1 files changed, 87 insertions, 0 deletions
diff --git a/accessible/windows/msaa/MsaaIdGenerator.cpp b/accessible/windows/msaa/MsaaIdGenerator.cpp
new file mode 100644
index 0000000000..9f220365e3
--- /dev/null
+++ b/accessible/windows/msaa/MsaaIdGenerator.cpp
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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 "MsaaIdGenerator.h"
+
+#include "mozilla/a11y/MsaaAccessible.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Unused.h"
+#include "nsAccessibilityService.h"
+#include "sdnAccessible.h"
+
+namespace mozilla {
+namespace a11y {
+
+uint32_t MsaaIdGenerator::GetID() {
+  if (!mGetIDCalled) {
+    mGetIDCalled = true;
+    // this is a static instance, so capturing this here is safe.
+    RunOnShutdown([this] {
+      if (mReleaseIDTimer) {
+        mReleaseIDTimer->Cancel();
+        ReleasePendingIDs();
+      }
+    });
+  }
+  uint32_t id = mIDSet.GetID();
+  MOZ_ASSERT(id <= ((1UL << kNumFullIDBits) - 1UL));
+  return ~id;
+}
+
+void MsaaIdGenerator::ReleasePendingIDs() {
+  for (auto id : mIDsToRelease) {
+    mIDSet.ReleaseID(~id);
+  }
+  mIDsToRelease.Clear();
+  mReleaseIDTimer = nullptr;
+}
+
+bool MsaaIdGenerator::ReleaseID(uint32_t aID) {
+  MOZ_ASSERT(aID != MsaaAccessible::kNoID);
+  // Releasing an id means it can be reused. Reusing ids too quickly can
+  // cause problems for clients which process events asynchronously.
+  // Therefore, we release ids after a short delay. This doesn't seem to be
+  // necessary when the cache is disabled, perhaps because the COM runtime
+  // holds references to our objects for longer.
+  if (nsAccessibilityService::IsShutdown()) {
+    // If accessibility is shut down, no more Accessibles will be created.
+    // Also, if the service is shut down, it's possible XPCOM is also shutting
+    // down, in which case timers won't work. Thus, we release the id
+    // immediately.
+    mIDSet.ReleaseID(~aID);
+    return true;
+  }
+  const uint32_t kReleaseDelay = 1000;
+  mIDsToRelease.AppendElement(aID);
+  if (mReleaseIDTimer) {
+    mReleaseIDTimer->SetDelay(kReleaseDelay);
+  } else {
+    NS_NewTimerWithCallback(
+        getter_AddRefs(mReleaseIDTimer),
+        // mReleaseIDTimer is cancelled on shutdown and this is a static
+        // instance, so capturing this here is safe.
+        [this](nsITimer* aTimer) { ReleasePendingIDs(); }, kReleaseDelay,
+        nsITimer::TYPE_ONE_SHOT, "a11y::MsaaIdGenerator::ReleaseIDDelayed");
+  }
+  return true;
+}
+
+void MsaaIdGenerator::ReleaseID(NotNull<MsaaAccessible*> aMsaaAcc) {
+  ReleaseID(aMsaaAcc->GetExistingID());
+}
+
+void MsaaIdGenerator::ReleaseID(NotNull<sdnAccessible*> aSdnAcc) {
+  Maybe<uint32_t> id = aSdnAcc->ReleaseUniqueID();
+  if (id.isSome()) {
+    DebugOnly<bool> released = ReleaseID(id.value());
+    MOZ_ASSERT(released);
+  }
+}
+
+}  // namespace a11y
+}  // namespace mozilla