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/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** 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 https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qtwebengine-overview.html
\title Qt WebEngine Overview
The Qt WebEngine module provides a web browser engine that makes it easy to embed content from
the World Wide Web into your Qt application on platforms that do not have a native web engine.
The web engine is not intended to function as a \e {Web Runtime}; to display web content in a
QML application by using APIs native to the platform, use the \l{Qt WebView} module, instead.
Qt WebEngine provides C++ classes and QML types for rendering HTML, XHTML, and SVG documents,
styled using Cascading Style Sheets (CSS) and scripted with JavaScript. HTML documents can be
made fully editable by the user through the use of the \c{contenteditable} attribute on HTML
elements.
Qt WebEngine supercedes the \l{http://doc.qt.io/archives/qt-5.3/qtwebkit-index.html}{Qt WebKit}
module, which is based on the
WebKit project, but has not been actively synchronized with the upstream WebKit code since
Qt 5.2 and has been deprecated in Qt 5.5. For tips on how to change a Qt WebKit widgets
application to use Qt WebEngine widgets, see \l{Porting from Qt WebKit to Qt WebEngine}. For new
applications, we recommend using Qt Quick and the WebEngineView QML type.
For more information about the requirements for building Qt WebEngine from source on the
supported platforms and for other platform-specific information, see
\l{Qt WebEngine Platform Notes}.
The \l {Qt WebChannel} module can be used to create a bi-directional communication channel
between QObject objects on the C++ side and JavaScript on the QML side.
\section1 Qt WebEngine Architecture
\image qtwebengine-architecture.png
The functionality in Qt WebEngine is divided into the following modules:
\list
\li \l{Qt WebEngine Widgets} for creating widget-based web applications
\li \l{Qt WebEngine} for creating Qt Quick based web applications
\li \l{Qt WebEngine Core} for interacting with Chromium
\endlist
Page rendering and JavaScript execution are separated from the GUI process into the Qt WebEngine
Process. It is a library that must be shipped with the application if the Qt libraries are
bundled into the application.
\section2 Qt WebEngine Widgets
\image qtwebenginewidgets-model.png
A \e {web engine view} is the main widget component of the Qt WebEngine module. It can be used
in various applications to load web content. Within a view, a \e {web engine page} holds a main
frame that is responsible for web content, the \e history of navigated links, and \e actions.
The view and page are quite similar, as they provide a set of common functions.
All pages belong to a \e {web engine profile} that contains shared \e settings, \e scripts, and
\e cookies. Profiles can be used to isolate pages from each other. A typical use case is a
dedicated profile for a \e {private browsing} mode, where no information is permanently saved.
\section2 Qt WebEngine
\image qtwebengine-model.png
The Qt WebEngine QML implementation contains the same elements as the C++ implementation,
except that there is no separately accessible web engine page. The supported page functionality
is integrated into the web engine view.
\section2 Qt WebEngine Core
The Qt WebEngine core is based on the \l {Chromium Project}. Chromium provides its own network
and painting engines and is developed tightly together with its dependent modules, and
therefore Qt WebEngine provides better and more reliable support for the latest HTML5
specification than Qt WebKit. However, Qt WebEngine is thus heavier than Qt WebKit and does
not provide direct access to the network stack and the HTML document through C++ APIs.
Please note that Qt WebEngine is based on Chromium, but does not contain or use any services
or add-ons that might be part of the Chrome browser that is built and delivered by Google.
You can find more detailed information about the differences between Chromium and Chrome in this
\l{https://chromium.googlesource.com/chromium/src/+/master/docs/chromium_browser_vs_google_chrome.md}{overview}
that is part of the documentation in the \l {Chromium Project} upstream source tree.
This version of Qt WebEngine is based on Chromium snapshot version 45.0.2554.101, with
additional security fixes from the 46, 47 and 48 branches of the \l {Chromium Project}.
\section2 Qt WebEngine Process
The Qt WebEngine Process renders web pages and executes JavaScript.
Chromium is tightly integrated to the \l{Qt Quick Scene Graph}{Qt Quick scene graph}, which is
based on OpenGL ES 2.0 or OpenGL 2.0 for its rendering. This provides you with one-pass
compositing of web content and all the Qt Quick UI. The integration to Chromium is transparent
to developers, who just work with Qt and JavaScript.
The document object model (DOM) of a page is constructed when the document is ready, typically
when the page is completely loaded. Therefore, executing scripts as soon as a document is
created is not suitable for DOM operations, where one has to wait until the DOM is ready.
In addition, an injected script shares the same \e world as the other scripts executed on the
page, which might lead to conflicts. To avoid this, the QWebEngineScript class and the
WebEngineScript QML type provide implementations of the Chromium API for
\e{Content Script Extensions}. They specify the
script to run, the injection point, and the world where the script is run. This enables
accessing the DOM to manipulate it within a world.
\note Chromium extensions, such as \c @include, \c @match, and \c @exclude, are not supported.
