Move QWebEngineCallback to core API and templatize CallbackDirectory

This undocumented helper template will also be utilized by the
core API since Chromium's content API heavily relies on callbacks.
To make the internal CallbackDirectory easily extendable with new
types, templatize its callback registration and dispatching functions
to be able to replace its type switches and the internal union.

Change-Id: I3f636fef48973ac95253f1c1bd396550286e571e
Reviewed-by: Pierre Rossi <pierre.rossi@theqtcompany.com>

6 files changed, 315 insertions, 183 deletions

diff --git a/src/core/api/core_api.pro b/src/core/api/core_api.pro
index 829b59925..e0a6c2de4 100644
--- a/src/core/api/core_api.pro
+++ b/src/core/api/core_api.pro
@@ -26,6 +26,8 @@ INCLUDEPATH += $$QTWEBENGINE_ROOT/src/core \
 linux-g++*: QMAKE_CXXFLAGS += -Wno-unused-parameter
 
 HEADERS = \
+    qwebenginecallback.h \
+    qwebenginecallback_p.h \
     qtwebenginecoreglobal.h \
     qtwebenginecoreglobal_p.h \
 
diff --git a/src/core/api/qwebenginecallback.h b/src/core/api/qwebenginecallback.h
new file mode 100644
index 000000000..a88fa838c
--- /dev/null
+++ b/src/core/api/qwebenginecallback.h
@@ -0,0 +1,92 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtWebEngine module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWEBENGINECALLBACK_H
+#define QWEBENGINECALLBACK_H
+
+#include "qtwebenginecoreglobal.h"
+
+#include <QtCore/qcompilerdetection.h> // Needed for Q_DECL_OVERRIDE
+#include <QExplicitlySharedDataPointer>
+#include <QString>
+#include <QVariant>
+
+namespace QtWebEngineCore {
+class CallbackDirectory;
+}
+
+QT_BEGIN_NAMESPACE
+
+namespace QtWebEnginePrivate {
+
+template <typename T>
+class QWebEngineCallbackPrivateBase : public QSharedData {
+public:
+    QWebEngineCallbackPrivateBase() {}
+    virtual ~QWebEngineCallbackPrivateBase() {}
+    virtual void operator()(T) = 0;
+};
+
+template <typename T, typename F>
+class QWebEngineCallbackPrivate : public QWebEngineCallbackPrivateBase<T> {
+public:
+    QWebEngineCallbackPrivate(F callable)
+        : m_callable(callable)
+    {}
+    virtual void operator()(T value) Q_DECL_OVERRIDE { m_callable(value); }
+private:
+    F m_callable;
+};
+
+} // namespace QtWebEnginePrivate
+
+template <typename T>
+class QWebEngineCallback {
+public:
+    template <typename F>
+    QWebEngineCallback(F f)
+        : d(new QtWebEnginePrivate::QWebEngineCallbackPrivate<T, F>(f))
+    { }
+    QWebEngineCallback() { }
+    operator bool() const { return d; }
+private:
+    friend class QtWebEngineCore::CallbackDirectory;
+    QExplicitlySharedDataPointer<QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> > d;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWEBENGINECALLBACK_H
diff --git a/src/core/api/qwebenginecallback_p.h b/src/core/api/qwebenginecallback_p.h
new file mode 100644
index 000000000..9c798acbe
--- /dev/null
+++ b/src/core/api/qwebenginecallback_p.h
@@ -0,0 +1,213 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtWebEngine module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWEBENGINECALLBACK_P_H
+#define QWEBENGINECALLBACK_P_H
+
+#include "qtwebenginecoreglobal_p.h"
+#include "qwebenginecallback.h"
+
+#include <QHash>
+#include <QSharedData>
+#include <QString>
+#include <QVariant>
+#include <type_traits>
+
+#define FOR_EACH_TYPE(F) \
+    F(bool) \
+    F(int) \
+    F(const QString &) \
+    F(const QVariant &)
+
+namespace QtWebEngineCore {
+
+class CallbackDirectory {
+    template<typename T>
+    void invokeInternal(quint64 callbackId, T result);
+    template<typename T>
+    void invokeEmptyInternal(QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> *callback);
+
+public:
+    ~CallbackDirectory()
+    {
+        // "Cancel" pending callbacks by calling them with an invalid value.
+        // This guarantees that each callback is called exactly once.
+        for (CallbackSharedDataPointerBase * const sharedPtrBase: m_callbackMap) {
+            Q_ASSERT(sharedPtrBase);
+            sharedPtrBase->invokeEmpty();
+            delete sharedPtrBase;
+        }
+    }
+
+    template<typename T>
+    void registerCallback(quint64 callbackId, const QWebEngineCallback<T> &callback);
