createWindow QML API for QQuickWebEngineView

This implements adoptNewWindow for QQuickWebEngineView.
The API is only intended to be used through QML to avoid delegating
the QQuickWebEngineViewHandle ownership through a signal parameter.

Another limitation of the implementation is currently to fail the
handle adoption unless it is done synchronously within the
adoptNewWindow call. To support this we would need to delay the call
to WebContentsAdapter::initialize which will leave the adapter
without a client when returning to the event loop and would require
putting null checks everywhere it is used.
So I would prefer to keep the API limited and avoid potential crashes.
If we want to support asynchronous Loader elements or QML files
fetched from the network in the future, the API should be able to
scale to the task once we've adjusted the implementation.

This also adds basic tabs support in the quicknanobrowser example.
The url property is now set imperatively to avoid overwriting the
adopted WebContentsAdapter's loading URL.

Change-Id: Iba5c5dc3ffa21045f356be131ca15c01b9aee7c8
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>

5 files changed, 168 insertions, 21 deletions

diff --git a/examples/quick/quicknanobrowser/quickwindow.cpp b/examples/quick/quicknanobrowser/quickwindow.cpp
index 3b89aa205..df93cd218 100644
--- a/examples/quick/quicknanobrowser/quickwindow.cpp
+++ b/examples/quick/quicknanobrowser/quickwindow.cpp
@@ -54,7 +54,6 @@ class Utils : public QObject {
 public:
     Utils(QObject* parent = 0) : QObject(parent) { }
     Q_INVOKABLE static QUrl fromUserInput(const QString& userInput) { return urlFromUserInput(userInput); }
-    Q_INVOKABLE static QUrl initialUrl() { return startupUrl(); }
 };
 
 #include "quickwindow.moc"
@@ -63,4 +62,5 @@ ApplicationEngine::ApplicationEngine()
 {
     rootContext()->setContextProperty("utils", new Utils(this));
     load(QUrl("qrc:/quickwindow.qml"));
+    QMetaObject::invokeMethod(rootObjects().first(), "load", Q_ARG(QVariant, startupUrl()));
 }
diff --git a/examples/quick/quicknanobrowser/quickwindow.qml b/examples/quick/quicknanobrowser/quickwindow.qml
index 3d3dd9470..7ef33c14e 100644
--- a/examples/quick/quicknanobrowser/quickwindow.qml
+++ b/examples/quick/quicknanobrowser/quickwindow.qml
@@ -40,26 +40,46 @@
 
 import QtQuick 2.0
 import QtWebEngine 1.0
+import QtWebEngine.experimental 1.0
 import QtQuick.Controls 1.0
 import QtQuick.Controls.Styles 1.0
 import QtQuick.Layouts 1.0
 
 ApplicationWindow {
     id: browserWindow
+    function load(url) { tabs.currentView.url = url }
+    function adoptHandle(viewHandle) { tabs.currentView.adoptHandle(viewHandle) }
+
     height: 600
     width: 800
     visible: true
-    title: webEngineView.title
+    title: tabs.currentView && tabs.currentView.title
 
-    // Focus and select text in URL bar
     Action {
         id: focus
-        shortcut: "Ctrl+L" // How to have Cmd + L on Mac ?
+        shortcut: "Ctrl+L"
         onTriggered: {
             addressBar.forceActiveFocus();
             addressBar.selectAll();
         }
     }
+    Action {
+        shortcut: "Ctrl+T"
+        onTriggered: {
+            tabs.createEmptyTab()
+            addressBar.forceActiveFocus();
+            addressBar.selectAll();
+        }
+    }
+    Action {
+        shortcut: "Ctrl+W"
+        onTriggered: {
+            if (tabs.count == 1)
+                browserWindow.close()
+            else
+                tabs.removeTab(tabs.currentIndex)
+        }
+    }
 
