Allow Rectangle and Ellipse selectors to be rotated

dstansby · dstansby · commit fdeed45539a1 · 2021-04-04T22:04:09.000+01:00
diff --git a/doc/users/next_whats_new/selector_rotate.rst b/doc/users/next_whats_new/selector_rotate.rst
@@ -0,0 +1,7 @@
+Rotating selectors
+------------------
+
+The `~matplotlib.widgets.RectangleSelector` and
+`~matplotlib.widgets.EllipseSelector` can now be rotated by pressing the 'r' key,
+and dragging one of their control points. The rotation is done about the first
+vertex placed when drawing the selector.
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -779,10 +779,22 @@ 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(
+        return (transforms.BboxTransformTo(bbox) +
+                transforms.Affine2D().rotate_deg_around(
                     bbox.x0, bbox.y0, self.angle))
 
+    def _get_translate_rotate_transform(self):
+        """
+        Return a transform that translates the LH corner to the origin,
+        and de-rotates the rectangle.
+        """
+        rotate = transforms.Affine2D().rotate_deg_around(self.get_x(),
+                                                         self.get_y(),
+                                                         -self.angle)
+        translate = transforms.Affine2D().translate(-self.get_x(),
+                                                    -self.get_y())
+        return rotate + translate
+
     def get_x(self):
         """Return the left coordinate of the rectangle."""
         return self._x0
diff --git a/lib/matplotlib/tests/test_widgets.py b/lib/matplotlib/tests/test_widgets.py
@@ -143,6 +143,32 @@ def onselect(epress, erelease):
         tool._corner_handles.artist.get_markeredgecolor(), 'b')
 
 
+def test_rectangle_rotate():
+    ax = get_ax()
+
+    def onselect(epress, erelease):
+        pass
+
+    tool = widgets.RectangleSelector(ax, onselect=onselect, interactive=True,
+                                     state_modifier_keys={'rotate': 'r'})
+    # Draw rectangle
+    do_event(tool, 'press', xdata=100, ydata=100)
+    do_event(tool, 'onmove', xdata=130, ydata=140)
+    do_event(tool, 'release', xdata=130, ydata=140)
+    assert tool.extents == (100, 130, 100, 140)
+
+    # Rotate by 45 degrees anticlockwise
+    do_event(tool, 'press', xdata=130, ydata=140, key='r')
+    do_event(tool, 'onmove', xdata=100, ydata=150, key='r')
+    do_event(tool, 'release', xdata=100, ydata=200, key='r')
+    # Extents shouldn't change (as shape of rectangle hasn't changed)
+    assert tool.extents == (100, 130, 100, 140)
+    # Corners should move
+    # The third corner is at (100, 150), as the diagonal of the rectangle has
+    # length 50
+    assert tool.corners == ((100, 124, 100, 76), (100, 118, 150, 132))
+
+
 def check_span(*args, **kwargs):
     ax = get_ax()
 
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
