QtWayland
What is QtWayland?
QtWayland is a Qt 5 module that wraps the functionality of Wayland. QtWayland is separated into a client and server side. The client side is the wayland platform plugin, and provides a way to run Qt applications as Wayland clients. The server side is the Qt Wayland Compositor API, and allows users to write their own Wayland compositors.
What is Wayland
Wayland is a protocol for a compositor to talk to its clients as well as a C library implementation of that protocol. For more detailed information you should visit the Wayland project homepage
How can I get binaries for Qt Wayland?
Starting with Qt 5.11. the Qt installer should include binaries for Qt Wayland.
If you are using Qt provided by your Linux distribution there is most likely a separate package for Qt Wayland, i.e. qt5-wayland (Arch Linux), or two separate packages, i.e. qtwaylandclient5 and qtwaylandcompositor5-dev (Ubuntu 17.10). Beware that distros may ship really old versions of Qt though, and the compositor API was first released as stable with Qt 5.8.
You can however also build it from source yourself in case you want to use the development version or apply custom patches. See section below.
Where can I find the code for QtWayland?
How do I build QtWayland?
Ubuntu 14.04
Ubuntu 14.04 contains all necessary dependencies, so it is no longer necessary to build Wayland yourself.
The following packages are required (list may be incomplete)
- libwayland-dev
- libwayland-egl1-mesa
- libwayland-server0
- libgles2-mesa-dev
- libxkbcommon-dev
Qt dependency
You need Qt5.8 or newer for the compositor API. The modules you need at the very least are:
qtbase
qtdeclarative
Building the QtWayland module
Once you have a working build of Qt 5, then pull down the latest QtWayland module code and configure with "qmake". Make sure that you use the version of qmake that you get with Qt 5 here.
git clone git://code.qt.io/qt/qtwayland.git
cd qtwayland
git checkout v5.10.0 # replace with your qt version
qmake
make
make install
How do I use QtWayland?
Run Qt applications as Wayland clients
When you build the QtWayland module, you should get a new platform plugin for wayland. To use it you must first already have a Wayland compositor running. This could be either the Weston reference compositor provided by the Wayland project, or a Qt example compositor provided by QtWayland. Regardless the only thing you need to do as an application developer to run your GUI application as a wayland client is tell the application to use the right platform plugin:
./application -platform wayland
or:
export QT_QPA_PLATFORM=wayland
./application
Create and Run your own Wayland Compositor with Qt5
Running example compositors
The QtWayland module provides a couple of example compositors that demonstrate how the Qt Wayland Compositor API works. These are built in the examples folder of the QtWayland module. You may need to explicitly build them (depending on how you configured Qt):
cd qtwayland
make sub-examples
These examples represent the server side of Wayland, so they do not use the wayland platform plugin, but rather whatever platform you need to run on. Generally this is going to be either eglfs, kms, or if you want to run in X11 xcb. You can also run a nested compositor if you run the compositor on the wayland platform plugin.
If you wanted to run the pure-qml compositor in X11 you would run the following:
cd qtwayland/examples/wayland/pure-qml
./pure-qml -platform xcb
And now that you have a Wayland compositor running, you can connect and display Wayland clients.
Creating your own compositor
Compositors can be implemented using QML, or you can use the C++ API if you need more low-level control.
- QML-based: See minimal-qml and pure-qml. Tutorial, talk
- C++-based: See the minimal-cpp and qwindow-compositor examples.
The project file will need to use the compositor module (i.e. add in the .pro file QT += waylandcompositor).
Troubleshooting
libGL linker issues
If you face linker errors related to libGL and undefined references, it may be necessary to compile Qt5 and link it with the self compiled mesa. Maybe due to the way that mesa was compiled and installed, the configure script will require to explicitly define the version of OpenGL to be used with: ./configure -opengl es2