qt-creator/doc/qtcreator/src/python/creator-tutorial-python-application-qtquick.qdoc

// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \page creator-tutorial-python-application-qt-quick.html
    \previouspage creator-tutorials.html
    \nextpage creator-project-managing.html

    \ingroup creator-tutorials

    \title Creating a Qt for Python Application with Qt Quick

    \brief How to develop a Qt Quick application with Python.

    First, create a Qt for Python application project. Then, edit the boilerplate
    code to develop a small application that uses Qt Quick to display the text
    \e {Hello World} in several languages.

    \image qtcreator-new-qt-for-python-app-qt-quick-empty-project-ready.webp {A small Qt Quick application}

    \section1 Creating an Empty Project

    To create a Qt for Python application that has a main QML file:

    \list 1
        \li Select \uicontrol File > \uicontrol {New Project} >
            \uicontrol {Application (Qt for Python)} >
            \uicontrol {Qt Quick Application - Empty} > \uicontrol Choose.

            The \uicontrol {Project Location} dialog opens.
            \image qtcreator-new-qt-for-python-app-qt-quick-empty-project-location.webp {Project Location dialog}
        \li In \uicontrol {Name}, enter the project name. For example,
            \e {hello_world_quick}.
        \li In \uicontrol {Create in}, enter the path for the project files.
            For example, \c {C:\Qt\examples}.
        \li Select \uicontrol{Next} (on Windows and Linux) or \uicontrol Continue
            (on \macos) to open the \uicontrol {Define Project Details} dialog.
            \image qtcreator-new-qt-for-python-app-qt-quick-empty-project-details.webp {Define Project Details dialog}
        \li In \uicontrol {PySide version}, select the PySide version of
            the generated code.
        \li In \uicontrol {Interpreter}, select the Python interpreter to use for
            the project.
        \li Select the \uicontrol {Create new virtual environment} check box to
            use a clean \l{https://docs.python.org/3/library/venv.html}{Python}
            environment that is independent of your global Python installation.
        \li In \uicontrol {Path to virtual environment}, specify the directory
            where to create the environment.
        \li Select \uicontrol{Next} or \uicontrol Continue.
        \li Review the project settings, and select \uicontrol {Finish} (on
            Windows and Linux) or \uicontrol Done (on \macos) to create the
            project.
    \endlist

    The wizard generates the following files:

    \list
        \li \c {hello_world_quick.pyproject}, which lists the files in the Python
            project.
        \li \c {main.py}, which has some boilerplate code.
        \li \c {main.qml}, which imports Qt Quick controls.
    \endlist

    \section1 Adding Qt Quick Imports

    The wizard adds the following imports to the \c {main.py} source file for
    access to QGuiApplication and QQmlApplicationEngine:

    \badcode
    import sys
    from pathlib import Path

    from PySide6.QtGui import QGuiApplication
    from PySide6.QtQml import QQmlApplicationEngine
    \endcode

    \section1 Adding a Main Function

    The wizard also adds a main function, where it creates a QGuiApplication
    instance and passes system arguments to the QGuiApplication object:

    \badcode
    if __name__ == "__main__":
        app = QGuiApplication(sys.argv)
        ...
    \endcode

    \section1 Loading the QML File

    The following lines in the main class create a QQmlApplicationEngine
    instance and load the generated QML file to the engine object:

    \badcode
        ...
        engine = QQmlApplicationEngine()
        qml_file = Path(__file__).resolve().parent / "main.qml"
        engine.load(qml_file)
        ...
    \endcode

    Finally, the wizard adds code that checks whether the file was successfully
    loaded. If loading the file fails, the application exits with an error code.
    If loading succeeds, the wizard calls the \c app.exec() method to enter the
    Qt main loop and start executing the Qt code:

    \badcode
    ...
    if not engine.rootObjects():
        sys.exit(-1)
    sys.exit(app.exec())
    ...
    \endcode

    \section1 Designing the UI

    Open the \c {main.qml} file in the \uicontrol Edit mode to design a
    Qt Quick UI.

    \section2 Adding Imports

    Add imports for Qt Quick Controls and Layouts:

    \badcode
    import QtQuick
    import QtQuick.Window
    import QtQuick.Controls
    import QtQuick.Layouts
    \endcode

    \section2 Adding Properties and Functions

    The wizard adds a main window:

    \badcode
    Window {
        width: 640
        height: 480
        visible: true
        title: qsTr("Hello World")
    }
    \endcode

    Add a property and function to randomly select the language of the displayed
    text:

    \badcode
        ...
        readonly property list<string> texts: ["Hallo Welt", "Hei maailma",
                                           "Hola Mundo", "Привет мир"]

    function setText() {
        var i = Math.round(Math.random() * 3)
        text.text = texts[i]
    }
    \endcode

    \section2 Adding Qt Quick Controls

    Add \l {Text} and \l {Button} QML types within a \l {ColumnLayout} type to
    design the UI:

    \badcode
        ColumnLayout {
        anchors.fill:  parent

        Text {
            id: text
            text: "Hello World"
            Layout.alignment: Qt.AlignHCenter
        }
        Button {
            text: "Click me"
            Layout.alignment: Qt.AlignHCenter
            onClicked:  setText()
        }
    }
    \endcode

    You can also use \l{Qt Design Studio Manual}{\QDS} to design Qt Quick UIs.

    \section1 Running the Application

    Select the \inlineimage icons/run_small.png
    button to run the application.

    \sa {Creating a Qt for Python Application with Qt Widgets},
    {Develop Qt for Python Applications}
*/