Windows: Introduce helper class for implementing COM interfaces

Task-number: QTBUG-43190
Change-Id: I565e3c57631c32a88ac7598758526c349ddf3312
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

4 files changed, 63 insertions, 192 deletions

diff --git a/src/plugins/platforms/windows/accessible/iaccessible2.cpp b/src/plugins/platforms/windows/accessible/iaccessible2.cpp
index d5cd9ac6db..9295fceff5 100644
--- a/src/plugins/platforms/windows/accessible/iaccessible2.cpp
+++ b/src/plugins/platforms/windows/accessible/iaccessible2.cpp
@@ -61,40 +61,7 @@ static inline T *coTaskMemAllocArray(int size)
 /**************************************************************\
  *                     AccessibleApplication                  *
  **************************************************************/
-//  IUnknown
-HRESULT STDMETHODCALLTYPE AccessibleApplication::QueryInterface(REFIID id, LPVOID *iface)
-{
-    *iface = 0;
-    if (id == IID_IUnknown) {
-        qCDebug(lcQpaAccessibility) << "AccessibleApplication::QI(): IID_IUnknown";
-        *iface = static_cast<IUnknown *>(this);
-    } else if (id == IID_IAccessibleApplication) {
-        qCDebug(lcQpaAccessibility) << "AccessibleApplication::QI(): IID_IAccessibleApplication";
-        *iface = static_cast<IAccessibleApplication*>(this);
-    }
-
-    if (*iface) {
-        AddRef();
-        return S_OK;
-    }
-    return E_NOINTERFACE;
-}
 
-ULONG STDMETHODCALLTYPE AccessibleApplication::AddRef()
-{
-    return ++m_ref;
-}
-
-ULONG STDMETHODCALLTYPE AccessibleApplication::Release()
-{
-    if (!--m_ref) {
-        delete this;
-        return 0;
-    }
-    return m_ref;
-}
-
-/* IAccessibleApplication */
 HRESULT STDMETHODCALLTYPE AccessibleApplication::get_appName(/* [retval][out] */ BSTR *name)
 {
     const QString appName = QGuiApplication::applicationName();
@@ -127,40 +94,11 @@ HRESULT STDMETHODCALLTYPE AccessibleApplication::get_toolkitVersion(/* [retval][
  **************************************************************/
 AccessibleRelation::AccessibleRelation(const QList<QAccessibleInterface *> &targets,
                     QAccessible::Relation relation)
-    : m_targets(targets), m_relation(relation), m_ref(1)
+    : m_targets(targets), m_relation(relation)
 {
     Q_ASSERT(m_targets.count());
 }
 
-/* IUnknown */
-HRESULT STDMETHODCALLTYPE AccessibleRelation::QueryInterface(REFIID id, LPVOID *iface)
-{
-    *iface = 0;
-    if (id == IID_IUnknown || id == IID_IAccessibleRelation)
-        *iface = static_cast<IUnknown *>(this);
-
-    if (*iface) {
-        AddRef();
-        return S_OK;
-    }
-
-    return E_NOINTERFACE;
-}
-
-ULONG STDMETHODCALLTYPE AccessibleRelation::AddRef()
-{
-    return ++m_ref;
-}
-
-ULONG STDMETHODCALLTYPE AccessibleRelation::Release()
-{
-    if (!--m_ref) {
-        delete this;
-        return 0;
-    }
-    return m_ref;
-}
-
 /* IAccessibleRelation */
 HRESULT STDMETHODCALLTYPE AccessibleRelation::get_relationType(
     /* [retval][out] */ BSTR *relationType)
@@ -237,56 +175,53 @@ HRESULT STDMETHODCALLTYPE AccessibleRelation::get_targets(
  **************************************************************/
 HRESULT STDMETHODCALLTYPE QWindowsIA2Accessible::QueryInterface(REFIID id, LPVOID *iface)
 {
+    *iface = nullptr;
     QAccessibleInterface *accessible = accessibleInterface();
     if (!accessible)
         return E_NOINTERFACE;
 
