Qt for WebAssembly

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Revision as of 10:10, 23 April 2018 by Eskil (talk | contribs)
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Qt for WebAssembly makes it possible to build Qt applications as WebAssembly modules in order to target Web browsers.

Qt for WebAssembly is currently in development. A tech preview release is scheduled for release with Qt 5.11.

This Wiki page is also a work in progress, please see the development tracking bug for more information: https://bugreports.qt.io/browse/QTBUG-63917

Getting the code

qtbase branch: wip/webassembly ( git clone -b wip/webassembly https://code.qt.io/qt/qtbase.git )

qtdeclarative branch: wip/webassembly ( git clone -b wip/webassembly https://code.qt.io/qt/qtdeclarative.git )

Building Qt

Requirements: Emscripten (known-good version: 1.37.33)

Supported host dev platforms: linux, macOS (Windows is not currently supported)

./configure -xplatform emscripten -confirm-license -opensource -developer-build -release -static -no-thread -nomake tests -nomake examples  -no-dbus -no-headersclean -no-feature-networkinterface  -system-libpng -no-ssl -no-warnings-are-errors --release

make

Building and running applications

/path/to/qmake && make

Start a web server (e.g. "python -m SimpleHTTPServer"), open e.g. localhost:8000/appname.html in a web browser. We test on Chrome, Firefox, and Safari (all desktop). Firefox (nightly) currently has the most performant wasm compiler, and is recommended for dev work.

You can also use:

/path/to/emscripten/emrun --browser=firefox appname.html

Note: If you are using Firefox, you can use CTRL+SHIFT+K to open the debug console.

Known issues
  • It is not currently possible to use Windows as a host platform.
  • Qt Quick will currently use the "software" backend, which will affect performance for complicated UIs and also disable the use of shader effects. A fix for this is coming soon.
  • Due to disabled threading support in WebAssembly at the moment, the configure string above will build Qt with no threading support. If your application relies on threading, this may lead to unexpected effects.

You can find a full list of known issues here: https://bugreports.qt.io/browse/QTBUG-63917

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