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/****************************************************************************
**
** Copyright (C) 2019 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 wasm.html
\title Qt for WebAssembly
\brief Runs Qt applications in a secure sandbox in the browser
\ingroup supportedplatform
WebAssembly is a binary format that allows sand-boxed executable code
in web pages. This format is nearly as fast as native machine code, and
is now supported by all major web browsers.
Qt for WebAssembly is a \l {Qt Platform Abstraction}{platform plugin} that
lets you build Qt applications, which can be integrated into your web pages.
It doesn't require any client-side installations and reduces the server-side
resource usage.
\section1 Getting Started with Qt for WebAssembly
\section2 Install Emscripten
\l{emscripten} is a toolchain for compiling to asm.js and Webassembly.
It lets you run Qt on the web at near-native speed without plugins.
Refer to the \l{http://kripken.github.io/emscripten-site/docs/getting_started/index.html}{emscripten documentation} for the installation procedure.
After installation, you should have emscripten in your path.
Check this with the following command:
\badcode
em++ --version
\endcode
\section2 Build Qt from the sources
Download the Qt 5.12 sources and build Qt from source. Specify that
we are cross-compiling for \c wasm using \c emscripten:
\badcode
$ ~/Qt/5.12.0/Src/configure -xplatform wasm-emscripten -nomake examples -prefix $PWD/qtbase
$ make module-qtbase module-qtdeclarative [other modules]
\endcode
The Qt build is a static build, and does not support threads.
\section2 Build your application
\badcode
$ /path/to/qt-wasm/qtbase/bin/qmake
$ make
\endcode
This generates the following files:
\table
\header
\li Generated file
\li Brief Description
\row
\li app.html
\li HTML container
\row
\li qtloader.js \li JS API for loading Qt apps
\row
\li app.js
\li JS API for loading Qt apps
\row
\li app.wasm
\li emscripten app binary
\endtable
When deploying the app, the compression is typically handled on
the server side. We recommend to compress the wasm binaries because
this typically reduces the size of the binary by 50 %.
\sa {WebAssembly Resource site},{Getting Started with Qt for WebAssembly},
{Remote UIs with WegGL and WebAssemblhy}
\section1 Some examples
\list
\li \l {http://example.qt.io/qt-webassembly/opengl/hellowindow/hellowindow.html}
{An example displaying a Qt logo using OpenGL calls}
\li \l {http://example.qt.io/qt-webassembly/SensorTagDemo/SensorTagDemo.html}
{An industry automation use case}
\li \l {http://example.qt.io/qt-webassembly/quickcontrols2/gallery/gallery.html}
{A gallery of available controls in Qt Quick Controls}
\li \l {http://example.qt.io/qt-webassembly/widgets/richtext/textedit/textedit.html}
{A simple text editor, written with Qt Widgets}
\endlist
\section1 Limitations
The most important limitation is that the Qt build is static,
and does not support threads.
For further info, refer to \l { https://wiki.qt.io/Qt_for_WebAssembly#Known_issues_and_platform_notes}{Known_issues_and_platform_notes}.
\section1 External resources
\list
\li \l {Qt for WebAssembly Technology Preview}
\li \l {Qt and WebAssembly}
\li \l {Qt for WebAssembly wiki}
\li \l {Getting Started with Qt for WebAssembly}
\li \l {Remote UIs with WebGL and WebAssembly}
\li \l {WebAssembly Resource site}
\endlist
\section1 Licenses
Qt for WebAssembly is available under commercial licenses from \l{The Qt Company}.
In addition, it is available under the \l{GNU General Public License, version 3}.
See \l{Qt Licensing} for further details.
*/
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