1 files changed, 142 insertions, 0 deletions
diff --git a/accessible/windows/msaa/LazyInstantiator.h b/accessible/windows/msaa/LazyInstantiator.h
new file mode 100644
index 0000000000..00fa4ba6ed
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+++ b/accessible/windows/msaa/LazyInstantiator.h
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=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/. */
+
+#ifndef mozilla_a11y_LazyInstantiator_h
+#define mozilla_a11y_LazyInstantiator_h
+
+#include "IUnknownImpl.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "nsString.h"
+
+#include <oleacc.h>
+
+class nsIFile;
+
+namespace mozilla {
+namespace a11y {
+
+class MsaaRootAccessible;
+
+/**
+ * LazyInstantiator is an IAccessible that initially acts as a placeholder.
+ * The a11y service is not actually started until two conditions are met:
+ *
+ * (1) A method is called on the LazyInstantiator that would require a11y
+ *     services in order to fulfill; and
+ * (2) LazyInstantiator::ShouldInstantiate returns true.
+ */
+class LazyInstantiator final : public IAccessible, public IServiceProvider {
+ public:
+  [[nodiscard]] static already_AddRefed<IAccessible> GetRootAccessible(
+      HWND aHwnd);
+  static void EnableBlindAggregation(HWND aHwnd);
+
+  // IUnknown
+  STDMETHODIMP QueryInterface(REFIID aIid, void** aOutInterface) override;
+  STDMETHODIMP_(ULONG) AddRef() override;
+  STDMETHODIMP_(ULONG) Release() override;
+
+  // IDispatch
+  STDMETHODIMP GetTypeInfoCount(UINT* pctinfo) override;
+  STDMETHODIMP GetTypeInfo(UINT iTInfo, LCID lcid,
+                           ITypeInfo** ppTInfo) override;
+  STDMETHODIMP GetIDsOfNames(REFIID riid, LPOLESTR* rgszNames, UINT cNames,
+                             LCID lcid, DISPID* rgDispId) override;
+  STDMETHODIMP Invoke(DISPID dispIdMember, REFIID riid, LCID lcid, WORD wFlags,
+                      DISPPARAMS* pDispParams, VARIANT* pVarResult,
+                      EXCEPINFO* pExcepInfo, UINT* puArgErr) override;
+
+  // IAccessible
+  STDMETHODIMP get_accParent(IDispatch** ppdispParent) override;
+  STDMETHODIMP get_accChildCount(long* pcountChildren) override;
+  STDMETHODIMP get_accChild(VARIANT varChild, IDispatch** ppdispChild) override;
+  STDMETHODIMP get_accName(VARIANT varChild, BSTR* pszName) override;
+  STDMETHODIMP get_accValue(VARIANT varChild, BSTR* pszValue) override;
+  STDMETHODIMP get_accDescription(VARIANT varChild,
+                                  BSTR* pszDescription) override;
+  STDMETHODIMP get_accRole(VARIANT varChild, VARIANT* pvarRole) override;
+  STDMETHODIMP get_accState(VARIANT varChild, VARIANT* pvarState) override;
+  STDMETHODIMP get_accHelp(VARIANT varChild, BSTR* pszHelp) override;
+  STDMETHODIMP get_accHelpTopic(BSTR* pszHelpFile, VARIANT varChild,
+                                long* pidTopic) override;
+  STDMETHODIMP get_accKeyboardShortcut(VARIANT varChild,
+                                       BSTR* pszKeyboardShortcut) override;
+  STDMETHODIMP get_accFocus(VARIANT* pvarChild) override;
+  STDMETHODIMP get_accSelection(VARIANT* pvarChildren) override;
+  STDMETHODIMP get_accDefaultAction(VARIANT varChild,
+                                    BSTR* pszDefaultAction) override;
+  STDMETHODIMP accSelect(long flagsSelect, VARIANT varChild) override;
+  STDMETHODIMP accLocation(long* pxLeft, long* pyTop, long* pcxWidth,
+                           long* pcyHeight, VARIANT varChild) override;
+  STDMETHODIMP accNavigate(long navDir, VARIANT varStart,
+                           VARIANT* pvarEndUpAt) override;
+  STDMETHODIMP accHitTest(long xLeft, long yTop, VARIANT* pvarChild) override;
+  STDMETHODIMP accDoDefaultAction(VARIANT varChild) override;
+  STDMETHODIMP put_accName(VARIANT varChild, BSTR szName) override;
+  STDMETHODIMP put_accValue(VARIANT varChild, BSTR szValue) override;
+
+  // IServiceProvider
+  STDMETHODIMP QueryService(REFGUID aServiceId, REFIID aServiceIid,
+                            void** aOutInterface) override;
+
+  /**
+   * We cache the result of UIA detection because it could be expensive if a
+   * client repeatedly queries us. This function is called to reset that cache
+   * when one of our windows comes to the foreground. If there is a new UIA
+   * client that isn't blocked, instantiation will subsequently be allowed. The
+   * hope is that a user will probably need to switch apps in order to start a
+   * new client.
+   */
+  static void ResetUiaDetectionCache() { sShouldBlockUia = Nothing(); }
+
+ private:
+  explicit LazyInstantiator(HWND aHwnd);
+  ~LazyInstantiator();
+
+  bool IsBlockedInjection();
+  bool ShouldInstantiate(const DWORD aClientPid);
+  bool ShouldInstantiate();
+
+  DWORD GetRemoteMsaaClientPid();
+
+  /**
+   * @return S_OK if we have a valid mRealRoot to invoke methods on
+   */
+  HRESULT MaybeResolveRoot();
+
+  /**
+   * @return S_OK if we have a valid mWeakDispatch to invoke methods on
+   */
+  HRESULT ResolveDispatch();
+
+  MsaaRootAccessible* ResolveMsaaRoot();
+  void TransplantRefCnt();
+  void ClearProp();
+
+ private:
+  mozilla::a11y::AutoRefCnt mRefCnt;
+  HWND mHwnd;
+  bool mAllowBlindAggregation;
+  RefPtr<IUnknown> mRealRootUnk;
+  RefPtr<IUnknown> mStdDispatch;
+  /**
+   * mWeakMsaaRoot, mWeakAccessible and mWeakDispatch are weak because they
+   * are interfaces that come from objects that we aggregate. Aggregated object
+   * interfaces share refcount methods with ours, so if we were to hold strong
+   * references to them, we would be holding strong references to ourselves,
+   * creating a cycle.
+   */
+  MsaaRootAccessible* mWeakMsaaRoot;
+  IAccessible* mWeakAccessible;
+  IDispatch* mWeakDispatch;
+  static Maybe<bool> sShouldBlockUia;
+};
+
+}  // namespace a11y
+}  // namespace mozilla
+
+#endif  // mozilla_a11y_LazyInstantiator_h