Merge pull request matplotlib#28468 from meeseeksmachine/auto-backpor…

…t-of-pr-28465-on-v3.9.x

Backport PR matplotlib#28465 on branch v3.9.x (Fix pickling of SubFigures)

lib/matplotlib/figure.py

@@ -2224,7 +2224,6 @@ def __init__(self, parent, subplotspec, *,
         self.subplotpars = parent.subplotpars
         self.dpi_scale_trans = parent.dpi_scale_trans
         self._axobservers = parent._axobservers
-        self.canvas = parent.canvas
         self.transFigure = parent.transFigure
         self.bbox_relative = Bbox.null()
         self._redo_transform_rel_fig()
@@ -2241,6 +2240,10 @@ def __init__(self, parent, subplotspec, *,
         self._set_artist_props(self.patch)
         self.patch.set_antialiased(False)
 
+    @property
+    def canvas(self):
+        return self._parent.canvas
+
     @property
     def dpi(self):
         return self._parent.dpi

lib/matplotlib/figure.pyi

@@ -263,7 +263,6 @@ class SubFigure(FigureBase):
     figure: Figure
     subplotpars: SubplotParams
     dpi_scale_trans: Affine2D
-    canvas: FigureCanvasBase
     transFigure: Transform
     bbox_relative: Bbox
     figbbox: BboxBase
@@ -282,6 +281,8 @@ class SubFigure(FigureBase):
         **kwargs
     ) -> None: ...
     @property
+    def canvas(self) -> FigureCanvasBase: ...
+    @property
     def dpi(self) -> float: ...
     @dpi.setter
     def dpi(self, value: float) -> None: ...

lib/matplotlib/tests/test_pickle.py

@@ -93,6 +93,11 @@ def _generate_complete_test_figure(fig_ref):
     plt.errorbar(x, x * -0.5, xerr=0.2, yerr=0.4, label='$-.5 x$')
     plt.legend(draggable=True)
 
+    # Ensure subfigure parenting works.
+    subfigs = fig_ref.subfigures(2)
+    subfigs[0].subplots(1, 2)
+    subfigs[1].subplots(1, 2)
+
     fig_ref.align_ylabels()  # Test handling of _align_label_groups Groupers.