MNT: Remove cached renderer from figure

greglucas · greglucas · commit 333af74c875f · 2022-08-11T12:59:27.000-06:00
Let the canvas decide whether to cache the renderer or not and
request the renderer from the canvas. The canvas can either return
a cached version or a new one.
diff --git a/doc/api/next_api_changes/deprecations/23202-GL.rst b/doc/api/next_api_changes/deprecations/23202-GL.rst
@@ -0,0 +1,5 @@
+``Axes.get_renderer_cache``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The canvas now takes care of the renderer and whether to cache it
+or not. The alternative is to call ``axes.figure.canvas.get_renderer()``.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -3068,33 +3068,22 @@ def draw(self, renderer):
     def draw_artist(self, a):
         """
         Efficiently redraw a single artist.
-
-        This method can only be used after an initial draw of the figure,
-        because that creates and caches the renderer needed here.
         """
-        if self.figure._cachedRenderer is None:
-            raise AttributeError("draw_artist can only be used after an "
-                                 "initial draw which caches the renderer")
-        a.draw(self.figure._cachedRenderer)
+        a.draw(self.figure.canvas.get_renderer())
 
     def redraw_in_frame(self):
         """
         Efficiently redraw Axes data, but not axis ticks, labels, etc.
-
-        This method can only be used after an initial draw which caches the
-        renderer.
         """
-        if self.figure._cachedRenderer is None:
-            raise AttributeError("redraw_in_frame can only be used after an "
-                                 "initial draw which caches the renderer")
         with ExitStack() as stack:
             for artist in [*self._axis_map.values(),
                            self.title, self._left_title, self._right_title]:
                 stack.enter_context(artist._cm_set(visible=False))
-            self.draw(self.figure._cachedRenderer)
+            self.draw(self.figure.canvas.get_renderer())
 
+    @_api.deprecated("3.6", alternative="Axes.figure.canvas.get_renderer()")
     def get_renderer_cache(self):
-        return self.figure._cachedRenderer
+        return self.figure.canvas.get_renderer()
 
     # Axes rectangle characteristics
 
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1535,8 +1535,7 @@ def _mouse_handler(event):
 
 def _get_renderer(figure, print_method=None):
     """
-    Get the renderer that would be used to save a `.Figure`, and cache it on
-    the figure.
+    Get the renderer that would be used to save a `.Figure`.
 
     If you need a renderer without any active draw methods use
     renderer._draw_disabled to temporary patch them out at your call site.
@@ -1559,7 +1558,7 @@ def _draw(renderer): raise Done(renderer)
         try:
             print_method(io.BytesIO())
         except Done as exc:
-            renderer, = figure._cachedRenderer, = exc.args
+            renderer, = exc.args
             return renderer
         else:
             raise RuntimeError(f"{print_method} did not call Figure.draw, so "
diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -422,6 +422,9 @@ def _renderer(self):
             self._cached_renderer = RendererCairo(self.figure.dpi)
         return self._cached_renderer
 
+    def get_renderer(self):
+        return self._renderer
+
     def copy_from_bbox(self, bbox):
         surface = self._renderer.gc.ctx.get_target()
         if not isinstance(surface, cairo.ImageSurface):
diff --git a/lib/matplotlib/backends/backend_wx.py b/lib/matplotlib/backends/backend_wx.py
@@ -620,7 +620,7 @@ def gui_repaint(self, drawDC=None):
         # DC (see GraphicsContextWx._cache).
         bmp = (self.bitmap.ConvertToImage().ConvertToBitmap()
                if wx.Platform == '__WXMSW__'
-                  and isinstance(self.figure._cachedRenderer, RendererWx)
+                  and isinstance(self.figure.canvas.get_renderer(), RendererWx)
                else self.bitmap)
         drawDC.DrawBitmap(bmp, 0, 0)
         if self._rubberband_rect is not None:
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2253,7 +2253,6 @@ def axes(self):
 
     def draw(self, renderer):
         # docstring inherited
-        self._cachedRenderer = renderer
 
         # draw the figure bounding box, perhaps none for white figure
         if not self.get_visible():
@@ -2493,7 +2492,6 @@ def __init__(self,
 
         self._axstack = _AxesStack()  # track all figure axes and current axes
         self.clear()
-        self._cachedRenderer = None
 
         # list of child gridspecs for this figure
         self._gridspecs = []
@@ -2655,9 +2653,7 @@ def axes(self):
     get_axes = axes.fget
 
     def _get_renderer(self):
-        if self._cachedRenderer is not None:
-            return self._cachedRenderer
-        elif hasattr(self.canvas, 'get_renderer'):
+        if hasattr(self.canvas, 'get_renderer'):
             return self.canvas.get_renderer()
         else:
             return _get_renderer(self)
@@ -3051,7 +3047,6 @@ def clear(self, keep_observers=False):
     @allow_rasterization
     def draw(self, renderer):
         # docstring inherited
-        self._cachedRenderer = renderer
 
         # draw the figure bounding box, perhaps none for white figure
         if not self.get_visible():
@@ -3092,14 +3087,8 @@ def draw_without_rendering(self):
     def draw_artist(self, a):
         """
         Draw `.Artist` *a* only.
-
-        This method can only be used after an initial draw of the figure,
-        because that creates and caches the renderer needed here.
         """
-        if self._cachedRenderer is None:
-            raise AttributeError("draw_artist can only be used after an "
-                                 "initial draw which caches the renderer")
-        a.draw(self._cachedRenderer)
+        a.draw(self.canvas.get_renderer())
 
     def __getstate__(self):
         state = super().__getstate__()
@@ -3109,9 +3098,6 @@ def __getstate__(self):
         # re-attached to another.
         state.pop("canvas")
 
-        # Set cached renderer to None -- it can't be pickled.
-        state["_cachedRenderer"] = None
-
         # discard any changes to the dpi due to pixel ratio changes
         state["_dpi"] = state.get('_original_dpi', state['_dpi'])
 
diff --git a/lib/matplotlib/tests/test_backend_macosx.py b/lib/matplotlib/tests/test_backend_macosx.py
@@ -16,11 +16,11 @@ def test_cached_renderer():
     # a fig.canvas.draw() call
     fig = plt.figure(1)
     fig.canvas.draw()
-    assert fig._cachedRenderer is not None
+    assert fig.canvas.get_renderer()._renderer is not None
 
     fig = plt.figure(2)
     fig.draw_without_rendering()
-    assert fig._cachedRenderer is not None
+    assert fig.canvas.get_renderer()._renderer is not None
 
 
 @pytest.mark.backend('macosx')
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -984,7 +984,7 @@ def test_empty_imshow(make_norm):
     fig.canvas.draw()
 
     with pytest.raises(RuntimeError):
-        im.make_image(fig._cachedRenderer)
+        im.make_image(fig.canvas.get_renderer())
 
 
 def test_imshow_float16():
diff --git a/lib/mpl_toolkits/tests/test_axes_grid1.py b/lib/mpl_toolkits/tests/test_axes_grid1.py
@@ -552,7 +552,7 @@ def test_auto_adjustable():
     pad = 0.1
     make_axes_area_auto_adjustable(ax, pad=pad)
     fig.canvas.draw()
-    tbb = ax.get_tightbbox(fig._cachedRenderer)
+    tbb = ax.get_tightbbox()
     assert tbb.x0 == pytest.approx(pad * fig.dpi)
     assert tbb.x1 == pytest.approx(fig.bbox.width - pad * fig.dpi)
     assert tbb.y0 == pytest.approx(pad * fig.dpi)