-    HRESULT hr = QWindowsMsaaAccessible::QueryInterface(id, iface);
-    if (!SUCCEEDED(hr)) {
-        if (id == IID_IServiceProvider) {
-            *iface = static_cast<IServiceProvider *>(this);
-        } else if (id == IID_IAccessible2) {
-            *iface = static_cast<IAccessible2 *>(this);
-        } else if (id == IID_IAccessibleAction) {
-            if (accessible->actionInterface())
-                *iface = static_cast<IAccessibleAction *>(this);
-        } else if (id == IID_IAccessibleComponent) {
-            *iface = static_cast<IAccessibleComponent *>(this);
-        } else if (id == IID_IAccessibleEditableText) {
-            if (accessible->editableTextInterface() ||
-                accessible->role() == QAccessible::EditableText)
-            {
-                *iface = static_cast<IAccessibleEditableText *>(this);
-            }
-        } else if (id == IID_IAccessibleHyperlink) {
-            //*iface = static_cast<IAccessibleHyperlink *>(this);
-        } else if (id == IID_IAccessibleHypertext) {
-            //*iface = static_cast<IAccessibleHypertext *>(this);
-        } else if (id == IID_IAccessibleImage) {
-            //*iface = static_cast<IAccessibleImage *>(this);
-        } else if (id == IID_IAccessibleTable) {
-            //*iface = static_cast<IAccessibleTable *>(this); // not supported
-        } else if (id == IID_IAccessibleTable2) {
-            if (accessible->tableInterface())
-                *iface = static_cast<IAccessibleTable2 *>(this);
-        } else if (id == IID_IAccessibleTableCell) {
-            if (accessible->tableCellInterface())
-                *iface = static_cast<IAccessibleTableCell *>(this);
-        } else if (id == IID_IAccessibleText) {
-            if (accessible->textInterface())
-                *iface = static_cast<IAccessibleText *>(this);
-        } else if (id == IID_IAccessibleValue) {
-            if (accessible->valueInterface())
-                *iface = static_cast<IAccessibleValue *>(this);
-        }
-        if (*iface) {
-            AddRef();
-            hr = S_OK;
-        } else {
-            hr = E_NOINTERFACE;
+    if (SUCCEEDED(QWindowsMsaaAccessible::QueryInterface(id, iface))
+        || qWindowsComQueryInterface<IServiceProvider>(this, id, iface)
+        || qWindowsComQueryInterface<IAccessible2>(this, id, iface)
+        || qWindowsComQueryInterface<IAccessibleComponent>(this, id, iface)) {
+        return S_OK;
+    }
+
+    if (id == IID_IAccessibleAction) {
+        if (accessible->actionInterface())
+            *iface = static_cast<IAccessibleAction *>(this);
+    } else if (id == IID_IAccessibleEditableText) {
+        if (accessible->editableTextInterface() ||
+            accessible->role() == QAccessible::EditableText)
+        {
+            *iface = static_cast<IAccessibleEditableText *>(this);
         }
+    } else if (id == IID_IAccessibleHyperlink) {
+        //*iface = static_cast<IAccessibleHyperlink *>(this);
+    } else if (id == IID_IAccessibleHypertext) {
+        //*iface = static_cast<IAccessibleHypertext *>(this);
+    } else if (id == IID_IAccessibleImage) {
+        //*iface = static_cast<IAccessibleImage *>(this);
+    } else if (id == IID_IAccessibleTable) {
+        //*iface = static_cast<IAccessibleTable *>(this); // not supported
+    } else if (id == IID_IAccessibleTable2) {
+        if (accessible->tableInterface())
+            *iface = static_cast<IAccessibleTable2 *>(this);
+    } else if (id == IID_IAccessibleTableCell) {
+        if (accessible->tableCellInterface())
+            *iface = static_cast<IAccessibleTableCell *>(this);
+    } else if (id == IID_IAccessibleText) {
+        if (accessible->textInterface())
+            *iface = static_cast<IAccessibleText *>(this);
+    } else if (id == IID_IAccessibleValue) {
+        if (accessible->valueInterface())
+            *iface = static_cast<IAccessibleValue *>(this);
     }
-    return hr;
+    if (*iface) {
+        AddRef();
+        return S_OK;
+    }
+    return E_NOINTERFACE;
 }
 
 
diff --git a/src/plugins/platforms/windows/accessible/iaccessible2.h b/src/plugins/platforms/windows/accessible/iaccessible2.h
index bc5f5be60f..17a22dd8c8 100644
--- a/src/plugins/platforms/windows/accessible/iaccessible2.h
+++ b/src/plugins/platforms/windows/accessible/iaccessible2.h
@@ -42,6 +42,7 @@
 #include <QtCore/QtConfig>
 #ifndef QT_NO_ACCESSIBILITY
 
