DOC: Document default join style

in the same way as the default cap styles.

Author: StefRe

lib/matplotlib/lines.py

@@ -1292,6 +1292,8 @@ def set_dash_joinstyle(self, s):
         """
         How to join segments of the line if it `~Line2D.is_dashed`.
 
+        The default joinstyle is :rc:`lines.dash_joinstyle`.
+
         Parameters
         ----------
         s : `.JoinStyle` or %(JoinStyle)s
@@ -1306,6 +1308,8 @@ def set_solid_joinstyle(self, s):
         """
         How to join segments if the line is solid (not `~Line2D.is_dashed`).
 
+        The default joinstyle is :rc:`lines.solid_joinstyle`.
+
         Parameters
         ----------
         s : `.JoinStyle` or %(JoinStyle)s

lib/matplotlib/patches.py

@@ -494,6 +494,9 @@ def set_joinstyle(self, s):
         """
         Set the `.JoinStyle`.
 
+        The default joinstyle is 'round' for `.FancyArrowPatch` and 'miter' for
+        all other patches.
+
         Parameters
         ----------
         s : `.JoinStyle` or %(JoinStyle)s