+
+    template<typename T>
+    void invokeEmpty(const QWebEngineCallback<T> &callback);
+
+#define DEFINE_INVOKE_FOR_TYPE(Type) \
+    void invoke(quint64 callbackId, Type result) { \
+        invokeInternal<Type>(callbackId, std::forward<Type>(result)); \
+    }
+    FOR_EACH_TYPE(DEFINE_INVOKE_FOR_TYPE)
+#undef DEFINE_INVOKE_FOR_TYPE
+
+private:
+    struct CallbackSharedDataPointerBase {
+        virtual ~CallbackSharedDataPointerBase() { }
+        virtual void invokeEmpty() = 0;
+        virtual void doRef() = 0;
+        virtual void doDeref() = 0;
+        virtual operator bool () const = 0;
+    };
+
+    template <typename T>
+    struct CallbackSharedDataPointer : public CallbackSharedDataPointerBase {
+        CallbackDirectory* parent;
+        QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> *callback;
+
+        ~CallbackSharedDataPointer() { doDeref(); }
+        CallbackSharedDataPointer() : parent(0), callback(0) { }
+        CallbackSharedDataPointer(const CallbackSharedDataPointer<T> &other)
+            : parent(other.parent), callback(other.callback) { doRef(); }
+        CallbackSharedDataPointer(CallbackDirectory *p, QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> *c)
+            : parent(p), callback(c) { Q_ASSERT(callback); doRef(); }
+
+        void invokeEmpty() override;
+        operator bool () const override { return callback; }
+
+    private:
+        void doRef() override;
+        void doDeref() override;
+    };
+
+    QHash<quint64, CallbackSharedDataPointerBase*> m_callbackMap;
+};
+
+template<typename T>
+inline
+void CallbackDirectory::registerCallback(quint64 callbackId, const QWebEngineCallback<T> &callback)
+{
+    if (!callback.d)
+        return;
+    m_callbackMap.insert(callbackId, new CallbackSharedDataPointer<T>(this, callback.d.data()));
+}
+
+template<typename T>
+inline
+void CallbackDirectory::invokeInternal(quint64 callbackId, T result)
+{
+    CallbackSharedDataPointerBase * const sharedPtrBase = m_callbackMap.take(callbackId);
+    if (!sharedPtrBase)
+        return;
+
+    auto ptr = static_cast<CallbackSharedDataPointer<T> *>(sharedPtrBase);
+    Q_ASSERT(ptr);
+    (*ptr->callback)(std::forward<T>(result));
+    delete ptr;
+}
+
+template<typename T>
+inline
+void CallbackDirectory::invokeEmptyInternal(QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> *callback)
+{
+    Q_ASSERT(callback);
+    using NoRefT = typename std::remove_reference<T>::type;
+    using NoConstNoRefT = typename std::remove_const<NoRefT>::type;
+    NoConstNoRefT t;
+    (*callback)(t);
+}
+
+template<>
+inline
+void CallbackDirectory::invokeEmptyInternal(QtWebEnginePrivate::QWebEngineCallbackPrivateBase<bool> *callback)
+{
+    Q_ASSERT(callback);
+    (*callback)(false);
+}
+
+template<>
+inline
+void CallbackDirectory::invokeEmptyInternal(QtWebEnginePrivate::QWebEngineCallbackPrivateBase<int> *callback)
+{
+    Q_ASSERT(callback);
+    (*callback)(0);
+}
+
+template<typename T>
+inline
+void CallbackDirectory::invokeEmpty(const QWebEngineCallback<T> &callback)
+{
+    if (!callback.d)
+        return;
+
+    invokeEmptyInternal(callback.d.data());
+}
+
+template <typename T>
+inline
+void CallbackDirectory::CallbackSharedDataPointer<T>::doRef()
+{
+    if (!callback)
+        return;
+
+    callback->ref.ref();
+}
+
+template <typename T>
+inline
+void CallbackDirectory::CallbackSharedDataPointer<T>::doDeref()
+{
+    if (!callback)
+        return;
+    if (!callback->ref.deref())
+        delete callback;
+}
+
+template <typename T>
+inline
+void CallbackDirectory::CallbackSharedDataPointer<T>::invokeEmpty()
+{
+    if (!callback)
+        return;
+
+    Q_ASSERT(parent);
+    parent->invokeEmptyInternal(callback);
+}
+
+} // namespace QtWebEngineCore
+
+#endif // QWEBENGINECALLBACK_P_H
diff --git a/src/webenginewidgets/api/qwebenginepage.cpp b/src/webenginewidgets/api/qwebenginepage.cpp
index bc0a97f97..bf5868925 100644
--- a/src/webenginewidgets/api/qwebenginepage.cpp
+++ b/src/webenginewidgets/api/qwebenginepage.cpp
@@ -79,106 +79,6 @@ static QWebEnginePage::WebWindowType toWindowType(WebContentsAdapterClient::Wind
     }
 }
 
