legend.py

"""PySide6 port of the Legend example from Qt v5.x"""

import sys
from PySide6.QtCore import Qt, QRectF
from PySide6.QtGui import QBrush, QColor, QPainter, QPen
from PySide6.QtWidgets import (QApplication, QDoubleSpinBox,
    QFormLayout, QGridLayout, QGroupBox, QPushButton, QWidget)
from PySide6.QtCharts import QBarSeries, QBarSet, QChart, QChartView

class MainWidget(QWidget):
    def __init__(self, parent=None):
        super(MainWidget, self).__init__(parent)
        self.chart = QChart()
        self.series = QBarSeries()

        self.main_layout = QGridLayout()
        self.button_layout = QGridLayout()
        self.font_layout = QFormLayout()

        self.font_size = QDoubleSpinBox()

        self.legend_posx = QDoubleSpinBox()
        self.legend_posy = QDoubleSpinBox()
        self.legend_width = QDoubleSpinBox()
        self.legend_height = QDoubleSpinBox()

        self.detach_legend_button = QPushButton("Toggle attached")
        self.detach_legend_button.clicked.connect(self.toggle_attached)
        self.button_layout.addWidget(self.detach_legend_button, 0, 0)

        self.add_set_button = QPushButton("add barset")
        self.add_set_button.clicked.connect(self.add_barset)
        self.button_layout.addWidget(self.add_set_button, 2, 0)

        self.remove_barset_button = QPushButton("remove barset")
        self.remove_barset_button.clicked.connect(self.remove_barset)
        self.button_layout.addWidget(self.remove_barset_button, 3, 0)

        self.align_button = QPushButton("Align (Bottom)")
        self.align_button.clicked.connect(self.set_legend_alignment)
        self.button_layout.addWidget(self.align_button, 4, 0)

        self.bold_button = QPushButton("Toggle bold")
        self.bold_button.clicked.connect(self.toggle_bold)
        self.button_layout.addWidget(self.bold_button, 8, 0)

        self.italic_button = QPushButton("Toggle italic")
        self.italic_button.clicked.connect(self.toggle_italic)
        self.button_layout.addWidget(self.italic_button, 9, 0)

        self.legend_posx.valueChanged.connect(self.update_legend_layout)
        self.legend_posy.valueChanged.connect(self.update_legend_layout)
        self.legend_width.valueChanged.connect(self.update_legend_layout)
        self.legend_height.valueChanged.connect(self.update_legend_layout)

        legend_layout = QFormLayout()
        legend_layout.addRow("HPos", self.legend_posx)
        legend_layout.addRow("VPos", self.legend_posy)
        legend_layout.addRow("Width", self.legend_width)
        legend_layout.addRow("Height", self.legend_height)

        self.legend_settings = QGroupBox("Detached legend")
        self.legend_settings.setLayout(legend_layout)
        self.button_layout.addWidget(self.legend_settings)
        self.legend_settings.setVisible(False)

        # Create chart view with the chart
        self.chart_view = QChartView(self.chart, self)

        # Create spinbox to modify font size
        self.font_size.setValue(self.chart.legend().font().pointSizeF())
        self.font_size.valueChanged.connect(self.font_size_changed)

        self.font_layout.addRow("Legend font size", self.font_size)

        # Create layout for grid and detached legend
        self.main_layout.addLayout(self.button_layout, 0, 0)
        self.main_layout.addLayout(self.font_layout, 1, 0)
        self.main_layout.addWidget(self.chart_view, 0, 1, 3, 1)
        self.setLayout(self.main_layout)

        self.create_series()

    def create_series(self):
        self.add_barset()
        self.add_barset()
        self.add_barset()
        self.add_barset()

        self.chart.addSeries(self.series)
        self.chart.setTitle("Legend detach example")
        self.chart.createDefaultAxes()

        self.chart.legend().setVisible(True)
        self.chart.legend().setAlignment(Qt.AlignBottom)

        self.chart_view.setRenderHint(QPainter.Antialiasing)

    def show_legend_spinbox(self):
        self.legend_settings.setVisible(True)
        chart_viewrect = self.chart_view.rect()

        self.legend_posx.setMinimum(0)
        self.legend_posx.setMaximum(chart_viewrect.width())
        self.legend_posx.setValue(150)

        self.legend_posy.setMinimum(0)
        self.legend_posy.setMaximum(chart_viewrect.height())
        self.legend_posy.setValue(150)

        self.legend_width.setMinimum(0)
        self.legend_width.setMaximum(chart_viewrect.width())
        self.legend_width.setValue(150)

        self.legend_height.setMinimum(0)
        self.legend_height.setMaximum(chart_viewrect.height())
        self.legend_height.setValue(75)

    def hideLegendSpinbox(self):
        self.legend_settings.setVisible(False)

    def toggle_attached(self):
        legend = self.chart.legend()
        if legend.isAttachedToChart():
            legend.detachFromChart()
            legend.setBackgroundVisible(True)
            legend.setBrush(QBrush(QColor(128, 128, 128, 128)))
            legend.setPen(QPen(QColor(192, 192, 192, 192)))

            self.show_legend_spinbox()
            self.update_legend_layout()
        else:
            legend.attachToChart()
            legend.setBackgroundVisible(False)
            self.hideLegendSpinbox()
        self.update()

    def add_barset(self):
        series_count = self.series.count()
        bar_set = QBarSet(f"set {series_count}")
        delta = series_count * 0.1
        bar_set.append([1 + delta, 2 + delta, 3 + delta, 4 + delta])
        self.series.append(bar_set)

    def remove_barset(self):
        sets = self.series.barSets()
        len_sets = len(sets)
        if len_sets > 0:
            self.series.remove(sets[len_sets - 1])

    def set_legend_alignment(self):
        button = self.sender()
        legend = self.chart.legend()
        alignment = legend.alignment()

        if alignment == Qt.AlignTop:
            legend.setAlignment(Qt.AlignLeft)
            if button:
                button.setText("Align (Left)")
        elif alignment == Qt.AlignLeft:
            legend.setAlignment(Qt.AlignBottom)
            if button:
                button.setText("Align (Bottom)")
        elif alignment == Qt.AlignBottom:
            legend.setAlignment(Qt.AlignRight)
            if button:
                button.setText("Align (Right)")
        else:
            if button:
                button.setText("Align (Top)")
            legend.setAlignment(Qt.AlignTop)

    def toggle_bold(self):
        legend = self.chart.legend()
        font = legend.font()
        font.setBold(not font.bold())
        legend.setFont(font)

    def toggle_italic(self):
        legend = self.chart.legend()
        font = legend.font()
        font.setItalic(not font.italic())
        legend.setFont(font)

    def font_size_changed(self):
        legend = self.chart.legend()
        font = legend.font()
        font_size  = self.font_size.value()
        if font_size < 1:
            font_size = 1
        font.setPointSizeF(font_size)
        legend.setFont(font)

    def update_legend_layout(self):
        legend = self.chart.legend()

        rect = QRectF(self.legend_posx.value(),
            self.legend_posy.value(),
            self.legend_width.value(),
            self.legend_height.value())
        legend.setGeometry(rect)

        legend.update()

if __name__ == "__main__":
    app = QApplication(sys.argv)
    w = MainWidget()
    available_geometry = w.screen().availableGeometry()
    size = available_geometry.height() * 0.75
    w.setFixedSize(size, size)
    w.show()
    sys.exit(app.exec_())