Remove idiosyncratic get_tick_iterator API.

It's only ever used essentially to expose GridHelperCurveLinear._grid_info
to FixedAxisArtistHelper.get_tick_iterators; it seems better to access
it from the sole caller.  (Note that floating_axes already does the same
direct access to the private _grid_info.)

Removing get_tick_iterator also removes the confusion with
get_tick_iterators (plural), which is a common API in axisartist.
Also note that the "minor" parameter of get_tick_iterator had a rather
peculiar meaning (it only switched the labels off).

Author: anntzer

doc/api/next_api_changes/deprecations/27300-AL.rst

@@ -0,0 +1,3 @@
+``GridHelperCurveLinear.get_tick_iterator``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated with no replacement.

lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py

@@ -3,7 +3,6 @@
 """
 
 import functools
-from itertools import chain
 
 import numpy as np
 
@@ -76,10 +75,18 @@ def get_tick_iterators(self, axes):
                     "top": "bottom", "bottom": "top"}[self.side]
         else:
             side = self.side
-        g = self.grid_helper
-        ti1 = g.get_tick_iterator(self.nth_coord_ticks, side)
-        ti2 = g.get_tick_iterator(1-self.nth_coord_ticks, side, minor=True)
-        return chain(ti1, ti2), iter([])
+
+        angle_tangent = dict(left=90, right=90, bottom=0, top=0)[side]
+
+        def iter_major():
+            for nth_coord, show_labels in [
+                    (self.nth_coord_ticks, True), (1 - self.nth_coord_ticks, False)]:
+                gi = self.grid_helper._grid_info[["lon", "lat"][nth_coord]]
+                for (xy, angle_normal), l in zip(
+                        gi["tick_locs"][side], gi["tick_labels"][side]):
+                    yield xy, angle_normal, angle_tangent, (l if show_labels else "")
+
+        return iter_major(), iter([])
 
 
 class FloatingAxisArtistHelper(_FloatingAxisArtistHelperBase):
@@ -211,14 +218,14 @@ def trf_xy(x, y):
         in_01 = functools.partial(
             mpl.transforms._interval_contains_close, (0, 1))
 
-        def f1():
+        def iter_major():
             for x, y, normal, tangent, lab \
                     in zip(xx1, yy1, angle_normal, angle_tangent, labels):
                 c2 = tick_to_axes.transform((x, y))
                 if in_01(c2[0]) and in_01(c2[1]):
                     yield [x, y], *np.rad2deg([normal, tangent]), lab
 
-        return f1(), iter([])
+        return iter_major(), iter([])
 
     def get_line_transform(self, axes):
         return axes.transData
@@ -309,6 +316,7 @@ def get_gridlines(self, which="major", axis="both"):
                 grid_lines.extend(gl)
         return grid_lines
 
+    @_api.deprecated("3.9")
     def get_tick_iterator(self, nth_coord, axis_side, minor=False):
         angle_tangent = dict(left=90, right=90, bottom=0, top=0)[axis_side]
         lon_or_lat = ["lon", "lat"][nth_coord]