Deprecate NavigationToolbar2QT.parent.

anntzer · anntzer · commit 52a204b4f9c3 · 2020-03-18T21:14:45.000+01:00
This attribute shadows the normal Qt method parent() (which also returns
the parent window...), which is a source of confusion.  After the
deprecation period passes, the parent property can be deleted and
parent() will simply be the method inherited from QToolBar.

Note that the attribute is not present on other backend toolbars either.
diff --git a/doc/api/next_api_changes/deprecations.rst b/doc/api/next_api_changes/deprecations.rst
@@ -370,3 +370,9 @@ mathtext ``Glue`` helper classes
 The ``Fil``, ``Fill``, ``Filll``, ``NegFil``, ``NegFill``, ``NegFilll``, and
 ``SsGlue`` classes in the :mod:`matplotlib.mathtext` module are deprecated.
 As an alternative, directly construct glue instances with ``Glue("fil")``, etc.
+
+NavigationToolbar2QT.parent
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This attribute is deprecated.  In order to access the parent window, use
+``toolbar.canvas.parent()``.  Once the deprecation period is elapsed, it will
+also be accessible as ``toolbar.parent()``.
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -660,14 +660,19 @@ class NavigationToolbar2QT(NavigationToolbar2, QtWidgets.QToolBar):
     def __init__(self, canvas, parent, coordinates=True):
         """coordinates: should we show the coordinates on the right?"""
         self.canvas = canvas
-        self.parent = parent
+        self._parent = parent
         self.coordinates = coordinates
         self._actions = {}
         """A mapping of toolitem method names to their QActions"""
 
         QtWidgets.QToolBar.__init__(self, parent)
         NavigationToolbar2.__init__(self, canvas)
 
+    @cbook.deprecated("3.3", alternative="self.canvas.parent()")
+    @property
+    def parent(self):
+        return self._parent
+
     def _icon(self, name, color=None):
         if is_pyqt5():
             name = name.replace('.png', '_large.png')
@@ -718,7 +723,7 @@ def edit_parameters(self):
         axes = self.canvas.figure.get_axes()
         if not axes:
             QtWidgets.QMessageBox.warning(
-                self.parent, "Error", "There are no axes to edit.")
+                self.canvas.parent(), "Error", "There are no axes to edit.")
             return
         elif len(axes) == 1:
             ax, = axes
@@ -735,7 +740,8 @@ def edit_parameters(self):
                 if titles[i] in duplicate_titles:
                     titles[i] += f" (id: {id(ax):#x})"  # Deduplicate titles.
             item, ok = QtWidgets.QInputDialog.getItem(
-                self.parent, 'Customize', 'Select axes:', titles, 0, False)
+                self.canvas.parent(),
+                'Customize', 'Select axes:', titles, 0, False)
             if not ok:
                 return
             ax = axes[titles.index(item)]
