Merge pull request matplotlib#21881 from dstansby/verts-setter

Author: anntzer

doc/users/next_whats_new/polygon_vert_setter.rst

@@ -0,0 +1,6 @@
+Setting PolygonSelector vertices
+--------------------------------
+The vertices of `~matplotlib.widgets.PolygonSelector` can now be set
+programmatically by using the `~matplotlib.widgets.PolygonSelector.verts`
+property. Setting the vertices this way will reset the selector, and create
+a new complete selector with the supplied vertices.

lib/matplotlib/tests/test_widgets.py

@@ -1442,6 +1442,28 @@ def onselect(vertices):
     assert tool.verts == verts[0:2]
 
 
+@check_figures_equal()
+def test_polygon_selector_verts_setter(fig_test, fig_ref):
+    verts = [(0.1, 0.4), (0.5, 0.9), (0.3, 0.2)]
+    ax_test = fig_test.add_subplot()
+
+    def onselect(vertices):
+        pass
+
+    tool_test = widgets.PolygonSelector(ax_test, onselect)
+    tool_test.verts = verts
+    assert tool_test.verts == verts
+
+    ax_ref = fig_ref.add_subplot()
+    tool_ref = widgets.PolygonSelector(ax_ref, onselect)
+    event_sequence = (polygon_place_vertex(*verts[0]) +
+                      polygon_place_vertex(*verts[1]) +
+                      polygon_place_vertex(*verts[2]) +
+                      polygon_place_vertex(*verts[0]))
+    for (etype, event_args) in event_sequence:
+        do_event(tool_ref, etype, **event_args)
+
+
 @pytest.mark.parametrize(
     "horizOn, vertOn",
     [(True, True), (True, False), (False, True)],

lib/matplotlib/widgets.py

@@ -3786,6 +3786,22 @@ def verts(self):
         """The polygon vertices, as a list of ``(x, y)`` pairs."""
         return list(zip(self._xs[:-1], self._ys[:-1]))
 
+    @verts.setter
+    def verts(self, xys):
+        """
+        Set the polygon vertices.
+
+        This will remove any pre-existing vertices, creating a complete polygon
+        with the new vertices.
+        """
+        self._xs = [xy[0] for xy in xys]
+        self._xs.append(self._xs[0])
+        self._ys = [xy[1] for xy in xys]
+        self._ys.append(self._ys[0])
+        self._selection_completed = True
+        self.set_visible(True)
+        self._draw_polygon()
+
 
 class Lasso(AxesWidget):
     """