Bug 1794974: Part 4: Add ability to easily query, request new cache domains,r=Jamie

This revision adds code that will make it simple to request new cache domains as
as response to assistive technology queries.

Differential Revision: https://phabricator.services.mozilla.com/D220038

Author: Nathan LaPre

accessible/base/CacheConstants.cpp

@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set expandtab shiftwidth=2 tabstop=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/. */
+
+#include "CacheConstants.h"
+#include "nsAccessibilityService.h"
+
+namespace mozilla::a11y {
+
+// Get the set of cache domains required by the given cache domains, which will
+// always be equal to or a superset of the given set of cache domains.
+static uint64_t GetCacheDomainSuperset(uint64_t aCacheDomains) {
+  uint64_t allNecessaryDomains = aCacheDomains;
+  if (aCacheDomains & CacheDomain::TextOffsetAttributes) {
+    allNecessaryDomains |= CacheDomain::Text;
+  }
+  if (aCacheDomains & CacheDomain::TextBounds) {
+    allNecessaryDomains |= CacheDomain::Text;
+    allNecessaryDomains |= CacheDomain::Bounds;
+  }
+  MOZ_ASSERT((allNecessaryDomains & aCacheDomains) == aCacheDomains,
+             "Return value is not a superset of the input.");
+  return allNecessaryDomains;
+}
+
+bool DomainsAreActive(uint64_t aRequiredCacheDomains) {
+  const uint64_t activeCacheDomains =
+      nsAccessibilityService::GetActiveCacheDomains();
+  const bool allRequiredDomainsAreActive =
+      (aRequiredCacheDomains & ~activeCacheDomains) == 0;
+  return allRequiredDomainsAreActive;
+}
+
+bool RequestDomainsIfInactive(uint64_t aRequiredCacheDomains) {
+  nsAccessibilityService* accService = GetAccService();
+  if (!accService) {
+    return true;
+  }
+  const uint64_t activeCacheDomains =
+      nsAccessibilityService::GetActiveCacheDomains();
+  const bool isMissingRequiredCacheDomain =
+      (aRequiredCacheDomains & ~activeCacheDomains) != 0;
+  if (isMissingRequiredCacheDomain) {
+    aRequiredCacheDomains = GetCacheDomainSuperset(aRequiredCacheDomains);
+
+    const uint64_t cacheDomains = aRequiredCacheDomains | activeCacheDomains;
+#if defined(ANDROID)
+    // We might not be on the main Android thread, but we must be in order to
+    // send IPDL messages. Dispatch to the main thread to set cache domains.
+    NS_DispatchToMainThread(
+        NS_NewRunnableFunction("a11y::SetCacheDomains", [cacheDomains]() {
+          if (nsAccessibilityService* accService = GetAccService()) {
+            accService->SetCacheDomains(cacheDomains);
+          }
+        }));
+    return true;
+#endif
+
+    accService->SetCacheDomains(cacheDomains);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace mozilla::a11y

accessible/base/CacheConstants.h

@@ -104,7 +104,7 @@ constexpr int32_t kNumbersInRect = 4;
  * cache should generally use these aliases rather than using nsAtoms directly.
  * There are two exceptions:
  * 1. Some ARIA attributes are copied directly from the DOM node, so these
- * aren't aliased. Specifically,   aria-level, aria-posinset and aria-setsize
+ * aren't aliased. Specifically, aria-level, aria-posinset and aria-setsize
  * are copied as separate cache keys as part of CacheDomain::GroupInfo.
  * 2. Keys for relations are defined in kRelationTypeAtoms above.
  */
@@ -257,6 +257,18 @@ class CacheKey {
   static constexpr nsStaticAtom* Viewport = nsGkAtoms::viewport;
 };
 
+// Return true if the given cache domains are already active.
+bool DomainsAreActive(uint64_t aRequiredCacheDomains);
+
+// Check whether the required cache domains are active. If they aren't, then
+// request the requisite cache domains and return true. This function returns
+// false if all required domains are already active.
+bool RequestDomainsIfInactive(uint64_t aRequiredCacheDomains);
+
+#define ASSERT_DOMAINS_ACTIVE(aCacheDomains)  \
+  MOZ_ASSERT(DomainsAreActive(aCacheDomains), \
+             "Required domain(s) are not currently active.")
+
 }  // namespace a11y
 }  // namespace mozilla
 

accessible/base/moz.build

@@ -47,6 +47,7 @@ UNIFIED_SOURCES += [
     "ARIAMap.cpp",
     "ARIAStateMap.cpp",
     "Asserts.cpp",
+    "CacheConstants.cpp",
     "CachedTableAccessible.cpp",
     "CssAltContent.cpp",
     "DocManager.cpp",