FigureCanvaQtAgg : diffrence a right and left click

Question

I'm trying to use a FigureCanveQtAgg to embedded a Matplotlib figure in a Qt window. That works perfectly but I have some troubles to ditinguish between a left and a right click when I click on the figure.

Here is a simpler version of what I've done (I had a problem with the left click some time ago so I've taken the answer of this previous question and I've copied pasted it here : How to draw a circle on a FigureCanvasQTAgg on mouse click).

from PySide2 import QtCore, QtGui, QtWidgets

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure

import numpy as np


class PainterCanvas(FigureCanvas):
    def __init__(self, parent=None, width=5, height=4, dpi=100):
        fig = Figure(figsize=(width, height), dpi=dpi)
        FigureCanvas.__init__(self, fig)
        self.setParent(parent)
        self._instructions = []
        self.axes = self.figure.add_subplot(111)

    def paintEvent(self, event):
        super().paintEvent(event)
        painter = QtGui.QPainter(self)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        width, height = self.get_width_height()
        for x, y, rx, ry, br_color in self._instructions:
            x_pixel, y_pixel_m = self.axes.transData.transform((x, y))
            # In matplotlib, 0,0 is the lower left corner,
            # whereas it's usually the upper right
            # for most image software, so we'll flip the y-coor
            y_pixel = height - y_pixel_m
            painter.setBrush(QtGui.QColor(br_color))
            painter.drawEllipse( QtCore.QPoint(x_pixel, y_pixel), rx, ry)

    def create_oval(self, x, y, radius_x=5, radius_y=5, brush_color="red"):
        self._instructions.append([x, y, radius_x, radius_y, brush_color])
        self.update()


class MyPaintWidget(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        self.canvas = PainterCanvas()
        self.canvas.mpl_connect("button_press_event", self._on_left_click)
        x = np.arange(0, 10, 0.1)
        y = np.cos(x)
        self.canvas.axes.plot(x, y)

        layout_canvas = QtWidgets.QVBoxLayout(self)
        layout_canvas.addWidget(self.canvas)

    def _on_left_click(self, event):
        self.canvas.create_oval(event.xdata, event.ydata, brush_color="green")


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)

    w = MyPaintWidget()
    w.show()
    sys.exit(app.exec_())

It perfectly work for what I wanted back then. But, now I need to distinguish between left and right click. I think the problem is because with the function mpl_connect() I can only use the "button_press_event" event. But is there a way to distinguish between right and left click ?

What I would to achieve is : - if user left click : it draws a green circle like now - if user right click : it opens context menu with functions

Thanks !

score 1 · Accepted Answer · answered Jan 27 '20 at 10:47

You can use the button attribute of event in MyPaintWidget._on_left_click to determine which button was pressed. This attribute is an enumerated constant of type matplotlib.backend_bases.MouseButton. So to distinguish between left- and right-button presses you could do something like this

from matplotlib.backend_bases import MouseButton

...

class MyPaintWidget(QtWidgets.QWidget):

    ....

    def _on_left_click(self, event):    
        if event.button == MouseButton.LEFT:
            # draw circle
        elif event.button == MouseButton.RIGHT:
            # open context menu

FigureCanvaQtAgg : diffrence a right and left click

1 Answers1