Add a helper to generate xy coordinates for AxisArtistHelper.

anntzer · anntzer · commit 401da43e4567 · 2022-12-28T12:35:12.000Z
AxisArtistHelper can generate either x or y ticks/gridlines depending
on the value of self.nth_coord.  The implementation often requires
generating e.g. shape (2,) arrays such that the nth_coord column is
set to a tick position, and the 1-nth_coord column has is set to
0.  This is currently done using constructs like ``verts = [0, 0];
verts[self.nth_coord] = value`` where the mutation doesn't really help
legibility.  Instead, introduce a ``_to_xy`` helper that allows writing
``to_xy(variable=x, fixed=0)``.
diff --git a/doc/api/next_api_changes/deprecations/22314-AL.rst b/doc/api/next_api_changes/deprecations/22314-AL.rst
@@ -0,0 +1,3 @@
+``passthru_pt``
+~~~~~~~~~~~~~~~
+This attribute of ``AxisArtistHelper``\s is deprecated.
diff --git a/lib/mpl_toolkits/axisartist/axislines.py b/lib/mpl_toolkits/axisartist/axislines.py
@@ -95,38 +95,51 @@ def update_lim(self, axes):
         delta2 = _api.deprecated("3.6")(
             property(lambda self: 0.00001, lambda self, value: None))
 
+        def _to_xy(self, values, const):
+            """
+            Create a (len(values), 2)-shape array representing (x, y) pairs.
+
+            *values* go into the coordinate determined by ``self.nth_coord``.
+            The other coordinate is filled with the constant *const*.
+
+            Example::
+
+                >>> self.nth_coord = 0
+                >>> self._to_xy([1, 2, 3], const=0)
+                array([[1, 0],
+                       [2, 0],
+                       [3, 0]])
+            """
+            if self.nth_coord == 0:
+                return np.stack(np.broadcast_arrays(values, const), axis=-1)
+            elif self.nth_coord == 1:
+                return np.stack(np.broadcast_arrays(const, values), axis=-1)
+            else:
+                raise ValueError("Unexpected nth_coord")
+
     class Fixed(_Base):
         """Helper class for a fixed (in the axes coordinate) axis."""
 
+        # deprecated with passthru_pt
         _default_passthru_pt = dict(left=(0, 0),
                                     right=(1, 0),
                                     bottom=(0, 0),
                                     top=(0, 1))
+        passthru_pt = _api.deprecated("3.7")(property(
+            lambda self: self._default_passthru_pt[self._loc]))
 
         def __init__(self, loc, nth_coord=None):
             """``nth_coord = 0``: x-axis; ``nth_coord = 1``: y-axis."""
             _api.check_in_list(["left", "right", "bottom", "top"], loc=loc)
             self._loc = loc
-
-            if nth_coord is None:
-                if loc in ["left", "right"]:
-                    nth_coord = 1
-                else:  # "bottom", "top"
-                    nth_coord = 0
-
-            self.nth_coord = nth_coord
-
+            self._pos = _api.check_getitem(
+                {"bottom": 0, "top": 1, "left": 0, "right": 1}, loc=loc)
+            self.nth_coord = (
+                nth_coord if nth_coord is not None else
+                {"bottom": 0, "top": 0, "left": 1, "right": 1}[loc])
             super().__init__()
-
-            self.passthru_pt = self._default_passthru_pt[loc]
-
-            _verts = np.array([[0., 0.],
-                               [1., 1.]])
-            fixed_coord = 1 - nth_coord
-            _verts[:, fixed_coord] = self.passthru_pt[fixed_coord]
-
             # axis line in transAxes
-            self._path = Path(_verts)
+            self._path = Path(self._to_xy((0, 1), const=self._pos))
 
         def get_nth_coord(self):
             return self.nth_coord
@@ -209,8 +222,7 @@ def get_tick_iterators(self, axes):
 
             def _f(locs, labels):
                 for x, l in zip(locs, labels):
-                    c = list(self.passthru_pt)  # copy
-                    c[self.nth_coord] = x
+                    c = self._to_xy(x, const=self._pos)
                     # check if the tick point is inside axes
                     c2 = tick_to_axes.transform(c)
                     if mpl.transforms._interval_contains_close(
@@ -227,15 +239,10 @@ def __init__(self, axes, nth_coord,
             self.axis = [axes.xaxis, axes.yaxis][self.nth_coord]
 
         def get_line(self, axes):
-            _verts = np.array([[0., 0.],
-                               [1., 1.]])
-
             fixed_coord = 1 - self.nth_coord
             data_to_axes = axes.transData - axes.transAxes
             p = data_to_axes.transform([self._value, self._value])
-            _verts[:, fixed_coord] = p[fixed_coord]
-
-            return Path(_verts)
+            return Path(self._to_xy((0, 1), const=p[fixed_coord]))
 
         def get_line_transform(self, axes):
             return axes.transAxes
@@ -250,13 +257,12 @@ def get_axislabel_pos_angle(self, axes):
             get_label_transform() returns a transform of (transAxes+offset)
             """
             angle = [0, 90][self.nth_coord]
-            _verts = [0.5, 0.5]
             fixed_coord = 1 - self.nth_coord
             data_to_axes = axes.transData - axes.transAxes
             p = data_to_axes.transform([self._value, self._value])
-            _verts[fixed_coord] = p[fixed_coord]
-            if 0 <= _verts[fixed_coord] <= 1:
-                return _verts, angle
+            verts = self._to_xy(0.5, const=p[fixed_coord])
+            if 0 <= verts[fixed_coord] <= 1:
+                return verts, angle
             else:
                 return None, None
 
@@ -282,8 +288,7 @@ def get_tick_iterators(self, axes):
 
             def _f(locs, labels):
                 for x, l in zip(locs, labels):
-                    c = [self._value, self._value]
-                    c[self.nth_coord] = x
+                    c = self._to_xy(x, const=self._value)
                     c1, c2 = data_to_axes.transform(c)
                     if 0 <= c1 <= 1 and 0 <= c2 <= 1:
                         yield c, angle_normal, angle_tangent, l

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+``passthru_pt``
	`2`	`+~~~~~~~~~~~~~~~`
	`3`	+This attribute of ``AxisArtistHelper``\s is deprecated.