@@ -93,8 +93,7 @@ def do_constrained_layout(fig, renderer, h_pad, w_pad,
9393 """
9494
9595# make layoutgrid tree...
96- _layoutgrids = None
97- _layoutgrids = _make_layoutgrids (fig ,_layoutgrids )
96+ _layoutgrids = _make_layoutgrids (fig ,None )
9897if not _layoutgrids ['hasgrids' ]:
9998_api .warn_external ('There are no gridspecs with layoutgrids. '
10099'Possibly did not call parent GridSpec with the'
@@ -134,6 +133,14 @@ def do_constrained_layout(fig, renderer, h_pad, w_pad,
134133
135134
136135def _make_layoutgrids (fig ,_layoutgrids ):
136+ """
137+ Make the layoutgrid tree.
138+
139+ (Sub)Figures get a layoutgrid so we can have figure margins.
140+
141+ Gridspecs that are attached to axes get a layoutgrid so axes
142+ can have margins.
143+ """
137144
138145if _layoutgrids is None :
139146_layoutgrids = dict ()
@@ -144,7 +151,10 @@ def _make_layoutgrids(fig, _layoutgrids):
144151else :
145152# subfigure
146153gs = fig ._subplotspec .get_gridspec ()
154+ # its possible the gridspec containing this subfigure hasn't
155+ # been added to the tree yet:
147156_layoutgrids = _make_layoutgrids_gs (_layoutgrids ,gs )
157+ # add the layoutgrid for the subfigure:
148158parentlb = _layoutgrids [gs ]
149159_layoutgrids [fig ]= layoutgrid .LayoutGrid (
150160parent = parentlb ,
@@ -154,9 +164,11 @@ def _make_layoutgrids(fig, _layoutgrids):
154164nrows = 1 ,ncols = 1 ,
155165parent_pos = (fig ._subplotspec .rowspan ,
156166fig ._subplotspec .colspan ))
167+ # recursively do all subfigures in this figure...
157168for sfig in fig .subfigs :
158169_layoutgrids = _make_layoutgrids (sfig ,_layoutgrids )
159170
171+ # for each axes at the local level add its gridspec:
160172for ax in fig ._localaxes .as_list ():
161173if hasattr (ax ,'get_subplotspec' ):
162174gs = ax .get_subplotspec ().get_gridspec ()
@@ -166,9 +178,14 @@ def _make_layoutgrids(fig, _layoutgrids):
166178
167179
168180def _make_layoutgrids_gs (_layoutgrids ,gs ):
181+ """
182+ Make the layoutgrid for a gridspec (and anything nested in the gridspec)
183+ """
169184
170185if gs in _layoutgrids or gs .figure is None :
171186return _layoutgrids
187+ # in order to do constrained_layout there has to be at least *one*
188+ # gridspec in the tree:
172189_layoutgrids ['hasgrids' ]= True
173190if not hasattr (gs ,'_subplot_spec' ):
174191# normal gridspec
@@ -182,17 +199,20 @@ def _make_layoutgrids_gs(_layoutgrids, gs):
182199width_ratios = gs .get_width_ratios (),
183200height_ratios = gs .get_height_ratios ())
184201else :
185- # this is agridspec inside a subplotspec...
202+ # this is agridspecfromsubplotspec:
186203subplot_spec = gs ._subplot_spec
187204parentgs = subplot_spec .get_gridspec ()
205+ # if its a nested gridspec its possible the parent is not in there yet:
188206if parentgs not in _layoutgrids :
189207_layoutgrids = _make_layoutgrids_gs (_layoutgrids ,parentgs )
190208subspeclb = _layoutgrids [parentgs ]
191- _layoutgrids [str (gs )+ 'top' ]= layoutgrid .LayoutGrid (
192- parent = subspeclb ,
193- name = subspeclb .name + '.top' + layoutgrid .seq_id (),
194- nrows = 1 ,ncols = 1 ,
195- parent_pos = (subplot_spec .rowspan ,subplot_spec .colspan ))
209+ # gridspecfromsubplotspec need an outer container:
210+ if str (gs )+ 'top' not in _layoutgrids :
211+ _layoutgrids [str (gs )+ 'top' ]= layoutgrid .LayoutGrid (
212+ parent = subspeclb ,
213+ name = subspeclb .name + '.top' + layoutgrid .seq_id (),
214+ nrows = 1 ,ncols = 1 ,
215+ parent_pos = (subplot_spec .rowspan ,subplot_spec .colspan ))
196216_layoutgrids [gs ]= layoutgrid .LayoutGrid (
197217parent = _layoutgrids [str (gs )+ 'top' ],
198218name = (_layoutgrids [str (gs )+ 'top' ].name + '.gridspec' +