Set backend to PyQt5.

init.py

@@ -4,10 +4,8 @@
 from __future__ import (unicode_literals, absolute_import, division,
                         print_function)
 
-from traits.etsconfig.api import ETSConfig
-ETSConfig.toolkit = 'qt'
-
 import matplotlib as mpl
+mpl.use("Qt5Agg")
 
 from controlpanel import ControlPanel
 

mplfigure_qt.py

@@ -7,17 +7,20 @@ pointed out to me by Pierre Haessig, March 2014
 
 Source:
 http://enthought-dev.117412.n3.nabble.com/traitsui-matplotlib-editor-with-toolbar-using-qt-backend-td4026437.html
+
+April 2019: a few changes for accomodating PyQt5, based on
+https://pythonspot.com/pyqt5-matplotlib/
 """
 
-from pyface.qt import QtGui
-from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
+from PyQt5.QtWidgets import QWidget, QVBoxLayout
+from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
+from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT
 from matplotlib.figure import Figure
-# from matplotlib.backends.backend_qt4agg import NavigationToolbar2QTAgg
-from matplotlib.backends.backend_qt4agg import NavigationToolbar2QT
 
 from traits.api import Instance
 from traitsui.qt4.editor import Editor
 from traitsui.qt4.basic_editor_factory import BasicEditorFactory
+# 'qt4' is for compatibility, and will be probably replaced with 'qt' in the future
 
 
 class _MPLFigureEditor(Editor):
@@ -32,15 +35,13 @@ class _MPLFigureEditor(Editor):
         pass
 
     def _create_canvas(self, parent):
-        """ Create the MPL canvas. """
-        # matplotlib commands to create a canvas
-        frame = QtGui.QWidget()
+        """Create the MPL canvas."""
+        frame = QWidget()
         mpl_canvas = FigureCanvas(self.value)
         mpl_canvas.setParent(frame)
-        # mpl_toolbar = NavigationToolbar2QTAgg(mpl_canvas,frame)
         mpl_toolbar = NavigationToolbar2QT(mpl_canvas, frame)
 
-        vbox = QtGui.QVBoxLayout()
+        vbox = QVBoxLayout()
         vbox.addWidget(mpl_canvas)
         vbox.addWidget(mpl_toolbar)
         frame.setLayout(vbox)