccessible* aDocument) {
   // The element must have a layout frame for us to proceed. If there is no
@@ -1110,14 +1124,23 @@ LocalAccessible* nsAccessibilityService::CreateAccessible(
 
   const nsRoleMapEntry* roleMapEntry = aria::GetRoleMap(content->AsElement());
 
-  // If the element is focusable or global ARIA attribute is applied to it or
-  // it is referenced by ARIA relationship then treat role="presentation" on
-  // the element as the role is not there.
   if (roleMapEntry && (roleMapEntry->Is(nsGkAtoms::presentation) ||
                        roleMapEntry->Is(nsGkAtoms::none))) {
-    if (!MustBeAccessible(content, document)) return nullptr;
-
-    roleMapEntry = nullptr;
+    if (MustBeAccessible(content, document)) {
+      // If the element is focusable, a global ARIA attribute is applied to it
+      // or it is referenced by an ARIA relationship, then treat
+      // role="presentation" on the element as if the role is not there.
+      roleMapEntry = nullptr;
+    } else if (MustBeGenericAccessible(content, document)) {
+      // Clear roleMapEntry so that we use the generic role specified below.
+      // Otherwise, we'd expose roles::NOTHING as specified for presentation in
+      // ARIAMap.
+      roleMapEntry = nullptr;
+      newAcc = new EnumRoleHyperTextAccessible<roles::TEXT_CONTAINER>(content,
+                                                                      document);
+    } else {
+      return nullptr;
+    }
   }
 
   if (!newAcc && content->IsHTMLElement()) {  // HTML accessibles
@@ -1304,6 +1327,9 @@ LocalAccessible* nsAccessibilityService::CreateAccessible(
       // Interesting generic non-HTML container
       newAcc = new AccessibleWrap(content, document);
     }
+  } else if (!newAcc && MustBeGenericAccessible(content, document)) {
+    newAcc = new EnumRoleHyperTextAccessible<roles::TEXT_CONTAINER>(content,
+                                                                    document);
   }
 
   if (newAcc) {

accessible/tests/browser/bounds/browser_test_simple_transform.js

@@ -131,7 +131,7 @@ addAccessibleTask(
 </div>
   `,
   async function(browser, docAcc) {
-    const tree = { SECTION: [{ PARAGRAPH: [{ TEXT_LEAF: [] }] }] };
+    const tree = { TEXT_CONTAINER: [{ PARAGRAPH: [{ TEXT_LEAF: [] }] }] };
 
     const divWithTransform = findAccessibleChildByID(docAcc, "container")
       .firstChild;
@@ -159,7 +159,7 @@ addAccessibleTask(
   `,
   async function(browser, docAcc) {
     let divToTransform = findAccessibleChildByID(docAcc, "div-to-transform");
-    ok(!divToTransform, "There should not be a section accessible.");
+    ok(!divToTransform, "There should not be a div accessible.");
 
     // Translate the div.
     await invokeContentTask(browser, [], () => {
@@ -171,7 +171,7 @@ addAccessibleTask(
     // Verify that the SECTION accessible appeared after we gave it a transform.
     divToTransform = findAccessibleChildByID(docAcc, "div-to-transform");
     const tree = {
-      SECTION: [{ PARAGRAPH: [{ TEXT_LEAF: [] }] }],
+      TEXT_CONTAINER: [{ PARAGRAPH: [{ TEXT_LEAF: [] }] }],
     };
     testAccessibleTree(divToTransform, tree);
 

accessible/tests/browser/scroll/browser_test_scroll_bounds.js

@@ -4,7 +4,11 @@
 
 "use strict";
 
-loadScripts({ name: "layout.js", dir: MOCHITESTS_DIR });
+/* import-globals-from ../../mochitest/role.js */
+loadScripts(
+  { name: "layout.js", dir: MOCHITESTS_DIR },
+  { name: "role.js", dir: MOCHITESTS_DIR }
+);
 requestLongerTimeout(2);
 
 const appUnitsPerDevPixel = 60;
@@ -320,13 +324,17 @@ addAccessibleTask(
  */
 addAccessibleTask(
   `
-<div id="fixed" role="presentation" style="position: fixed;">fixed</div>
+<table id="fixed" role="presentation" style="position: fixed;">
+  <tr><th>fixed</th></tr>
+</table>
 <div id="mutate" role="presentation">mutate</div>
 <hr style="height: 200vh;">
 <p>bottom</p>
   `,
   async function(browser, docAcc) {
-    ok(findAccessibleChildByID(docAcc, "fixed"), "fixed is accessible");
+    const fixed = findAccessibleChildByID(docAcc, "fixed");
+    ok(fixed, "fixed is accessible");
+    isnot(fixed.role, ROLE_TABLE, "fixed doesn't have ROLE_TABLE");
     ok(!findAccessibleChildByID(docAcc, "mutate"), "mutate inaccessible");
     info("Setting position: fixed on mutate");
     let shown = waitForEvent(EVENT_SHOW, "mutate");