pyqtgraph: How to add radiobuttons on a figure legend?

I want to control which curves are displayed at the figure by using the radiobuttons floating on the left-top corner, which will work also as a legend. How can I do that?

Answer

This could be achieved by inheiring pg.LegendItem and overriding addItem method. In it you need to create widgets and place them into layout. You can use QGraphicsProxyWidget to display QRadioButton on QGraphicsScene (PlotWidget).

import pyqtgraph as pg
from pyqtgraph.graphicsItems.LegendItem import ItemSample
from PyQt5 import QtCore, QtGui, QtWidgets

class LegendItem(pg.LegendItem):

    clicked = QtCore.pyqtSignal(int)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._group = QtWidgets.QButtonGroup()

    def addItem(self, item, name):
        widget = QtWidgets.QRadioButton(name)
        palette = widget.palette()
        palette.setColor(QtGui.QPalette.Window, QtCore.Qt.transparent)
        palette.setColor(QtGui.QPalette.WindowText, QtCore.Qt.white)
        widget.setPalette(palette)
        self._group.addButton(widget)
        row = self.layout.rowCount()
        widget.clicked.connect(lambda: self.clicked.emit(row))
        proxy = item.scene().addWidget(widget)
        if isinstance(item, ItemSample):
            sample = item
        else:
            sample = ItemSample(item)
        self.layout.addItem(proxy, row, 0)
        self.layout.addItem(sample, row, 1)
        self.items.append((proxy, sample))
        self.updateSize()

if __name__ == '__main__':
    app = QtWidgets.QApplication([])

    plt = pg.PlotWidget()
    plt.setWindowTitle('Legend with radiobuttons')
    
    legend = LegendItem(verSpacing=5, horSpacing=5)
    legend.setParentItem(plt.getViewBox())

    plt.plotItem.legend = legend

    c1 = plt.plot([1,3,2,4], pen='r', symbol='o', symbolPen='r', symbolBrush=0.5, name='red plot') 
    c2 = plt.plot([2,1,4,3], pen='g', fillLevel=0, fillBrush=(255,255,255,30), name='green plot')

    def onClicked(index):
        print("{} clicked".format(index))

    legend.clicked.connect(onClicked)

    plt.show()

    app.exec()