Unset the canvas manager when saving the figure.

anntzer · anntzer · commit c92e48b8d837 · 2018-01-22T13:11:16.000-08:00
Saving a figure may involve temporarily resizing the canvas (e.g. due to
different dpi), but we don't want that resize to be propagated to the
actual GUI widget.  Ensure this by temporarily unsetting the manager as
well.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1772,6 +1772,7 @@ def __init__(self, figure):
         self._is_saving = False
         figure.set_canvas(self)
         self.figure = figure
+        self.manager = None
         # a dictionary from event name to a dictionary that maps cid->func
         self.callbacks = cbook.CallbackRegistry()
         self.widgetlock = widgets.LockDraw()
@@ -2149,6 +2150,15 @@ def print_figure(self, filename, dpi=None, facecolor=None, edgecolor=None,
 
         """
         self._is_saving = True
+        # Remove the figure manager, if any, to avoid resizing the GUI widget.
+        # Having *no* manager and a *None* manager are currently different (see
+        # Figure.show); should probably be normalized to None at some point.
+        _no_manager = object()
+        if hasattr(self, 'manager'):
+            manager = self.manager
+            del self.manager
+        else:
+            manager = _no_manager
 
         if format is None:
             # get format from filename, or from backend's default filetype
@@ -2267,8 +2277,9 @@ def print_figure(self, filename, dpi=None, facecolor=None, edgecolor=None,
             self.figure.set_facecolor(origfacecolor)
             self.figure.set_edgecolor(origedgecolor)
             self.figure.set_canvas(self)
+            if manager is not _no_manager:
+                self.manager = manager
             self._is_saving = False
-            #self.figure.canvas.draw() ## seems superfluous
         return result
 
     @classmethod
