matplotlib · QuLogic · Aug 11, 2020 · Oct 26, 2019 · Nov 11, 2019 · Dec 22, 2019
diff --git a/doc/users/next_whats_new/2019-12-22_transform-rotates-text-direction.rst b/doc/users/next_whats_new/2019-12-22_transform-rotates-text-direction.rst
@@ -0,0 +1,7 @@
+:orphan:
+
+Transform can rotate text direction
+-----------------------------------
+The new `.Text` parameter ``transform_rotates_text`` now sets whether
+rotations of the transform affect the text direction.
+
diff --git a/examples/text_labels_and_annotations/text_rotation_relative_to_line.py b/examples/text_labels_and_annotations/text_rotation_relative_to_line.py
@@ -10,8 +10,8 @@
 to something on the plot.  In this case, the correct angle won't be
 the angle of that object in the plot coordinate system, but the angle
 that that object APPEARS in the screen coordinate system.  This angle
-is found by transforming the angle from the plot to the screen
-coordinate system, as shown in the example below.
+can be determined automatically by setting the parameter
+*transform_rotates_text*, as shown in the example below.
 """
 
 import matplotlib.pyplot as plt
@@ -31,12 +31,12 @@
 
 # Rotate angle
 angle = 45
-trans_angle = ax.transData.transform_angles([45], l2.reshape((1, 2)))[0]
 
 # Plot text
 th1 = ax.text(*l1, 'text not rotated correctly', fontsize=16,
               rotation=angle, rotation_mode='anchor')
 th2 = ax.text(*l2, 'text rotated correctly', fontsize=16,
-              rotation=trans_angle, rotation_mode='anchor')
+              rotation=angle, rotation_mode='anchor',
+              transform_rotates_text=True)
 
 plt.show()
diff --git a/lib/matplotlib/tests/test_text.py b/lib/matplotlib/tests/test_text.py
@@ -10,6 +10,7 @@
 from matplotlib.backend_bases import MouseEvent
 import matplotlib.patches as mpatches
 import matplotlib.pyplot as plt
+import matplotlib.transforms as mtransforms
 from matplotlib.testing.decorators import check_figures_equal, image_comparison
 
 
@@ -689,3 +690,12 @@ def test_fontproperties_kwarg_precedence():
     text2 = plt.ylabel("counts", size=40.0, fontproperties='Times New Roman')
     assert text1.get_size() == 40.0
     assert text2.get_size() == 40.0
+
+
+def test_transform_rotates_text():
+    ax = plt.gca()
+    transform = mtransforms.Affine2D().rotate_deg(30)
+    text = ax.text(0, 0, 'test', transform=transform,
+                   transform_rotates_text=True)
+    result = text.get_rotation()
+    assert_almost_equal(result, 30)
diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -136,6 +136,7 @@ def __init__(self,
                  rotation_mode=None,
                  usetex=None,          # defaults to rcParams['text.usetex']
                  wrap=False,
+                 transform_rotates_text=False,
                  **kwargs
                  ):
         """
@@ -157,6 +158,7 @@ def __init__(self,
         self.set_horizontalalignment(horizontalalignment)
         self._multialignment = multialignment
         self._rotation = rotation
+        self._transform_rotates_text = transform_rotates_text
         self._bbox_patch = None  # a FancyBboxPatch instance
         self._renderer = None
         if linespacing is None:
@@ -228,7 +230,20 @@ def _get_multialignment(self):
 
     def get_rotation(self):
         """Return the text angle in degrees between 0 and 360."""
-        return get_rotation(self._rotation)  # string_or_number -> number
+        if self.get_transform_rotates_text():
+            angle = get_rotation(self._rotation)
+            x, y = self.get_unitless_position()
+            angles = [angle, ]
+            pts = [[x, y]]
+            return self.get_transform().transform_angles(angles, pts).item(0)
+        else:
+            return get_rotation(self._rotation)  # string_or_number -> number
+
+    def get_transform_rotates_text(self):
+        """
+        Return whether rotations of the transform affect the text direction.
+        """
+        return self._transform_rotates_text
 
     def set_rotation_mode(self, m):
         """
@@ -259,6 +274,7 @@ def update_from(self, other):
         self._fontproperties = other._fontproperties.copy()
         self._usetex = other._usetex
         self._rotation = other._rotation
+        self._transform_rotates_text = other._transform_rotates_text
         self._picker = other._picker
         self._linespacing = other._linespacing
         self.stale = True
@@ -843,6 +859,7 @@ def get_prop_tup(self, renderer=None):
                 self._verticalalignment, self._horizontalalignment,
                 hash(self._fontproperties),
                 self._rotation, self._rotation_mode,
+                self._transform_rotates_text,
                 self.figure.dpi, weakref.ref(renderer),
                 self._linespacing
                 )
@@ -1132,6 +1149,17 @@ def set_rotation(self, s):
         self._rotation = s
         self.stale = True
 
+    def set_transform_rotates_text(self, t):
+        """
+        Whether rotations of the transform affect the text direction.
+
+        Parameters
+        ----------
+        t : bool
+        """
+        self._transform_rotates_text = t
+        self.stale = True
+
     def set_verticalalignment(self, align):
         """
         Set the vertical alignment.