artist.set_picker(False) no longer keeps artists pickable

anntzer · anntzer · commit 509e5dd4381f · 2020-11-27T12:06:00.000+01:00
The documentation for `set_picker` currently states that `None` disables
picking, `True` enables picking, and a custom callable implements, well,
custom picking behavior.  It turns out that `False` *also* enables
picking, because the relevant check is implemented in `Artist.pickable`,
which strictly checks `picker is not None` (and also checks that the
artist has been added to a figure).  This can indeed be verified with
```python
from pylab import *
plot([1, 2], picker=False); gcf().canvas.mpl_connect("pick_event", print)
```
and clicking on the line.  Strictly speaking, the docs state nothing
about `False`, so the behavior does not violate the docs, but that's
clearly non-optimal behavior, which I'm proposing to change here.
diff --git a/doc/api/next_api_changes/behavior/19031-AL.rst b/doc/api/next_api_changes/behavior/19031-AL.rst
@@ -0,0 +1,4 @@
+``artist.set_picker(False)`` disables artist picking
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, setting the ``picker`` property of an artist to any non-None value, including ``False``, would keep picking enabled.  This was deemed a bug; now, truthy values enable picking and falsy ones disable it.  The default is now ``False`` instead of ``None``, but both mean that picking is disabled by default.
diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
@@ -111,7 +111,7 @@ def __init__(self):
         self._clippath = None
         self._clipon = True
         self._label = ''
-        self._picker = None
+        self._picker = False
         self._contains = None
         self._rasterized = False
         self._agg_filter = None
@@ -496,7 +496,7 @@ def pickable(self):
         --------
         set_picker, get_picker, pick
         """
-        return self.figure is not None and self._picker is not None
+        return self.figure is not None and self._picker
 
     def pick(self, mouseevent):
         """
@@ -539,14 +539,12 @@ def set_picker(self, picker):
 
         Parameters
         ----------
-        picker : None or bool or callable
+        picker : bool or callable
             This can be one of the following:
 
-            - *None*: Picking is disabled for this artist (default).
-
-            - A boolean: If *True* then picking will be enabled and the
-              artist will fire a pick event if the mouse event is over
-              the artist.
+            - A boolean: Whether picking is enabled, i.e. whether the
+              artist fires a pick event when the mouse event occurs over
+              the artist.  The default is False, i.e. picking is disabled.
 
             - A function: If picker is callable, it is a user supplied
               function which determines whether the artist is hit by the
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -123,7 +123,8 @@ def get_verts(self):
     def _process_radius(self, radius):
         if radius is not None:
             return radius
-        if isinstance(self._picker, Number):
+        if (isinstance(self._picker, Number)
+                and not isinstance(self._picker, bool)):
             _radius = self._picker
         else:
             if self.get_edgecolor()[3] == 0:
