matplotlib · QuLogic · Jan 3, 2024 · Jan 1, 2023 · Jan 8, 2023 · Jan 8, 2023
diff --git a/doc/api/next_api_changes/deprecations/24834-DS.rst b/doc/api/next_api_changes/deprecations/24834-DS.rst
@@ -0,0 +1,17 @@
+Applying theta transforms in ``PolarTransform``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Applying theta transforms in `~matplotlib.projections.polar.PolarTransform`
+and `~matplotlib.projections.polar.InvertedPolarTransform`
+is deprecated, and will be removed in a future version of Matplotlib. This
+is currently the default behaviour when these transforms are used externally,
+but only takes affect when:
+
+- An axis is associated with the transform.
+- The axis has a non-zero theta offset or has theta values increasing in
+  a clockwise direction.
+
+To silence this warning and adopt future behaviour,
+set ``apply_theta_transforms=False``. If you need to retain the behaviour
+where theta values are transformed, chain the ``PolarTransform`` with
+a `~matplotlib.transforms.Affine2D` transform that performs the theta shift
+and/or sign shift.
diff --git a/galleries/examples/axisartist/demo_axis_direction.py b/galleries/examples/axisartist/demo_axis_direction.py
@@ -20,7 +20,10 @@ def setup_axes(fig, rect):
     """Polar projection, but in a rectangular box."""
     # see demo_curvelinear_grid.py for details
     grid_helper = GridHelperCurveLinear(
-        Affine2D().scale(np.pi/180., 1.) + PolarAxes.PolarTransform(),
+        (
+            Affine2D().scale(np.pi/180., 1.) +
+            PolarAxes.PolarTransform(apply_theta_transforms=False)
+        ),
         extreme_finder=angle_helper.ExtremeFinderCycle(
             20, 20,
             lon_cycle=360, lat_cycle=None,

diff --git a/galleries/examples/axisartist/demo_curvelinear_grid.py b/galleries/examples/axisartist/demo_curvelinear_grid.py
@@ -54,7 +54,8 @@ def curvelinear_test2(fig):
 
     # PolarAxes.PolarTransform takes radian. However, we want our coordinate
     # system in degree
-    tr = Affine2D().scale(np.pi/180, 1) + PolarAxes.PolarTransform()
+    tr = Affine2D().scale(np.pi/180, 1) + PolarAxes.PolarTransform(
+        apply_theta_transforms=False)
     # Polar projection, which involves cycle, and also has limits in
     # its coordinates, needs a special method to find the extremes
     # (min, max of the coordinate within the view).

diff --git a/galleries/examples/axisartist/demo_floating_axes.py b/galleries/examples/axisartist/demo_floating_axes.py
@@ -54,7 +54,7 @@ def setup_axes2(fig, rect):
     With custom locator and formatter.
     Note that the extreme values are swapped.
     """
-    tr = PolarAxes.PolarTransform()
+    tr = PolarAxes.PolarTransform(apply_theta_transforms=False)
 
     pi = np.pi
     angle_ticks = [(0, r"$0$"),
@@ -99,7 +99,8 @@ def setup_axes3(fig, rect):
     # scale degree to radians
     tr_scale = Affine2D().scale(np.pi/180., 1.)
 
-    tr = tr_rotate + tr_scale + PolarAxes.PolarTransform()
+    tr = tr_rotate + tr_scale + PolarAxes.PolarTransform(
+        apply_theta_transforms=False)
 
     grid_locator1 = angle_helper.LocatorHMS(4)
     tick_formatter1 = angle_helper.FormatterHMS()

diff --git a/galleries/examples/axisartist/demo_floating_axis.py b/galleries/examples/axisartist/demo_floating_axis.py
@@ -22,7 +22,8 @@
 def curvelinear_test2(fig):
     """Polar projection, but in a rectangular box."""
     # see demo_curvelinear_grid.py for details
-    tr = Affine2D().scale(np.pi / 180., 1.) + PolarAxes.PolarTransform()
+    tr = Affine2D().scale(np.pi / 180., 1.) + PolarAxes.PolarTransform(
+        apply_theta_transforms=False)
 
     extreme_finder = angle_helper.ExtremeFinderCycle(20,
                                                      20,

diff --git a/galleries/examples/axisartist/simple_axis_pad.py b/galleries/examples/axisartist/simple_axis_pad.py
@@ -21,7 +21,8 @@ def setup_axes(fig, rect):
     """Polar projection, but in a rectangular box."""
 
