Set layout engine in _create_figure() instead of draw()

Only the figure creator should own the layout engine. Moving
set_layout_engine into _create_figure() ensures this — the existing
hasattr(self, "figure") guard prevents embedded plots/compositions
from setting it.

Author: has2k1

plotnine/composition/_compose.py

@@ -466,11 +466,13 @@ def _create_figure(self):
         import matplotlib.pyplot as plt
 
         from plotnine._mpl.gridspec import p9GridSpec
+        from plotnine._mpl.layout_manager import PlotnineLayoutEngine
 
         figure = plt.figure()
         self._generate_gridspecs(
             figure, p9GridSpec(1, 1, figure, nest_into=None)
         )
+        figure.set_layout_engine(PlotnineLayoutEngine(self))
 
     def _generate_gridspecs(self, figure: Figure, container_gs: p9GridSpec):
         from plotnine import ggplot
@@ -532,7 +534,6 @@ def draw(self, *, show: bool = False) -> Figure:
         :
             Matplotlib figure
         """
-        from .._mpl.layout_manager import PlotnineLayoutEngine
 
         def _draw(cmp):
             figure = cmp._setup()
@@ -557,7 +558,6 @@ def _draw(cmp):
             self._draw_annotation()
             self._draw_composition_background()
             self.theme.apply()
-            figure.set_layout_engine(PlotnineLayoutEngine(self))
 
         return figure
 

plotnine/ggplot.py

@@ -346,8 +346,6 @@ def draw(self, *, show: bool = False) -> Figure:
         :
             Matplotlib figure
         """
-        from ._mpl.layout_manager import PlotnineLayoutEngine
-
         with plot_context(self, show=show):
             figure = self._setup()
             self._build()
@@ -373,7 +371,6 @@ def draw(self, *, show: bool = False) -> Figure:
 
             # Artist object theming
             self.theme.apply()
-            figure.set_layout_engine(PlotnineLayoutEngine(self))
 
         return figure
 
@@ -395,9 +392,11 @@ def _create_figure(self):
         import matplotlib.pyplot as plt
 
         from ._mpl.gridspec import p9GridSpec
+        from ._mpl.layout_manager import PlotnineLayoutEngine
 
         self.figure = plt.figure()
         self._gridspec = p9GridSpec(1, 1, self.figure)
+        self.figure.set_layout_engine(PlotnineLayoutEngine(self))
 
     def _build(self):
         """