Fix handling of getSaveFileName to be consistent

PyQt4 and PyQt5 handle getSaveFileName differently, returning either a filename or a filename,filter tuple respectively. PySide behaves as for PyQt5. This caused bug #3454 producing an 'format not supported' error as the tuple did not match any of the string types. This updates each API to return a tuple as per PyQt5 (following the principle of using the latest API as a target). For recent PyQt4 this means using getSaveFileNameAndFilter instead, for older PyQt4 we wrap the function to output a tuple. Figure saving has been tested on PySide, PyQt4 and PyQt5.
matplotlib · tacaswell · Sep 6, 2014 · Sep 4, 2014 · Sep 5, 2014 · Sep 4, 2014
commit 515b57c3c8a62632df04f7408ba4787bc21fa32a
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -715,7 +715,7 @@ def save_figure(self, *args):
            filters.append(filter)
        filters = ';;'.join(filters)

-        fname = _getSaveFileName(self.parent, "Choose a filename to save to",
+        fname, filter = _getSaveFileName(self.parent, "Choose a filename to save to",
                                 start, filters, selectedFilter)
        if fname:
            if startpath == '':

diff --git a/lib/matplotlib/backends/qt_compat.py b/lib/matplotlib/backends/qt_compat.py
@@ -78,21 +78,19 @@
        try:
            if sip.getapi("QString") > 1:
                # Use new getSaveFileNameAndFilter()
-                _get_save = QtGui.QFileDialog.getSaveFileNameAndFilter
+                _getSaveFileName = QtGui.QFileDialog.getSaveFileNameAndFilter
            else:
                # Use old getSaveFileName()
-                _getSaveFileName = QtGui.QFileDialog.getSaveFileName
+                def _getSaveFileName(*args, **kwargs):
+                    return QtGui.QFileDialog.getSaveFileName(*args, **kwargs), None
+
        except (AttributeError, KeyError):
            # call to getapi() can fail in older versions of sip
-            _getSaveFileName = QtGui.QFileDialog.getSaveFileName
+            def _getSaveFileName(*args, **kwargs):
+                return QtGui.QFileDialog.getSaveFileName(*args, **kwargs), None

    else:  # PyQt5 API
-
        from PyQt5 import QtCore, QtGui, QtWidgets
-
-        # Additional PyQt5 shimming to make it appear as for PyQt4
-
-        _get_save = QtWidgets.QFileDialog.getSaveFileName
        _getSaveFileName = QtWidgets.QFileDialog.getSaveFileName

    # Alias PyQt-specific functions for PySide compatibility.
@@ -112,11 +110,8 @@
        raise ImportError(
            "Matplotlib backend_qt4 and backend_qt4agg require PySide >=1.0.3")

-    _get_save = QtGui.QFileDialog.getSaveFileName
+    _getSaveFileName = QtGui.QFileDialog.getSaveFileName

-if _getSaveFileName is None:
-    def _getSaveFileName(self, msg, start, filters, selectedFilter):
-        return _get_save(self, msg, start, filters, selectedFilter)[0]

 # Apply shim to Qt4 APIs to make them look like Qt5
 if QT_API in (QT_API_PYQT, QT_API_PYQTv2, QT_API_PYSIDE):
@@ -128,3 +123,4 @@ def _getSaveFileName(self, msg, start, filters, selectedFilter):

    '''
    QtWidgets = QtGui
+