     toolBar: ToolBar {
         id: navigationBar
@@ -68,19 +88,19 @@ ApplicationWindow {
                 ToolButton {
                     id: backButton
                     iconSource: "icons/go-previous.png"
-                    onClicked: webEngineView.goBack()
-                    enabled: webEngineView.canGoBack
+                    onClicked: tabs.currentView.goBack()
+                    enabled: tabs.currentView && tabs.currentView.canGoBack
                 }
                 ToolButton {
                     id: forwardButton
                     iconSource: "icons/go-next.png"
-                    onClicked: webEngineView.goForward()
-                    enabled: webEngineView.canGoForward
+                    onClicked: tabs.currentView.goForward()
+                    enabled: tabs.currentView && tabs.currentView.canGoForward
                 }
                 ToolButton {
                     id: reloadButton
-                    iconSource: webEngineView.loading ? "icons/process-stop.png" : "icons/view-refresh.png"
-                    onClicked: webEngineView.reload()
+                    iconSource: tabs.currentView && tabs.currentView.loading ? "icons/process-stop.png" : "icons/view-refresh.png"
+                    onClicked: tabs.currentView.reload()
                 }
                 TextField {
                     id: addressBar
@@ -90,6 +110,7 @@ ApplicationWindow {
                         z: 2
                         id: faviconImage
                         width: 16; height: 16
+                        source: tabs.currentView && tabs.currentView.icon
                     }
                     style: TextFieldStyle {
                         padding {
@@ -98,7 +119,8 @@ ApplicationWindow {
                     }
                     focus: true
                     Layout.fillWidth: true
-                    onAccepted: webEngineView.url = utils.fromUserInput(text)
+                    text: tabs.currentView && tabs.currentView.url
+                    onAccepted: tabs.currentView.url = utils.fromUserInput(text)
                 }
             }
             ProgressBar {
@@ -117,16 +139,46 @@ ApplicationWindow {
                 z: -2;
                 minimumValue: 0
                 maximumValue: 100
+                value: tabs.currentView && tabs.currentView.loadProgress
             }
     }
-    WebEngineView {
-        id: webEngineView
-        focus: true
+
+    TabView {
+        id: tabs
+        property Item currentView: currentIndex < count ? getTab(currentIndex).item : null
+        function createEmptyTab() {
+            var tab = addTab("", tabComponent)
+            // We must do this first to make sure that tab.active gets set so that tab.item gets instantiated immediately.
+            tabs.currentIndex = tabs.count - 1
+            tab.title = Qt.binding(function() { return tab.item.title })
+            return tab
+        }
+
         anchors.fill: parent
-        url: utils.initialUrl()
+        Component.onCompleted: createEmptyTab()
+
+        Component {
+            id: tabComponent
+            WebEngineView {
+                function adoptHandle(viewHandle) { experimental.adoptHandle(viewHandle) }
+
+                focus: true
 
-        onUrlChanged: addressBar.text = url
-        onIconChanged: faviconImage.source = icon
-        onLoadProgressChanged: progressBar.value = loadProgress
+                experimental {
+                    onCreateWindow: {
+                        if (newViewDisposition == "popup")
+                            print("Warning: Ignored a popup window.")
+                        else if (newViewDisposition == "tab") {
+                            var tab = tabs.createEmptyTab()
+                            tab.item.adoptHandle(newViewHandle)
+                        } else {
+                            var component = Qt.createComponent("quickwindow.qml")
+                            var window = component.createObject()
+                            window.adoptHandle(newViewHandle)
+                        }
+                    }
+                }
+            }
+        }
     }
 }
diff --git a/src/webengine/api/qquickwebengineview.cpp b/src/webengine/api/qquickwebengineview.cpp
index e9375148e..d159ed8fc 100644
--- a/src/webengine/api/qquickwebengineview.cpp
+++ b/src/webengine/api/qquickwebengineview.cpp
@@ -47,6 +47,7 @@
 
 #include <QScreen>
 #include <QUrl>
+#include <QQmlEngine>
 
 QT_BEGIN_NAMESPACE
 
@@ -158,9 +159,48 @@ void QQuickWebEngineViewPrivate::focusContainer()
 
 void QQuickWebEngineViewPrivate::adoptNewWindow(WebContentsAdapter *newWebContents, WindowOpenDisposition disposition, const QRect &)
 {
-    Q_UNUSED(newWebContents);
-    Q_UNUSED(disposition);
-    Q_UNREACHABLE();
+    Q_Q(QQuickWebEngineView);
+    QQmlEngine *engine = QtQml::qmlEngine(q);
+    // This is currently only supported for QML instantiated WebEngineViews.
+    // We could emit a QObject* and set JavaScriptOwnership explicitly on it
+    // but this would make the signal cumbersome to use in C++ where one, and
+    // only one, of the connected slots would have to destroy the given handle.
+    // A virtual method instead of a signal would work better in this case.
+    if (!engine)
+        return;
+    static const QMetaMethod createWindowSignal = QMetaMethod::fromSignal(&QQuickWebEngineViewExperimental::createWindow);
+    if (!e->isSignalConnected(createWindowSignal))
+        return;
+
+    QQuickWebEngineViewHandle *handle = new QQuickWebEngineViewHandle;
+    // This increases the ref-count of newWebContents and will tell Chromium
+    // to start loading it and possibly return it to its parent page window.open().
+    handle->adapter = newWebContents;
+    // Clearly mark our wrapper as owned by JavaScript, we then depend on it
+    // being adopted or else eventually cleaned up by the GC.
+    QJSValue jsHandle = engine->newQObject(handle);
+
+    QString dispositionString;
+    switch (disposition) {
+    case WebContentsAdapterClient::NewForegroundTabDisposition:
+    case WebContentsAdapterClient::NewBackgroundTabDisposition:
+        dispositionString = QStringLiteral("tab");
+        break;
+    case WebContentsAdapterClient::NewPopupDisposition:
+        dispositionString = QStringLiteral("popup");
+        break;
+    case WebContentsAdapterClient::NewWindowDisposition:
+        dispositionString = QStringLiteral("window");
+        break;
+    default:
+        Q_UNREACHABLE();
+    }
+
+    emit e->createWindow(jsHandle, dispositionString);
+
+    // We currently require the adoption to happen within the signal handler to avoid having
+    // to support a null WebContentsAdapterClient for too long after having returned.
+    handle->adapter.reset();
 }
 
 void QQuickWebEngineViewPrivate::close()
@@ -285,6 +325,14 @@ void QQuickWebEngineView::geometryChanged(const QRectF &newGeometry, const QRect
     }
 }
 