+#include "qwindowscombase.h"
 #include "qwindowsmsaaaccessible.h"
 #include "comutils.h"
 
@@ -258,28 +259,18 @@ private:
 /**************************************************************\
  *                     AccessibleApplication                  *
  **************************************************************/
-class AccessibleApplication : public IAccessibleApplication
+class AccessibleApplication : public QWindowsComBase<IAccessibleApplication>
 {
 public:
-    AccessibleApplication() : m_ref(1)
-    {
-
-    }
+    AccessibleApplication() {}
 
     virtual ~AccessibleApplication() {}
 
-    /* IUnknown */
-    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID, LPVOID *);
-    ULONG STDMETHODCALLTYPE AddRef();
-    ULONG STDMETHODCALLTYPE Release();
-
     /* IAccessibleApplication */
     HRESULT STDMETHODCALLTYPE get_appName(/* [retval][out] */ BSTR *name);
     HRESULT STDMETHODCALLTYPE get_appVersion(/* [retval][out] */ BSTR *version);
     HRESULT STDMETHODCALLTYPE get_toolkitName(/* [retval][out] */ BSTR *name);
     HRESULT STDMETHODCALLTYPE get_toolkitVersion(/* [retval][out] */ BSTR *version);
-private:
-    ULONG m_ref;
 };
 
 
@@ -287,7 +278,7 @@ private:
 /**************************************************************\
  *                     AccessibleRelation                      *
  **************************************************************/
-class AccessibleRelation : public IAccessibleRelation
+class AccessibleRelation : public QWindowsComBase<IAccessibleRelation>
 {
 public:
     AccessibleRelation(const QList<QAccessibleInterface *> &targets,
@@ -295,11 +286,6 @@ public:
 
     virtual ~AccessibleRelation() {}
 
-    /* IUnknown */
-    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID id, LPVOID *iface);
-    ULONG STDMETHODCALLTYPE AddRef();
-    ULONG STDMETHODCALLTYPE Release();
-
     /* IAccessibleRelation */
     HRESULT STDMETHODCALLTYPE get_relationType(BSTR *relationType);
     HRESULT STDMETHODCALLTYPE get_localizedRelationType(BSTR *localizedRelationType);
@@ -341,7 +327,6 @@ private:
 
     QList<QAccessibleInterface *> m_targets;
     QAccessible::Relation m_relation;
-    ULONG m_ref;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.cpp b/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.cpp
index 25b1577772..0ee956c865 100644
--- a/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.cpp
+++ b/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.cpp
@@ -42,6 +42,7 @@
 
 #include "qwindowsmsaaaccessible.h"
 #include "qwindowsaccessibility.h"
+#include "qwindowscombase.h"
 #include <oleacc.h>
 #include <servprov.h>
 #include <winuser.h>
@@ -71,61 +72,22 @@
 
 QT_BEGIN_NAMESPACE
 
-class QWindowsEnumerate : public IEnumVARIANT
+class QWindowsEnumerate : public QWindowsComBase<IEnumVARIANT>
 {
 public:
-    QWindowsEnumerate(const QVector<int> &a)
-        : ref(0), current(0),array(a)
-    {
-    }
-
+    QWindowsEnumerate(const QVector<int> &a) : QWindowsComBase<IEnumVARIANT>(0), current(0),array(a) {}
     virtual ~QWindowsEnumerate() {}
 
