Improve support for multiselect list box accessibility on Windows.

base/win/enum_variant.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/logging.h"
+#include "base/win/enum_variant.h"
+
+namespace base {
+namespace win {
+
+EnumVariant::EnumVariant(unsigned long count)
+    : count_(count) {
+  items_.reset(new VARIANT[count_]);
+  current_index_ = 0;
+  ref_count_ = 1;
+}
+
+EnumVariant::~EnumVariant() {
+}
+
+VARIANT* EnumVariant::ItemAt(unsigned long index) {
+  DCHECK(index < count_);
+  return &items_[index];
+}
+
+ULONG STDMETHODCALLTYPE EnumVariant::AddRef() {
+  return InterlockedIncrement(&ref_count_);
+}
+
+ULONG STDMETHODCALLTYPE EnumVariant::Release() {
+  ULONG ref_count = InterlockedDecrement(&ref_count_);
+  if (ref_count == 0)
+    delete this;
+  return ref_count;
+}
+
+STDMETHODIMP EnumVariant::QueryInterface(REFIID riid, void** ppv) {
+  if (riid == IID_IUnknown ||
+      riid == IID_IEnumVARIANT) {
+    *ppv = this;
+    AddRef();
+    return S_OK;
+  }
+
+  *ppv = NULL;
+  return E_NOINTERFACE;
+}
+
+STDMETHODIMP EnumVariant::Next(ULONG requested_count,
+                               VARIANT* out_elements,
+                               ULONG* out_elements_received) {
+  unsigned long count = requested_count;
+  if (current_index_ + count > count_)
+    count = count_ - current_index_;
+
+  for (unsigned long i = 0; i < count; ++i)
+    out_elements[i] = items_[current_index_ + i];
+  current_index_ += count;
+  *out_elements_received = count;
+
+  return (count == requested_count ? S_OK : S_FALSE);
+}
+
+STDMETHODIMP EnumVariant::Skip(ULONG skip_count) {
+  unsigned long count = skip_count;
+  if (current_index_ + count > count_)
+    count = count_ - current_index_;
+
+  current_index_ += count;
+  return (count == skip_count ? S_OK : S_FALSE);
+}
+
+STDMETHODIMP EnumVariant::Reset() {
+  current_index_ = 0;
+  return S_OK;
+}
+
+STDMETHODIMP EnumVariant::Clone(IEnumVARIANT** out_cloned_object) {
+  EnumVariant* other = new EnumVariant(count_);
+  for (unsigned long i = 0; i < count_; ++i)
+    *other->ItemAt(i) = items_[i];
+  *out_cloned_object = other;
+  return S_OK;
+}
+
+}  // namespace win
+}  // namespace base