     # see demo_curvelinear_grid.py for details
-    tr = Affine2D().scale(np.pi/180., 1.) + PolarAxes.PolarTransform()
+    tr = Affine2D().scale(np.pi/180., 1.) + PolarAxes.PolarTransform(
+        apply_theta_transforms=False)
 
     extreme_finder = angle_helper.ExtremeFinderCycle(20, 20,
                                                      lon_cycle=360,

diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -15,6 +15,20 @@
 from matplotlib.spines import Spine
 
 
+def _apply_theta_transforms_warn():
+    _api.warn_deprecated(
+                "3.9",
+                message=(
+                    "Passing `apply_theta_transforms=True` (the default) "
+                    "is deprecated since Matplotlib %(since)s. "
+                    "Support for this will be removed in Matplotlib %(removal)s. "
+                    "To prevent this warning, set `apply_theta_transforms=False`, "
+                    "and make sure to shift theta values before being passed to "
+                    "this transform."
+                )
+            )
+
+
 class PolarTransform(mtransforms.Transform):
     r"""
     The base polar transform.
@@ -34,8 +48,8 @@ class PolarTransform(mtransforms.Transform):
 
     input_dims = output_dims = 2
 
-    def __init__(self, axis=None, use_rmin=True,
-                 _apply_theta_transforms=True, *, scale_transform=None):
+    def __init__(self, axis=None, use_rmin=True, *,
+                 apply_theta_transforms=True, scale_transform=None):
         """
         Parameters
         ----------
@@ -50,13 +64,15 @@ def __init__(self, axis=None, use_rmin=True,
         super().__init__()
         self._axis = axis
         self._use_rmin = use_rmin
-        self._apply_theta_transforms = _apply_theta_transforms
+        self._apply_theta_transforms = apply_theta_transforms
         self._scale_transform = scale_transform
+        if apply_theta_transforms:
+            _apply_theta_transforms_warn()
 
     __str__ = mtransforms._make_str_method(
         "_axis",
         use_rmin="_use_rmin",
-        _apply_theta_transforms="_apply_theta_transforms")
+        apply_theta_transforms="_apply_theta_transforms")
 
     def _get_rorigin(self):
         # Get lower r limit after being scaled by the radial scale transform
@@ -133,8 +149,10 @@ def transform_path_non_affine(self, path):
 
     def inverted(self):
         # docstring inherited
-        return PolarAxes.InvertedPolarTransform(self._axis, self._use_rmin,
-                                                self._apply_theta_transforms)
+        return PolarAxes.InvertedPolarTransform(
+            self._axis, self._use_rmin,
+            apply_theta_transforms=self._apply_theta_transforms
+        )
 
 
 class PolarAffine(mtransforms.Affine2DBase):
@@ -193,7 +211,7 @@ class InvertedPolarTransform(mtransforms.Transform):
     input_dims = output_dims = 2
 
     def __init__(self, axis=None, use_rmin=True,
-                 _apply_theta_transforms=True):
+                 *, apply_theta_transforms=True):
         """
         Parameters
         ----------
@@ -208,12 +226,14 @@ def __init__(self, axis=None, use_rmin=True,
         super().__init__()
         self._axis = axis
         self._use_rmin = use_rmin
-        self._apply_theta_transforms = _apply_theta_transforms
+        self._apply_theta_transforms = apply_theta_transforms
+        if apply_theta_transforms:
+            _apply_theta_transforms_warn()
 
     __str__ = mtransforms._make_str_method(
         "_axis",
         use_rmin="_use_rmin",
-        _apply_theta_transforms="_apply_theta_transforms")
+        apply_theta_transforms="_apply_theta_transforms")
 
     @_api.rename_parameter("3.8", "xy", "values")
     def transform_non_affine(self, values):
@@ -234,8 +254,10 @@ def transform_non_affine(self, values):
 
     def inverted(self):
         # docstring inherited
-        return PolarAxes.PolarTransform(self._axis, self._use_rmin,
-                                        self._apply_theta_transforms)
+        return PolarAxes.PolarTransform(
+            self._axis, self._use_rmin,
+            apply_theta_transforms=self._apply_theta_transforms
+        )
 
 
 class ThetaFormatter(mticker.Formatter):
@@ -879,7 +901,7 @@ def _set_lim_and_transforms(self):
         # data.  This one is aware of rmin
         self.transProjection = self.PolarTransform(
             self,
-            _apply_theta_transforms=False,
+            apply_theta_transforms=False,
             scale_transform=self.transScale
         )
         # Add dependency on rorigin.