Because the render process is separated from the GUI process, they should ideally share an
OpenGL context to enable one process to access the resources uploaded by the other, such as
images or textures. However, some inter-process communication is needed for safety and
reliability, because it enables restarting a crashed process.
\section1 Embedding Web Content into Widget Based Applications
Use the QWebEngineView class to display web pages in the simplest way. Because it is a widget,
you can embed QWebEngineView into your forms and use its convenience functions to download and
display web sites.
\code
QWebEngineView *view = new QWebEngineView(parent);
view->load(QUrl("http://www.qt.io/"));
view->show();
\endcode
An instance of QWebEngineView has one QWebEnginePage. QWebEnginePage can have a
QWebEngineHistory that provides access to the page's navigation history and several QAction
objects that apply actions on the web page. In addition, a QWebEnginePage has the ability to
run JavaScript code in the context of the page's main frame and to enable customization of
handlers for specific events like showing custom authentication dialogs.
Each QWebEnginePage belongs to a QWebEngineProfile that can have a QWebEngineSettings
for specifying page settings, a QWebEngineScriptCollection for running scripts on the page, and
a QWebEngineCookieStore for accessing the HTTP cookies of Chromium. A QWebEnginePage can also
directly point to a script collection.
\section1 Embedding Web Content into Qt Quick Applications
The WebEngineView QML type allows Qt Quick applications to render regions of dynamic web
content. A \e{WebEngineView} type may share the screen with other QML types or encompass the
full screen as specified within the Qt Quick application.
To make sure that OpenGL context can be shared between the GUI and render processes, the web
engine must be initialized by using \l QtWebEngine::initialize in the application main source
file, as illustrated by the following code snippet:
\quotefromfile webengine/minimal/main.cpp
\skipto main
\printuntil }
An application can load pages into the WebEngineView, using either an URL or HTML string, and
navigate within session history. By default, links to different pages load within the same
WebEngineView object, but web sites may request them to be opened as a new tab, window, or
dialog.
The following sample QML application loads a web page using the \l{WebEngineView::}{url}
property:
\quotefromfile webengine/minimal/main.qml
\skipto import
\printuntil /^\}/
\section1 Managing Certificates
Qt WebEngine uses its own network stack, and therefore QSslConfiguration is not used to
open SSL connections. Instead, Qt WebEngine uses the root CA certificates from the operating
system to validate the peer's certificate.
The \l{WebEngineCertificateError::error} and \l{QWebEngineCertificateError::Error} enumerations
provide information about the types of certificate errors that might occur. The errors can be
handled by using the WebEngineView::certificateError QML method or by reimplementing the
QWebEnginePage::certificateError function.
\section1 Proxy Support
If QNetworkProxy::applicationProxy is set, it will also be used for Qt WebEngine. Otherwise,
Qt WebEngine automatically picks up the proxy configuration from OS X and Windows. On Linux,
it acknowledges settings from KDE and Gnome.
If a proxy requires authentication, QWebEnginePage::proxyAuthenticationRequired is emitted.
For Qt Quick, a dialog is shown.
\section1 Using WebEngine Core
Qt WebEngine Core provides an API shared by Qt WebEngine and Qt WebEngine Widgets for handling
URL requests issued for the networking stack of Chromium and for accessing its HTTP cookies.
Implementing the QWebEngineUrlRequestInterceptor interface and installing the interceptor on a
profile enables intercepting, blocking, and modifying URL requests (QWebEngineUrlRequestInfo)
before they reach the networking stack of Chromium.
A QWebEngineUrlSchemeHandler can be registered for a profile to add support for custom URL
schemes. Requests for the scheme are then issued to QWebEngineUrlSchemeHandler::requestStarted()
as QWebEngineUrlRequestJob objects.
The QWebEngineCookieStore class provides functions for accessing HTTP cookies of Chromium.
The functions can be used to synchronize cookies with QNetworkAccessManager, as well as to set,
delete, and intercept cookies during navigation.
\section1 Deploying Qt WebEngine Applications
Qt WebEngine takes advantage of the multi process model that the Chromium project offers.
The multi process model requires the QtWebEngineProcess executable to be deployed alongside your application.
To do this, we recommend the use of Qt's cross-platform deployment tools.
Alternatively, if you are carrying out manual deployment, you will find the QtWebEngineProcess executable in the
libexec directory of your Qt installation.
On Windows, QtWebEngineProcess.exe is located in the bin directory of your Qt application.
For more information on deploying Qt applications, please see \l {Deploying Qt Applications}.
\section1 License Information
Qt WebEngine module is a snapshot of the integration of Chromium into Qt.
Qt Commercial Edition licensees that wish to distribute applications that
use the Qt WebEngine module need to be aware of their obligations under the
GNU Library General Public License (LGPLv2).
Developers using the Open Source Edition can choose to redistribute
the module under the GNU LGPLv3 or GPLv2 and up.
\legalese
Chromium is licensed under the following license:
Copyright (c) 2013 The Chromium Authors. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
* Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\endlegalese
*/
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