-    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID, LPVOID *);
-    ULONG STDMETHODCALLTYPE AddRef();
-    ULONG STDMETHODCALLTYPE Release();
-
     HRESULT STDMETHODCALLTYPE Clone(IEnumVARIANT **ppEnum);
     HRESULT STDMETHODCALLTYPE Next(unsigned long  celt, VARIANT FAR*  rgVar, unsigned long FAR*  pCeltFetched);
     HRESULT STDMETHODCALLTYPE Reset();
     HRESULT STDMETHODCALLTYPE Skip(unsigned long celt);
 
 private:
-    ULONG ref;
     ULONG current;
     QVector<int> array;
 };
 
-HRESULT STDMETHODCALLTYPE QWindowsEnumerate::QueryInterface(REFIID id, LPVOID *iface)
-{
-    *iface = 0;
-    if (id == IID_IUnknown)
-        *iface = static_cast<IUnknown *>(this);
-    else if (id == IID_IEnumVARIANT)
-        *iface = static_cast<IEnumVARIANT *>(this);
-
-    if (*iface) {
-        AddRef();
-        return S_OK;
-    }
-
-    return E_NOINTERFACE;
-}
-
-ULONG STDMETHODCALLTYPE QWindowsEnumerate::AddRef()
-{
-    return ++ref;
-}
-
-ULONG STDMETHODCALLTYPE QWindowsEnumerate::Release()
-{
-    if (!--ref) {
-        delete this;
-        return 0;
-    }
-    return ref;
-}
-
 HRESULT STDMETHODCALLTYPE QWindowsEnumerate::Clone(IEnumVARIANT **ppEnum)
 {
     QWindowsEnumerate *penum = 0;
@@ -193,29 +155,17 @@ void accessibleDebugClientCalls_helper(const char* funcName, const QAccessibleIn
  **************************************************************/
 HRESULT STDMETHODCALLTYPE QWindowsMsaaAccessible::QueryInterface(REFIID id, LPVOID *iface)
 {
-    *iface = 0;
+    *iface = nullptr;
+    const bool result = qWindowsComQueryUnknownInterfaceMulti<AccessibleBase>(this, id, iface)
+        || qWindowsComQueryInterface<IDispatch>(this, id, iface)
+        || qWindowsComQueryInterface<IAccessible>(this, id, iface)
+        || qWindowsComQueryInterface<IOleWindow>(this, id, iface);
 
-    QByteArray strIID = IIDToString(id);
-    if (!strIID.isEmpty()) {
+    if (result) {
         qCDebug(lcQpaAccessibility) << "QWindowsIA2Accessible::QI() - IID:"
-                                    << strIID << ", iface:" << accessibleInterface();
-    }
-    if (id == IID_IUnknown) {
-        *iface =  static_cast<IUnknown *>(static_cast<IDispatch *>(this));
-    } else if (id == IID_IDispatch) {
-        *iface = static_cast<IDispatch *>(this);
-    } else if (id == IID_IAccessible) {
-        *iface = static_cast<IAccessible *>(this);
-    } else if (id == IID_IOleWindow) {
-        *iface = static_cast<IOleWindow *>(this);
-    }
-
-    if (*iface) {
-        AddRef();
-        return S_OK;
+            << IIDToString(id) << ", iface:" << accessibleInterface();
     }
-
-    return E_NOINTERFACE;
+    return result ? S_OK : E_NOINTERFACE;
 }
 
 ULONG STDMETHODCALLTYPE QWindowsMsaaAccessible::AddRef()
diff --git a/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.h b/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.h
index fd00f8ac8b..138e71877b 100644
--- a/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.h
+++ b/src/plugins/platforms/windows/accessible/qwindowsmsaaaccessible.h
@@ -72,13 +72,14 @@ QWindow *window_helper(const QAccessibleInterface *iface);
 /**************************************************************\
  *                     QWindowsAccessible                     *
  **************************************************************/
-class QWindowsMsaaAccessible : public
-#ifdef Q_CC_MINGW
-        IAccessible
+
+#ifndef Q_CC_MINGW
+typedef IAccessible2 AccessibleBase;
 #else
-        IAccessible2
+typedef IAccessible AccessibleBase;
 #endif
-        , public IOleWindow
+
+class QWindowsMsaaAccessible : public AccessibleBase, public IOleWindow
 {
 public:
     QWindowsMsaaAccessible(QAccessibleInterface *a)