returning _facecolor2d and _edgecolor2d as arrays

When using Poly3dCollection, returned colors for _edgecolor2d
and _facecolor2d colors are tuples. By returning these asarrays we
make sure they have the .size in HandlerPolyCollection.
Also added a test case that would fail without this fix

Co-authored-by: Oscar Gustafsson
Co-authored-by: Chahak Mehta <[email protected]>

Author: sghelichkhani

lib/mpl_toolkits/mplot3d/art3d.py

@@ -1063,15 +1063,15 @@ def get_facecolor(self):
         if not hasattr(self, '_facecolors2d'):
             self.axes.M = self.axes.get_proj()
             self.do_3d_projection()
-        return self._facecolors2d
+        return np.asarray(self._facecolors2d)
 
     def get_edgecolor(self):
         # docstring inherited
         # self._edgecolors2d is not initialized until do_3d_projection
         if not hasattr(self, '_edgecolors2d'):
             self.axes.M = self.axes.get_proj()
             self.do_3d_projection()
-        return self._edgecolors2d
+        return np.asarray(self._edgecolors2d)
 
 
 def poly_collection_2d_to_3d(col, zs=0, zdir='z'):

lib/mpl_toolkits/mplot3d/tests/test_legend3d.py

@@ -106,3 +106,16 @@ def test_contourf_legend_elements():
     assert all(isinstance(a, Rectangle) for a in artists)
     assert all(same_color(a.get_facecolor(), c)
                for a, c in zip(artists, expected_colors))
+
+
+def test_legend_Poly3dCollection():
+
+    verts = np.asarray([[0, 0, 0], [0, 1, 1], [1, 0, 1]])
+    mesh = art3d.Poly3DCollection([verts], label="surface")
+
+    fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
+    mesh.set_edgecolor('k')
+    handle = ax.add_collection3d(mesh)
+    leg = ax.legend()
+    assert (leg.legend_handles[0].get_facecolor()
+            == handle.get_facecolor()).all()