Extending QML - Plugins Example

This is the last of a series of 6 examples forming a tutorial about extending QML with Python.

This example refers to the Python version of using a QML plugin in Python. The idea of plugins in Python is non-existent because Python modules are dynamically loaded anyway. We use this idea and our QML type registration decorators - @QmlElement / @QmlNamedElement - to register the QML modules as they are imported. The pyside6-qml tool does this for you by simply pointing to the .qml file.

Running the Example

pyside6-qml examples/qml/tutorials/extending-qml/chapter6-plugins/app.qml -I examples/qml/tutorials/extending-qml/chapter6-plugins/Charts

Download this example

app.qml

// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

import QtQuick
import Charts 1.0

Item {
    width: 300; height: 200

    PieChart {
        anchors.centerIn: parent
        width: 100; height: 100

        slices: [
            PieSlice {
                anchors.fill: parent
                color: "red"
                fromAngle: 0; angleSpan: 110
            },
            PieSlice {
                anchors.fill: parent
                color: "black"
                fromAngle: 110; angleSpan: 50
            },
            PieSlice {
                anchors.fill: parent
                color: "blue"
                fromAngle: 160; angleSpan: 100
            }
        ]
    }
}

Charts/piechart.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

from PySide6.QtCore import Property
from PySide6.QtQml import QmlElement, ListProperty
from PySide6.QtQuick import QQuickItem

from pieslice import PieSlice

# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "Charts"
QML_IMPORT_MAJOR_VERSION = 1


@QmlElement
class PieChart(QQuickItem):
    def __init__(self, parent=None):
        super().__init__(parent)
        self._slices = []
        self._name = ''

    @Property(str, final=True)
    def name(self):
        return self._name

    @name.setter
    def name(self, name):
        self._name = name

    def slice(self, n):
        return self._slices[n]

    def sliceCount(self):
        return len(self._slices)

    def append_and_setparent(self, slice):
        self._slices.append(slice)
        slice.setParentItem(self)

    slices = ListProperty(PieSlice, append_and_setparent)

Charts/pieslice.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

from PySide6.QtCore import Property, QRectF
from PySide6.QtGui import QColor, QPainter, QPen
from PySide6.QtQuick import QQuickPaintedItem
from PySide6.QtQml import QmlElement

# To be used on the @QmlElement decorator
# (QML_IMPORT_MINOR_VERSION is optional)
QML_IMPORT_NAME = "Charts"
QML_IMPORT_MAJOR_VERSION = 1


@QmlElement
class PieSlice(QQuickPaintedItem):
    def __init__(self, parent=None):
        super().__init__(parent)

        self._color = QColor()
        self._from_angle = 0
        self._angle_span = 0

    @Property(QColor, final=True)
    def color(self):
        return self._color

    @color.setter
    def color(self, color):
        self._color = QColor(color)

    @Property(int, final=True)
    def fromAngle(self):
        return self._from_angle

    @fromAngle.setter
    def fromAngle(self, fromAngle):
        self._from_angle = fromAngle

    @Property(int, final=True)
    def angleSpan(self):
        return self._angle_span

    @angleSpan.setter
    def angleSpan(self, angleSpan):
        self._angle_span = angleSpan

    def paint(self, painter):
        painter.setPen(QPen(self._color, 2))
        painter.setRenderHint(QPainter.RenderHint.Antialiasing, True)

        rect = QRectF(0, 0, self.width(), self.height()).adjusted(1, 1, -1, -1)
        painter.drawPie(rect, self._from_angle * 16, self._angle_span * 16)