matplotlib · dstansby · May 16, 2021 · May 18, 2021 · Jun 27, 2021 · Jul 22, 2021
diff --git a/doc/users/next_whats_new/selector_rotate.rst b/doc/users/next_whats_new/selector_rotate.rst
@@ -0,0 +1,8 @@
+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. This is currently only
+implemented for equal-aspect axes. The rotation is done about the
+first vertex placed when drawing the selector.
diff --git a/lib/matplotlib/tests/test_widgets.py b/lib/matplotlib/tests/test_widgets.py
@@ -190,6 +190,75 @@ def onselect(epress, erelease):
         tool._corner_handles.artist.get_markeredgecolor(), 'b')
 
 
+@pytest.mark.parametrize('selector_class', [widgets.RectangleSelector,
+                                            widgets.EllipseSelector])
+def test_rectangle_rotate(selector_class):
+    ax = get_ax()
+
+    def onselect(epress, erelease):
+        pass
+
+    tool = selector_class(ax, onselect=onselect, interactive=True)
+    # 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 anticlockwise using top-right corner
+    do_event(tool, 'on_key_press', key='r')
+    do_event(tool, 'press', xdata=130, ydata=140)
+    do_event(tool, 'onmove', xdata=100, ydata=150)
+    do_event(tool, 'release', xdata=100, ydata=200)
+    do_event(tool, 'on_key_release', 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 (it is a 3,4,5 scaled right angled triangle)
+    assert tool.corners == ((100, 124, 100, 76), (100, 118, 150, 132))
+
+    # Scale using top-right corner
+    do_event(tool, 'press', xdata=100, ydata=150)
+    do_event(tool, 'onmove', xdata=100, ydata=125)
+    do_event(tool, 'release', xdata=100, ydata=125)
+    assert tool.extents == (100, 115, 100, 120)
+    # The bottom-left corner doesn't move, the top-right moves to (100, 125)
+    assert tool.corners == ((100, 112, 100, 88), (100, 109, 125, 116))
+
+
+@pytest.mark.parametrize('selector_class', [widgets.RectangleSelector,
+                                            widgets.EllipseSelector])
+def test_rotate_warning(selector_class):
+    # Check that a warning is raised when trying to rotate on a
+    # non-equal aspect Axes.
+    ax = get_ax()
+
+    def onselect(epress, erelease):
+        pass
+
+    tool = selector_class(ax, onselect=onselect, interactive=True)
+    ax.set_aspect(2)
+
+    # 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)
+    old_corners = tool.corners
+
+    # Try to rotate
+    do_event(tool, 'on_key_press', key='r')
+    do_event(tool, 'press', xdata=130, ydata=140)
+    # Check warning is raised
+    with pytest.warns(UserWarning, match='Rotation is only implemented for '
+                                         'equal-aspect Axes.'):
+        do_event(tool, 'onmove', xdata=100, ydata=150)
+    do_event(tool, 'release', xdata=100, ydata=200)
+    do_event(tool, 'on_key_release', key='r')
+    # Check that corners haven't moved
+    assert tool.corners == old_corners
+
+
 def check_span(*args, **kwargs):
     ax = get_ax()