diff --git a/lib/matplotlib/projections/polar.pyi b/lib/matplotlib/projections/polar.pyi
@@ -17,8 +17,8 @@ class PolarTransform(mtransforms.Transform):
         self,
         axis: PolarAxes | None = ...,
         use_rmin: bool = ...,
-        _apply_theta_transforms: bool = ...,
         *,
+        apply_theta_transforms: bool = ...,
         scale_transform: mtransforms.Transform | None = ...,
     ) -> None: ...
     def inverted(self) -> InvertedPolarTransform: ...
@@ -35,7 +35,8 @@ class InvertedPolarTransform(mtransforms.Transform):
         self,
         axis: PolarAxes | None = ...,
         use_rmin: bool = ...,
-        _apply_theta_transforms: bool = ...,
+        *,
+        apply_theta_transforms: bool = ...,
     ) -> None: ...
     def inverted(self) -> PolarTransform: ...
 

diff --git a/lib/matplotlib/tests/test_transforms.py b/lib/matplotlib/tests/test_transforms.py
@@ -859,7 +859,7 @@ def test_str_transform():
         PolarTransform(
             PolarAxes(0.125,0.1;0.775x0.8),
             use_rmin=True,
-            _apply_theta_transforms=False)),
+            apply_theta_transforms=False)),
     CompositeGenericTransform(
         CompositeGenericTransform(
             PolarAffine(

diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -1497,7 +1497,7 @@ def _get_xy_transform(self, renderer, coords):
             return self.axes.transData
         elif coords == 'polar':
             from matplotlib.projections import PolarAxes
-            tr = PolarAxes.PolarTransform()
+            tr = PolarAxes.PolarTransform(apply_theta_transforms=False)
             trans = tr + self.axes.transData
             return trans
 

diff --git a/lib/mpl_toolkits/axisartist/tests/test_floating_axes.py b/lib/mpl_toolkits/axisartist/tests/test_floating_axes.py
@@ -24,7 +24,7 @@ def test_curvelinear3():
     fig = plt.figure(figsize=(5, 5))
 
     tr = (mtransforms.Affine2D().scale(np.pi / 180, 1) +
-          mprojections.PolarAxes.PolarTransform())
+          mprojections.PolarAxes.PolarTransform(apply_theta_transforms=False))
     grid_helper = GridHelperCurveLinear(
         tr,
         extremes=(0, 360, 10, 3),
@@ -73,7 +73,7 @@ def test_curvelinear4():
     fig = plt.figure(figsize=(5, 5))
 
     tr = (mtransforms.Affine2D().scale(np.pi / 180, 1) +
-          mprojections.PolarAxes.PolarTransform())
+          mprojections.PolarAxes.PolarTransform(apply_theta_transforms=False))
     grid_helper = GridHelperCurveLinear(
         tr,
         extremes=(120, 30, 10, 0),

diff --git a/lib/mpl_toolkits/axisartist/tests/test_grid_helper_curvelinear.py b/lib/mpl_toolkits/axisartist/tests/test_grid_helper_curvelinear.py
@@ -82,7 +82,8 @@ def test_polar_box():
 
     # PolarAxes.PolarTransform takes radian. However, we want our coordinate
     # system in degree
-    tr = Affine2D().scale(np.pi / 180., 1.) + PolarAxes.PolarTransform()
+    tr = (Affine2D().scale(np.pi / 180., 1.) +
+          PolarAxes.PolarTransform(apply_theta_transforms=False))
 
     # polar projection, which involves cycle, and also has limits in
     # its coordinates, needs a special method to find the extremes
@@ -144,7 +145,8 @@ def test_axis_direction():
 
     # PolarAxes.PolarTransform takes radian. However, we want our coordinate
     # system in degree
-    tr = Affine2D().scale(np.pi / 180., 1.) + PolarAxes.PolarTransform()
+    tr = (Affine2D().scale(np.pi / 180., 1.) +
+          PolarAxes.PolarTransform(apply_theta_transforms=False))
 
     # polar projection, which involves cycle, and also has limits in
     # its coordinates, needs a special method to find the extremes