-CallbackDirectory::~CallbackDirectory()
-{
-    // "Cancel" pending callbacks by calling them with an invalid value.
-    // This guarantees that each callback is called exactly once.
-    Q_FOREACH (const CallbackSharedDataPointer &sharedPtr, m_callbackMap) {
-        switch (sharedPtr.type) {
-        case CallbackSharedDataPointer::Variant:
-            (*sharedPtr.variantCallback)(QVariant());
-            break;
-        case CallbackSharedDataPointer::String:
-            (*sharedPtr.stringCallback)(QString());
-            break;
-        case CallbackSharedDataPointer::Bool:
-            (*sharedPtr.boolCallback)(false);
-            break;
-        default:
-            Q_UNREACHABLE();
-        }
-    }
-}
-
-void CallbackDirectory::registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<VariantCallback> &callback)
-{
-    m_callbackMap.insert(requestId, CallbackSharedDataPointer(callback.data()));
-}
-
-void CallbackDirectory::registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<StringCallback> &callback)
-{
-    m_callbackMap.insert(requestId, CallbackSharedDataPointer(callback.data()));
-}
-
-void CallbackDirectory::registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<BoolCallback> &callback)
-{
-    m_callbackMap.insert(requestId, CallbackSharedDataPointer(callback.data()));
-}
-
-void CallbackDirectory::invoke(quint64 requestId, const QVariant &result)
-{
-    CallbackSharedDataPointer sharedPtr = m_callbackMap.take(requestId);
-    if (sharedPtr) {
-        Q_ASSERT(sharedPtr.type == CallbackSharedDataPointer::Variant);
-        (*sharedPtr.variantCallback)(result);
-    }
-}
-
-void CallbackDirectory::invoke(quint64 requestId, const QString &result)
-{
-    CallbackSharedDataPointer sharedPtr = m_callbackMap.take(requestId);
-    if (sharedPtr) {
-        Q_ASSERT(sharedPtr.type == CallbackSharedDataPointer::String);
-        (*sharedPtr.stringCallback)(result);
-    }
-}
-
-void CallbackDirectory::invoke(quint64 requestId, bool result)
-{
-    CallbackSharedDataPointer sharedPtr = m_callbackMap.take(requestId);
-    if (sharedPtr) {
-        Q_ASSERT(sharedPtr.type == CallbackSharedDataPointer::Bool);
-        (*sharedPtr.boolCallback)(result);
-    }
-}
-
-void CallbackDirectory::CallbackSharedDataPointer::doRef()
-{
-    switch (type) {
-    case None:
-        break;
-    case Variant:
-        variantCallback->ref.ref();
-        break;
-    case String:
-        stringCallback->ref.ref();
-        break;
-    case Bool:
-        boolCallback->ref.ref();
-        break;
-    }
-}
-
-void CallbackDirectory::CallbackSharedDataPointer::doDeref()
-{
-    switch (type) {
-    case None:
-        break;
-    case Variant:
-        if (!variantCallback->ref.deref())
-            delete variantCallback;
-        break;
-    case String:
-        if (!stringCallback->ref.deref())
-            delete stringCallback;
-        break;
-    case Bool:
-        if (!boolCallback->ref.deref())
-            delete boolCallback;
-        break;
-    }
-}
-
 QWebEnginePagePrivate::QWebEnginePagePrivate(QWebEngineProfile *_profile)
     : adapter(new WebContentsAdapter)
     , history(new QWebEngineHistory(new QWebEngineHistoryPrivate(this)))
@@ -814,12 +714,10 @@ void QWebEnginePage::findText(const QString &subString, FindFlags options, const
     Q_D(QWebEnginePage);
     if (subString.isEmpty()) {
         d->adapter->stopFinding();
-        if (resultCallback.d)
-            (*resultCallback.d)(false);
+        d->m_callbacks.invokeEmpty(resultCallback);
     } else {
         quint64 requestId = d->adapter->findText(subString, options & FindCaseSensitively, options & FindBackward);
-        if (resultCallback.d)
-            d->m_callbacks.registerCallback(requestId, resultCallback.d);
+        d->m_callbacks.registerCallback(requestId, resultCallback);
     }
 }
 
@@ -1087,14 +985,14 @@ void QWebEnginePage::toHtml(const QWebEngineCallback<const QString &> &resultCal
 {
     Q_D(const QWebEnginePage);
     quint64 requestId = d->adapter->fetchDocumentMarkup();
-    d->m_callbacks.registerCallback(requestId, resultCallback.d);
+    d->m_callbacks.registerCallback(requestId, resultCallback);
 }
 
 void QWebEnginePage::toPlainText(const QWebEngineCallback<const QString &> &resultCallback) const
 {
     Q_D(const QWebEnginePage);
     quint64 requestId = d->adapter->fetchDocumentInnerText();
-    d->m_callbacks.registerCallback(requestId, resultCallback.d);
+    d->m_callbacks.registerCallback(requestId, resultCallback);
 }
 
 void QWebEnginePage::setHtml(const QString &html, const QUrl &baseUrl)
@@ -1161,7 +1059,7 @@ void QWebEnginePage::runJavaScript(const QString& scriptSource, const QWebEngine
 {
     Q_D(QWebEnginePage);
     quint64 requestId = d->adapter->runJavaScriptCallbackResult(scriptSource);
-    d->m_callbacks.registerCallback(requestId, resultCallback.d);
+    d->m_callbacks.registerCallback(requestId, resultCallback);
 }
 
 /*!
diff --git a/src/webenginewidgets/api/qwebenginepage.h b/src/webenginewidgets/api/qwebenginepage.h
index 4281a70a0..16b33a196 100644
--- a/src/webenginewidgets/api/qwebenginepage.h
+++ b/src/webenginewidgets/api/qwebenginepage.h
@@ -39,6 +39,7 @@
 
 #include <QtWebEngineWidgets/qtwebenginewidgetsglobal.h>
 #include <QtWebEngineWidgets/qwebenginecertificateerror.h>
+#include <QtWebEngineCore/qwebenginecallback.h>
 
 #include <QtCore/qobject.h>
 #include <QtCore/qurl.h>
@@ -56,37 +57,6 @@ class QWebEngineProfile;
 class QWebEngineScriptCollection;
 class QWebEngineSettings;
 
