Define FloatingAxes boundary patch in data coordinates.

anntzer · anntzer · commit cc8df4f90754 · 2021-07-08T10:22:01.000+02:00
Currently, the boundary patch of FloatingAxes is drawn in "parent axes
data" (rectilinear) coordinates, using manual interpolation as defined
in get_boundary.

Instead, it can be defined in child axes data coordinates, and use
`helper_trf + transData` as transform, relying on interpolation
mechanisms already present in the transform machinery (for example, this
means that polar FloatingAxes benefit from the more-accurate
transforming of circular arcs).

Likewise, adjust_axes_lim can use normal path methods to get its
extents, rather than relying on manual interpolation.  This is the cause
of the baseline image tolerance change: in test_curvelinear3, for
example, we now have exactly `bbox.xmin = bbox.ymin = -10` and
`bbox.xmax = bbox.ymax = +10` rather than slightly different values
arising from interpolation and inaccurate transform composition.  (But
one can manually check that the changes are all just tiny shifts.)

(On the other hand, I'll likely further change these baselines in the
future, so let's not update the files right now.)
diff --git a/doc/api/next_api_changes/deprecations/20254-AL.rst b/doc/api/next_api_changes/deprecations/20254-AL.rst
@@ -0,0 +1,3 @@
+``floating_axes.GridHelperCurveLinear.get_boundary``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated, with no replacement.
diff --git a/lib/mpl_toolkits/axisartist/floating_axes.py b/lib/mpl_toolkits/axisartist/floating_axes.py
@@ -7,7 +7,7 @@
 
 import numpy as np
 
-from matplotlib import cbook
+from matplotlib import _api, cbook
 import matplotlib.patches as mpatches
 from matplotlib.path import Path
 import matplotlib.axes as maxes
@@ -287,6 +287,7 @@ def get_gridlines(self, which="major", axis="both"):
             grid_lines.extend(self._grid_info["lat_lines"])
         return grid_lines
 
+    @_api.deprecated("3.5")
     def get_boundary(self):
         """
         Return (N, 2) array of (x, y) coordinate of the boundary.
@@ -322,11 +323,19 @@ def __init__(self, *args, **kwargs):
 
     def _gen_axes_patch(self):
         # docstring inherited
-        return mpatches.Polygon(self.get_grid_helper().get_boundary())
+        # Using a public API to access _extremes.
+        (x0, _), (x1, _), (y0, _), (y1, _) = map(
+            self.get_grid_helper().get_data_boundary,
+            ["left", "right", "bottom", "top"])
+        patch = mpatches.Polygon([(x0, y0), (x1, y0), (x1, y1), (x0, y1)])
+        patch.get_path()._interpolation_steps = 100
+        return patch
 
     def cla(self):
         super().cla()
-        self.patch.set_transform(self.transData)
+        self.patch.set_transform(
+            self.get_grid_helper().grid_finder.get_transform()
+            + self.transData)
         # The original patch is not in the draw tree; it is only used for
         # clipping purposes.
         orig_patch = super()._gen_axes_patch()
@@ -336,18 +345,12 @@ def cla(self):
         self.gridlines.set_clip_path(orig_patch)
 
     def adjust_axes_lim(self):
-        grid_helper = self.get_grid_helper()
-        t = grid_helper.get_boundary()
-        x, y = t[:, 0], t[:, 1]
-
-        xmin, xmax = min(x), max(x)
-        ymin, ymax = min(y), max(y)
-
-        dx = (xmax-xmin) / 100
-        dy = (ymax-ymin) / 100
-
-        self.set_xlim(xmin-dx, xmax+dx)
-        self.set_ylim(ymin-dy, ymax+dy)
+        bbox = self.patch.get_path().get_extents(
+            # First transform to pixel coords, then to parent data coords.
+            self.patch.get_transform() - self.transData)
+        bbox = bbox.expanded(1.02, 1.02)
+        self.set_xlim(bbox.xmin, bbox.xmax)
+        self.set_ylim(bbox.ymin, bbox.ymax)
 
 
 floatingaxes_class_factory = cbook._make_class_factory(
diff --git a/lib/mpl_toolkits/tests/test_axisartist_floating_axes.py b/lib/mpl_toolkits/tests/test_axisartist_floating_axes.py
@@ -18,7 +18,9 @@ def test_subplot():
     fig.add_subplot(ax)
 
 
-@image_comparison(['curvelinear3.png'], style='default', tol=0.01)
+# Rather high tolerance to allow ongoing work with floating axes internals;
+# remove when image is regenerated.
+@image_comparison(['curvelinear3.png'], style='default', tol=5)
 def test_curvelinear3():
     fig = plt.figure(figsize=(5, 5))
 
@@ -72,7 +74,9 @@ def test_curvelinear3():
     l.set_clip_path(ax1.patch)
 
 
-@image_comparison(['curvelinear4.png'], style='default', tol=0.015)
+# Rather high tolerance to allow ongoing work with floating axes internals;
+# remove when image is regenerated.
+@image_comparison(['curvelinear4.png'], style='default', tol=0.9)
 def test_curvelinear4():
     # Remove this line when this test image is regenerated.
     plt.rcParams['text.kerning_factor'] = 6

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+``floating_axes.GridHelperCurveLinear.get_boundary``
	`2`	`+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`
	`3`	`+... is deprecated, with no replacement.`