+QQuickWebEngineViewHandle::QQuickWebEngineViewHandle()
+{
+}
+
+QQuickWebEngineViewHandle::~QQuickWebEngineViewHandle()
+{
+}
+
 QQuickWebEngineViewExperimental::QQuickWebEngineViewExperimental(QQuickWebEngineViewPrivate *viewPrivate)
     : q_ptr(0)
     , d_ptr(viewPrivate)
@@ -320,4 +368,34 @@ void QQuickWebEngineViewport::setDevicePixelRatio(qreal devicePixelRatio)
     Q_EMIT devicePixelRatioChanged();
 }
 
+void QQuickWebEngineViewExperimental::adoptHandle(QQuickWebEngineViewHandle *viewHandle)
+{
+    if (!viewHandle || !viewHandle->adapter) {
+        qWarning("Trying to adopt an empty handle, it was either already adopted or was invalidated."
+            "\nYou must do the adoption synchronously within the createWindow signal handler."
+            " If the handle hasn't been adopted before returning, it will be invalidated.");
+        return;
+    }
+
+    Q_Q(QQuickWebEngineView);
+    Q_D(QQuickWebEngineView);
+
+    // This throws away the WebContentsAdapter that has been used until now.
+    // All its states, particularly the loading URL, are replaced by the adopted WebContentsAdapter.
+    d->adapter = viewHandle->adapter;
+    viewHandle->adapter.reset();
+
+    d->adapter->initialize(d);
+
+    // Emit signals for values that might be different from the previous WebContentsAdapter.
+    emit q->titleChanged();
+    emit q->urlChanged();
+    emit q->iconChanged();
+    emit q->loadingStateChanged();
+    emit q->loadProgressChanged();
+}
+
 QT_END_NAMESPACE
+
+#include "moc_qquickwebengineview_p.cpp"
+#include "moc_qquickwebengineview_p_p.cpp"
diff --git a/src/webengine/api/qquickwebengineview_p_p.h b/src/webengine/api/qquickwebengineview_p_p.h
index b356b8881..0af1dcb45 100644
--- a/src/webengine/api/qquickwebengineview_p_p.h
+++ b/src/webengine/api/qquickwebengineview_p_p.h
@@ -71,11 +71,27 @@ private:
     Q_DECLARE_PRIVATE(QQuickWebEngineView)
 };
 
+class Q_WEBENGINE_PRIVATE_EXPORT QQuickWebEngineViewHandle : public QObject {
+    Q_OBJECT
+public:
+    QQuickWebEngineViewHandle();
+    ~QQuickWebEngineViewHandle();
+
+private:
+    QExplicitlySharedDataPointer<WebContentsAdapter> adapter;
+    friend class QQuickWebEngineViewExperimental;
+    friend class QQuickWebEngineViewPrivate;
+};
+
 class Q_WEBENGINE_PRIVATE_EXPORT QQuickWebEngineViewExperimental : public QObject {
     Q_OBJECT
     Q_PROPERTY(QQuickWebEngineViewport *viewport READ viewport)
 public:
     QQuickWebEngineViewport *viewport() const;
+    Q_INVOKABLE void adoptHandle(QQuickWebEngineViewHandle *viewHandle);
+
+Q_SIGNALS:
+    void createWindow(const QJSValue &newViewHandle, const QString &newViewDisposition);
 
 private:
     QQuickWebEngineViewExperimental(QQuickWebEngineViewPrivate* viewPrivate);
diff --git a/src/webengine/render_widget_host_view_qt_delegate_quick.h b/src/webengine/render_widget_host_view_qt_delegate_quick.h
index e8e073c24..b31a9c873 100644
--- a/src/webengine/render_widget_host_view_qt_delegate_quick.h
+++ b/src/webengine/render_widget_host_view_qt_delegate_quick.h
@@ -68,6 +68,7 @@ public:
     {
         QQuickWebEngineViewPrivate *viewPrivate = static_cast<QQuickWebEngineViewPrivate *>(container);
         this->setParentItem(viewPrivate->q_func());
+        this->setSize(viewPrivate->q_func()->boundingRect().size());
     }
 
     virtual void initAsPopup(const QRect& rect) Q_DECL_OVERRIDE