ENH: add ability to remove layout engine

tacaswell · tacaswell · commit cb0410a44f11 · 2022-02-11T15:21:18.000-05:00
This may be too simplistic as it just sets it to None which gives you ability
to "go through zero" and change to an incompatible layout engine.
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2313,7 +2313,9 @@ def _check_layout_engines_compat(self, old, new):
         If the figure has used the old engine and added a colorbar then the
         value of colorbar_gridspec must be the same on the new engine.
         """
-        if old is None or old.colorbar_gridspec == new.colorbar_gridspec:
+        if old is None or new is None:
+            return True
+        if old.colorbar_gridspec == new.colorbar_gridspec:
             return True
         # colorbar layout different, so check if any colorbars are on the
         # figure...
@@ -2329,10 +2331,12 @@ def set_layout_engine(self, layout=None, **kwargs):
 
         Parameters
         ----------
-        layout: {'constrained', 'tight'} or `~.LayoutEngine`
+        layout: {'constrained', 'tight', 'none'} or `~.LayoutEngine`
             'constrained' will use `~.ConstrainedLayoutEngine`, 'tight' will
             use `~.TightLayoutEngine`.  Users and libraries can define their
             own layout engines as well.
+
+            The string 'none' removes layout engine.
         kwargs: dict
             The keyword arguments are passed to the layout engine to set things
             like padding and margin sizes.  Only used if *layout* is a string.
@@ -2349,6 +2353,8 @@ def set_layout_engine(self, layout=None, **kwargs):
             new_layout_engine = TightLayoutEngine(**kwargs)
         elif layout == 'constrained':
             new_layout_engine = ConstrainedLayoutEngine(**kwargs)
+        elif layout == 'none':
+            new_layout_engine = None
         elif isinstance(layout, LayoutEngine):
             new_layout_engine = layout
         else:
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -620,6 +620,9 @@ def test_invalid_layouts():
     with pytest.raises(RuntimeError, match='Colorbar layout of new layout'):
         fig.set_layout_engine("constrained")
 
+    fig.set_layout_engine("none")
+    assert fig.get_layout_engine() is None
+
 
 @check_figures_equal(extensions=["png", "pdf"])
 def test_add_artist(fig_test, fig_ref):
