Backport PR #17560: FIX: do not let no-op monkey patches to renderer leak out

QuLogic · tacaswell · commit e40d9afa88d1 · 2020-06-09T22:33:42.000-04:00
Merge pull request #17560 from tacaswell/fix_noop_tight_bbox FIX: do not let no-op monkey patches to renderer leak out Conflicts: lib/matplotlib/backend_bases.py - trivial conflicting imports - did not back port other changes to tight box lib/matplotlib/tight_layout.py - ended up not backporting any of the changes
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -32,7 +32,7 @@
     The base class for the messaging area.
 """
 
-from contextlib import contextmanager
+from contextlib import contextmanager, suppress
 from enum import IntEnum
 import functools
 import importlib
@@ -52,6 +52,7 @@
 from matplotlib._pylab_helpers import Gcf
 from matplotlib.transforms import Affine2D
 from matplotlib.path import Path
+from matplotlib.cbook import _setattr_cm
 
 try:
     from PIL import __version__ as PILLOW_VERSION
@@ -712,6 +713,23 @@ def stop_filter(self, filter_func):
         Currently only supported by the agg renderer.
         """
 
+    def _draw_disabled(self):
+        """
+        Context manager to temporary disable drawing.
+
+        This is used for getting the drawn size of Artists.  This lets us
+        run the draw process to update any Python state but does not pay the
+        cost of the draw_XYZ calls on the canvas.
+        """
+        no_ops = {
+            meth_name: lambda *args, **kwargs: None
+            for meth_name in dir(RendererBase)
+            if (meth_name.startswith("draw_")
+                or meth_name in ["open_group", "close_group"])
+        }
+
+        return _setattr_cm(self, **no_ops)
+
 
 class GraphicsContextBase:
     """An abstract base class that provides color, line styles, etc."""
@@ -1520,15 +1538,14 @@ def __init__(self, name, canvas, key, x=0, y=0, guiEvent=None):
         LocationEvent.__init__(self, name, canvas, x, y, guiEvent=guiEvent)
 
 
-def _get_renderer(figure, print_method, *, draw_disabled=False):
+def _get_renderer(figure, print_method):
     """
     Get the renderer that would be used to save a `~.Figure`, and cache it on
     the figure.
 
-    If *draw_disabled* is True, additionally replace drawing methods on
-    *renderer* by no-ops.  This is used by the tight-bbox-saving renderer,
-    which needs to walk through the artist tree to compute the tight-bbox, but
-    for which the output file may be closed early.
+    If you need a renderer without any active draw methods use
+    renderer._draw_disabled to temporary patch them out at your call site.
+
     """
     # This is implemented by triggering a draw, then immediately jumping out of
     # Figure.draw() by raising an exception.
@@ -1544,12 +1561,6 @@ def _draw(renderer): raise Done(renderer)
         except Done as exc:
             renderer, = figure._cachedRenderer, = exc.args
 
-    if draw_disabled:
-        for meth_name in dir(RendererBase):
-            if (meth_name.startswith("draw_")
-                    or meth_name in ["open_group", "close_group"]):
-                setattr(renderer, meth_name, lambda *args, **kwargs: None)
-
     return renderer
 
 
@@ -2080,8 +2091,11 @@ def print_figure(self, filename, dpi=None, facecolor=None, edgecolor=None,
                         self.figure,
                         functools.partial(
                             print_method, dpi=dpi, orientation=orientation),
-                        draw_disabled=True)
-                    self.figure.draw(renderer)
+                    ctx = (renderer._draw_disabled()
+                           if hasattr(renderer, '_draw_disabled')
+                           else suppress())
+                    with ctx:
+                        self.figure.draw(renderer)
                     bbox_artists = kwargs.pop("bbox_extra_artists", None)
                     bbox_inches = self.figure.get_tightbbox(renderer,
                             bbox_extra_artists=bbox_artists)
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2478,7 +2478,7 @@ def tight_layout(self, renderer=None, pad=1.08, h_pad=None, w_pad=None,
 
         from .tight_layout import (
             get_renderer, get_subplotspec_list, get_tight_layout_figure)
-
+        from contextlib import suppress
         subplotspec_list = get_subplotspec_list(self.axes)
         if None in subplotspec_list:
             cbook._warn_external("This figure includes Axes that are not "
@@ -2487,10 +2487,13 @@ def tight_layout(self, renderer=None, pad=1.08, h_pad=None, w_pad=None,
 
         if renderer is None:
             renderer = get_renderer(self)
-
-        kwargs = get_tight_layout_figure(
-            self, self.axes, subplotspec_list, renderer,
-            pad=pad, h_pad=h_pad, w_pad=w_pad, rect=rect)
+        ctx = (renderer._draw_disabled()
+               if hasattr(renderer, '_draw_disabled')
+               else suppress())
+        with ctx:
+            kwargs = get_tight_layout_figure(
+                self, self.axes, subplotspec_list, renderer,
+                pad=pad, h_pad=h_pad, w_pad=w_pad, rect=rect)
         if kwargs:
             self.subplots_adjust(**kwargs)
 
diff --git a/lib/matplotlib/tests/test_bbox_tight.py b/lib/matplotlib/tests/test_bbox_tight.py
@@ -108,3 +108,26 @@ def test_tight_pcolorfast():
     # Previously, the bbox would include the area of the image clipped out by
     # the axes, resulting in a very tall image given the y limits of (0, 0.1).
     assert width > height
+
+
+def test_noop_tight_bbox():
+    from PIL import Image
+    x_size, y_size = (10, 7)
+    dpi = 100
+    # make the figure just the right size up front
+    fig = plt.figure(frameon=False, dpi=dpi, figsize=(x_size/dpi, y_size/dpi))
+    ax = plt.Axes(fig, [0., 0., 1., 1.])
+    fig.add_axes(ax)
+    ax.set_axis_off()
+    ax.get_xaxis().set_visible(False)
+    ax.get_yaxis().set_visible(False)
+
+    data = np.arange(x_size * y_size).reshape(y_size, x_size)
+    ax.imshow(data)
+    out = BytesIO()
+    fig.savefig(out, bbox_inches='tight', pad_inches=0)
+    out.seek(0)
+    im = np.asarray(Image.open(out))
+    assert (im[:, :, 3] == 255).all()
+    assert not (im[:, :, :3] == 255).all()
+    assert im.shape == (7, 10, 4)
