Unable to implement mpl_connect - user-interface

Question

I'm working on a GUI that basically hold multiple widgets that each contain a figure as well as a few buttons/whatever. One of the figures is supposed to be interactive, calling a function whenever the user clicks on any part of the plot. Yet I can't get the function to fire using mpl_connect, even after playing with focus and whatnot. I'm somewhat new to PySide/Qt, so I don't exactly understand why my code is behaving like this (I've been searching for days for a solution, but haven't found anything about it).
I used Qt Designer to create the layout for the GUI. I'm using Spyder from Anaconda 2.2.0 (32-bit), Python 2.7, and PySide to develop the GUI. If it's any help, I come from more of a MATLAB background where I developed a full version of the GUI I'm trying to make in Python.
Below is the relevant code (scroll down a bit to see where the problem is):
from PySide import QtCore, QtGui
from PySide.QtCore import *
from PySide.QtGui import *
import numpy as np
import matplotlib
matplotlib.use('Qt4Agg')
matplotlib.rcParams['backend.qt4']='PySide'
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.backends.backend_qt4agg import NavigationToolbar2QTAgg as NavigationToolbar
import matplotlib.pyplot as plt
from PySide.QtGui import QPalette, QCursor
import matplotlib.colors as colors
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(1316, 765)
self.centralwidget = QtGui.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.widget = QtGui.QWidget(self.centralwidget)
self.widget.setGeometry(QtCore.QRect(75, 40, 375, 490))
self.widget.setObjectName("widget")
color = self.centralwidget.palette().color(QPalette.Window)
self.leftPlot = MatplotlibWidget(None,'','','',False,color)
self.setupPlot(self.widget,self.leftPlot)
self.leftPlot.figure.tight_layout()
self.leftImage = self.leftPlot.axes.imshow(self.defaultSlide, cmap = mymap)
Snippet of interest:
self.leftPlot.figure.canvas.setFocusPolicy(QtCore.Qt.StrongFocus)
self.leftPlot.figure.canvas.setFocus()
cid = self.leftPlot.figure.canvas.mpl_connect('button_release_event', self.getCoordinates) # doesn't get called
plt.show()
def getCoordinates(self, event):
print 'dasdsadadsa'
print 'button=%d, x=%d, y=%d, xdata=%f, ydata=%f'%(event.button, event.x, event.y, event.xdata, event.ydata)
The rest:
class MatplotlibWidget(FigureCanvas):
def __init__(self, parent=None,xlabel='x',ylabel='y',title='Title',showTicks=False,color=None):
super(MatplotlibWidget, self).__init__(Figure())
self.setParent(parent)
if color != None:
self.figure = Figure(facecolor=(color.red()/256.0,color.green()/256.0,color.blue()/256.0),frameon=0)
else:
self.figure = Figure(frameon=0)
self.canvas = FigureCanvas(self.figure)
self.axes = self.figure.add_subplot(111)
self.axes.set_xlabel(xlabel)
self.axes.set_ylabel(ylabel)
self.axes.set_title(title)
self.axes.get_xaxis().set_visible(showTicks)
self.axes.get_yaxis().set_visible(showTicks)
class ControlMainWindow(QtGui.QMainWindow):
def __init__(self, parent=None):
super(ControlMainWindow, self).__init__(parent)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
plt.show()
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
mySW = ControlMainWindow()
mySW.show()
sys.exit(app.exec_())
I'm aware the code is messy, but any input is greatly appreciated.

Answer 1

Update (2015-09-04) : I've updated the MWE I provided as part of my original answer to use instead the approach that is suggested in the matplotlib documentation to embed a mpl figure in an application. This approach does not use the pyplot interface (as in my original answer) and use the Object Oriented API of mpl instead. Also, since all the mpl artists (figure, axes, etc.) know each other, there is no need to explicitly create new class variables. This allows a structure of code that is, IMO, easier to read and to maintain.
The problem comes from the fact that you are not connecting correctly your event to self.leftPlot (FigureCanvasQTAgg), but to self.leftPlot.figure.canvas (FigureCanvasQTAgg.figure.FigureCanvasQTAgg) instead. You are creating a canvas within a canvas in the MatplotlibWidget class (which is already a subclass of FigureCanvasQTAgg). You only need to create one mpl canvas, pass a figure to it, and then connect the event to it directly.
I've put together a MWE to demonstrate how this can be done using the Object Oriented API of Matplotlib as suggested in the documentation:
from PySide import QtGui
import numpy as np
import sys
import matplotlib as mpl
mpl.use('Qt4Agg')
mpl.rcParams['backend.qt4']='PySide'
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg
class ControlMainWindow(QtGui.QMainWindow):
def __init__(self, parent=None):
super(ControlMainWindow, self).__init__(parent)
self.setupUi()
def setupUi(self):
figure = mpl.figure.Figure(figsize=(5, 5))
leftPlot = MatplotlibWidget(figure)
self.setCentralWidget(leftPlot)
class MatplotlibWidget(FigureCanvasQTAgg):
def __init__(self, fig):
super(MatplotlibWidget, self).__init__(fig)
#-- set up an axe artist --
ax = fig.add_axes([0.1, 0.1, 0.85, 0.85])
ax.plot(np.arange(15), np.arange(15))
self.draw()
#---- setup event ----
self.mpl_connect('button_press_event', self.onclick)
def onclick(self, event):
x, y = event.x, event.y
print(x, y)
if x != None and y != None:
ax = self.figure.axes[0]
ax.plot(event.xdata, event.ydata, 'ro')
self.draw()
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
mySW = ControlMainWindow()
mySW.show()
sys.exit(app.exec_())
The code above results in: