Test redrawing from one point

dstansby · dstansby · commit 0554f6e046b7 · 2021-05-03T10:57:05.000+01:00
diff --git a/lib/matplotlib/tests/test_widgets.py b/lib/matplotlib/tests/test_widgets.py
@@ -598,3 +598,29 @@ def test_polygon_selector_remove_first_point():
                       polygon_place_vertex(*verts[0]) +
                       polygon_remove_vertex(*verts[0]))
     check_polygon_selector(event_sequence, verts[1:], 2)
+
+
+def test_polygon_selector_redraw():
+    verts = [(50, 50), (150, 50), (50, 150)]
+    event_sequence = (polygon_place_vertex(*verts[0]) +
+                      polygon_place_vertex(*verts[1]) +
+                      polygon_place_vertex(*verts[2]) +
+                      polygon_place_vertex(*verts[0]) +
+                      # Polygon completed, now remove first two verts
+                      polygon_remove_vertex(*verts[1]) +
+                      polygon_remove_vertex(*verts[2]) +
+                      # At this point the tool should be reset so we can add
+                      # more vertices
+                      polygon_place_vertex(*verts[1]))
+
+    ax = get_ax()
+
+    def onselect(vertices):
+        pass
+
+    tool = widgets.PolygonSelector(ax, onselect)
+    for (etype, event_args) in event_sequence:
+        do_event(tool, etype, **event_args)
+    # After removing two verts, only one remains, and the
+    # selector should be automatically resete
+    assert tool.verts == verts[0:2]
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -2795,6 +2795,12 @@ class PolygonSelector(_SelectorWidget):
     Examples
     --------
     :doc:`/gallery/widgets/polygon_selector_demo`
+
+    Notes
+    -----
+    If only one point remains after removing points, the selector reverts to an
+    incomplete state and you can start drawing a new polygon from the existing
+    point.
     """
 
     def __init__(self, ax, onselect, useblit=False,
