matplotlib · timhoffm · Dec 7, 2021 · Aug 15, 2021 · Aug 15, 2021 · Nov 15, 2021
diff --git a/doc/api/next_api_changes/deprecations/20839-EP.rst b/doc/api/next_api_changes/deprecations/20839-EP.rst
@@ -0,0 +1,4 @@
+Selector widget state internals
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The *state_modifier_keys* attribute have been privatized and the modifier keys
+needs to be set when creating the widget.
diff --git a/doc/users/next_whats_new/rectangle_patch_rotation.rst b/doc/users/next_whats_new/rectangle_patch_rotation.rst
@@ -0,0 +1,5 @@
+Rectangle patch rotation point
+------------------------------
+
+The rotation point of the `~matplotlib.patches.Rectangle` can now be set to 'xy',
+'center' or a 2-tuple of numbers.
diff --git a/doc/users/next_whats_new/selector_improvement.rst b/doc/users/next_whats_new/selector_improvement.rst
@@ -0,0 +1,40 @@
+Selectors improvement: rotation, aspect ratio correction and add/remove state
+-----------------------------------------------------------------------------
+
+The `~matplotlib.widgets.RectangleSelector` and
+`~matplotlib.widgets.EllipseSelector` can now be rotated interactively between
+-45° and 45°. The range limits are currently dictated by the implementation.
+The rotation is enabled or disabled by striking the *r* key
+('r' is the default key mapped to 'rotate' in *state_modifier_keys*) or by calling
+``selector.add_state('rotate')``.
+
+The aspect ratio of the axes can now be taken into account when using the
+"square" state. This is enabled by specifying ``use_data_coordinates='True'`` when
+the selector is initialized.
+
+In addition to changing selector state interactively using the modifier keys
+defined in *state_modifier_keys*, the selector state can now be changed
+programmatically using the *add_state* and *remove_state* methods.
+
+
+.. code-block:: python
+
+    import matplotlib.pyplot as plt
+    from matplotlib.widgets import RectangleSelector
+    import numpy as np
+
+    values = np.arange(0, 100)
+
+    fig = plt.figure()
+    ax = fig.add_subplot()
+    ax.plot(values, values)
+
+    selector = RectangleSelector(ax, print, interactive=True,
+                                 drag_from_anywhere=True,
+                                 use_data_coordinates=True)
+    selector.add_state('rotate') # alternatively press 'r' key
+    # rotate the selector interactively
+
+    selector.remove_state('rotate') # alternatively press 'r' key
+
+    selector.add_state('square')
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -8094,3 +8094,13 @@ def violin(self, vpstats, positions=None, vert=True, widths=0.5,
     tricontourf = mtri.tricontourf
     tripcolor = mtri.tripcolor
     triplot = mtri.triplot
+
+    def _get_aspect_ratio(self):
+        """
+        Convenience method to calculate the aspect ratio of the axes in
+        the display coordinate system.
+        """
+        figure_size = self.get_figure().get_size_inches()
+        ll, ur = self.get_position() * figure_size
+        width, height = ur - ll
+        return height / (width * self.get_data_ratio())
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -706,7 +706,8 @@ def __str__(self):
         return fmt % pars
 
     @docstring.dedent_interpd
-    def __init__(self, xy, width, height, angle=0.0, **kwargs):
+    def __init__(self, xy, width, height, angle=0.0, *,
+                 rotation_point='xy', **kwargs):
         """
         Parameters
         ----------
@@ -717,7 +718,11 @@ def __init__(self, xy, width, height, angle=0.0, **kwargs):
         height : float
             Rectangle height.
         angle : float, default: 0
-            Rotation in degrees anti-clockwise about *xy*.
+            Rotation in degrees anti-clockwise about the rotation point.
+        rotation_point : {'xy', 'center', (number, number)}, default: 'xy'
+            If ``'xy'``, rotate around the anchor point. If ``'center'`` rotate
+            around the center. If 2-tuple of number, rotate around this
+            coordinate.
 
         Other Parameters
         ----------------
@@ -730,6 +735,14 @@ def __init__(self, xy, width, height, angle=0.0, **kwargs):
         self._width = width
         self._height = height
         self.angle = float(angle)
+        self.rotation_point = rotation_point
+        # Required for RectangleSelector with axes aspect ratio != 1
+        # The patch is defined in data coordinates and when changing the
+        # selector with square modifier and not in data coordinates, we need
+        # to correct for the aspect ratio difference between the data and
+        # display coordinate systems. Its value is typically provide by
+        # Axes._get_aspect_ratio()
+        self._aspect_ratio_correction = 1.0
         self._convert_units()  # Validate the inputs.
 
     def get_path(self):
@@ -750,9 +763,36 @@ def get_patch_transform(self):
         # important to call the accessor method and not directly access the
         # transformation member variable.
         bbox = self.get_bbox()
-        return (transforms.BboxTransformTo(bbox)
-                + transforms.Affine2D().rotate_deg_around(
-                    bbox.x0, bbox.y0, self.angle))
+        if self.rotation_point == 'center':
+            width, height = bbox.x1 - bbox.x0, bbox.y1 - bbox.y0
+            rotation_point = bbox.x0 + width / 2., bbox.y0 + height / 2.
+        elif self.rotation_point == 'xy':
+            rotation_point = bbox.x0, bbox.y0
+        else:
+            rotation_point = self.rotation_point
+        return transforms.BboxTransformTo(bbox) \
+                + transforms.Affine2D() \
+                .translate(-rotation_point[0], -rotation_point[1]) \
+                .scale(1, self._aspect_ratio_correction) \
+                .rotate_deg(self.angle) \
+                .scale(1, 1 / self._aspect_ratio_correction) \
+                .translate(*rotation_point)
+
+    @property
+    def rotation_point(self):
+        """The rotation point of the patch."""
+        return self._rotation_point
+
+    @rotation_point.setter
+    def rotation_point(self, value):
+        if value in ['center', 'xy'] or (
+                isinstance(value, tuple) and len(value) == 2 and
+                isinstance(value[0], Number) and isinstance(value[1], Number)
+                ):
+            self._rotation_point = value
+        else:
+            raise ValueError("`rotation_point` must be one of "
+                             "{'xy', 'center', (number, number)}.")
 
     def get_x(self):
         """Return the left coordinate of the rectangle."""
@@ -1511,6 +1551,12 @@ def __init__(self, xy, width, height, angle=0, **kwargs):
         self._width, self._height = width, height
         self._angle = angle
         self._path = Path.unit_circle()
+        # Required for EllipseSelector with axes aspect ratio != 1
+        # The patch is defined in data coordinates and when changing the
+        # selector with square modifier and not in data coordinates, we need
+        # to correct for the aspect ratio difference between the data and
+        # display coordinate systems.
+        self._aspect_ratio_correction = 1.0
         # Note: This cannot be calculated until this is added to an Axes
         self._patch_transform = transforms.IdentityTransform()
 
@@ -1528,8 +1574,9 @@ def _recompute_transform(self):
         width = self.convert_xunits(self._width)
         height = self.convert_yunits(self._height)
         self._patch_transform = transforms.Affine2D() \
-            .scale(width * 0.5, height * 0.5) \
+            .scale(width * 0.5, height * 0.5 * self._aspect_ratio_correction) \
             .rotate_deg(self.angle) \
+            .scale(1, 1 / self._aspect_ratio_correction) \
             .translate(*center)
 
     def get_path(self):