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6. QT5 User Guide

6.1 Install Qt Creator​

The following example illustrates how to install Qt Creator on Ubuntu.

  1. Install the Build Essential package.
    sudo apt-get install build-essential
  1. Install Qt Creator.
    sudo apt-get install qtcreator
  1. Install QT5 related environment.
    sudo apt-get install qtbase5-dev qtchooser qt5-qmake qtbase5-dev-tools qtbase5-examples qt5-doc qtbase5-doc-html

The following applications are displayed after the installation is completed.

6.2 Compile Qt programs​

  1. Click the Qt Creator icon to enter the application.

  1. Choose Tools > Options. In the pop-up window, click Qt Versions and click Add.

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  1. Select qmake under /usr/bin.

  1. Click Kits, scroll down, set the Qt version to Qt5.15, and click OK.

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  1. Click Examples, type "Cube" in the input field, and click Cube OpenGL ES 2.0 example.

  1. In the pop-up window, click Keep Project and Open or Copy Project and Open as needed.

  1. Click Configure Project to enter the project.

  1. Click the play icon to run the project.

The project is successfully run. The next step is cross-compilation.

  1. Set up the cross-compilation environment. For details, refer to "1.11.2. Install cross-compilation tools".
    source <your toolchains directory>/environment-setup-armv8-2a-qcom-linux
  1. Go to the project's source directory and execute qmke to generate the Makefile.
    qmake

  1. Run the qmake and make commands for compilation.

  1. Transfer the compilation artifact to RUBIK Pi 3:

6.3 Configure the runtime environment​

Qt chooses a default Qt Platform Abstraction (QPA) plug-in based on the platform. Alternatively, set the QT_QPA_PLATFORM environment variable or -platform command line parameter to select another platform plug-in. Commonly used platform plug-ins include LinuxFB, Wayland, and EGLFS.

  • LinuxFB

    LinuxFB is displayed through Linux Framebuffer Device (FBDEV) which does not support hardware rendering, possibly resulting in poor display performance.

  • Wayland

    Wayland is a display service protocol that does not rely on a client-server architecture and is intended to replace the X Window System with Linux and other Unix-like operating systems. Weston is the implementation reference of the Wayland open-source display protocol.

  • EGLFS

    EGLFS is a GUI system implemented by Qt which does not support multiple windows. EGLFS uses opengles/egl for GPU rendering and then sends signals directly to DRM for display.

    EGLFS is the recommended plug-in for modern Embedded Linux devices that include a GPU.

Use Wayland on RUBIK Pi 3:

export XDG_RUNTIME_DIR=/dev/socket/weston  
export WAYLAND_DISPLAY=wayland-1  
export QT_QPA_PLATFORM='wayland'  
cd /opt  
./cube

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6.4 PyQt5​

RUBIK Pi 3 supports PyQt5. The following example shows an example of PyQt5 demo.

import sys
from PyQt5.QtWidgets import QApplication, QWidget

app = QApplication(sys.argv)

w = QWidget()
w.resize(550, 500)
w.move(600, 300)
w.setWindowTitle('RUBIK Pi 3 PyQt5 demo title')
w.show()
sys.exit(app.exec_())

Transfer pyqt5.py to RUBIK Pi 3. For example, use the ADB method.

adb push pyqt5.py /opt

Run the following commands on RUBIK Pi 3 to run the demo.

export XDG_RUNTIME_DIR=/dev/socket/weston
export WAYLAND_DISPLAY=wayland-1
export QT_QPA_PLATFORM='wayland'
cd /opt
python3 pyqt5.py

The execution result is as follows:

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