-namespace QtWebEnginePrivate {
-
-template <typename T>
-class QWebEngineCallbackPrivateBase : public QSharedData {
-public:
-    virtual ~QWebEngineCallbackPrivateBase() {}
-    virtual void operator()(T) = 0;
-};
-
-template <typename T, typename F>
-class QWebEngineCallbackPrivate : public QWebEngineCallbackPrivateBase<T> {
-public:
-    QWebEngineCallbackPrivate(F callable) : m_callable(callable) {}
-    virtual void operator()(T value) Q_DECL_OVERRIDE { m_callable(value); }
-private:
-    F m_callable;
-};
-
-} // namespace QtWebEnginePrivate
-
-template <typename T>
-class QWebEngineCallback {
-public:
-    template <typename F>
-    QWebEngineCallback(F f) : d(new QtWebEnginePrivate::QWebEngineCallbackPrivate<T, F>(f)) { }
-    QWebEngineCallback() { }
-private:
-    QExplicitlySharedDataPointer<QtWebEnginePrivate::QWebEngineCallbackPrivateBase<T> > d;
-    friend class QWebEnginePage;
-};
-
 class QWEBENGINEWIDGETS_EXPORT QWebEnginePage : public QObject {
     Q_OBJECT
     Q_PROPERTY(QString selectedText READ selectedText)
diff --git a/src/webenginewidgets/api/qwebenginepage_p.h b/src/webenginewidgets/api/qwebenginepage_p.h
index 62ca16415..a5ede1a8e 100644
--- a/src/webenginewidgets/api/qwebenginepage_p.h
+++ b/src/webenginewidgets/api/qwebenginepage_p.h
@@ -39,10 +39,10 @@
 
 #include "qwebenginepage.h"
 
+#include "qwebenginecallback_p.h"
 #include "qwebenginescriptcollection.h"
 #include "web_contents_adapter_client.h"
 #include <QtCore/qcompilerdetection.h>
-#include <QSharedData>
 
 namespace QtWebEngineCore {
 class RenderWidgetHostViewQtDelegate;
@@ -56,49 +56,6 @@ class QWebEngineProfile;
 class QWebEngineSettings;
 class QWebEngineView;
 
-class CallbackDirectory {
-public:
-    typedef QtWebEnginePrivate::QWebEngineCallbackPrivateBase<const QVariant&> VariantCallback;
-    typedef QtWebEnginePrivate::QWebEngineCallbackPrivateBase<const QString&> StringCallback;
-    typedef QtWebEnginePrivate::QWebEngineCallbackPrivateBase<bool> BoolCallback;
-
-    ~CallbackDirectory();
-    void registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<VariantCallback> &callback);
-    void registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<StringCallback> &callback);
-    void registerCallback(quint64 requestId, const QExplicitlySharedDataPointer<BoolCallback> &callback);
-    void invoke(quint64 requestId, const QVariant &result);
-    void invoke(quint64 requestId, const QString &result);
-    void invoke(quint64 requestId, bool result);
-
-private:
-    struct CallbackSharedDataPointer {
-        enum {
-            None,
-            Variant,
-            String,
-            Bool
-        } type;
-        union {
-            VariantCallback *variantCallback;
-            StringCallback *stringCallback;
-            BoolCallback *boolCallback;
-        };
-        CallbackSharedDataPointer() : type(None) { }
-        CallbackSharedDataPointer(VariantCallback *callback) : type(Variant), variantCallback(callback) { callback->ref.ref(); }
-        CallbackSharedDataPointer(StringCallback *callback) : type(String), stringCallback(callback) { callback->ref.ref(); }
-        CallbackSharedDataPointer(BoolCallback *callback) : type(Bool), boolCallback(callback) { callback->ref.ref(); }
-        CallbackSharedDataPointer(const CallbackSharedDataPointer &other) : type(other.type), variantCallback(other.variantCallback) { doRef(); }
-        ~CallbackSharedDataPointer() { doDeref(); }
-        operator bool () const { return type != None; }
-
-    private:
-        void doRef();
-        void doDeref();
-    };
-
-    QHash<quint64, CallbackSharedDataPointer> m_callbackMap;
-};
-
 class QWebEnginePagePrivate : public QtWebEngineCore::WebContentsAdapterClient
 {
 public:
@@ -171,7 +128,7 @@ public:
     bool isLoading;
     QWebEngineScriptCollection scriptCollection;
 
-    mutable CallbackDirectory m_callbacks;
+    mutable QtWebEngineCore::CallbackDirectory m_callbacks;
     mutable QAction *actions[QWebEnginePage::WebActionCount];
 };