set_dashes does not support offset=None anymore.

This was deprecated in 3.3 (eb76378) and removed in most places in
c51ae6d; this patch removes supports on the C side and mentions of it
in docs.

Also remove the `dashobj == NULL && dashobj == Py_None` check, which can
never be true.

Author: anntzer

lib/matplotlib/backend_bases.py

@@ -914,15 +914,13 @@ def set_dashes(self, dash_offset, dash_list):
 
         Parameters
         ----------
-        dash_offset : float or None
+        dash_offset : float
             The offset (usually 0).
         dash_list : array-like or None
-            The on-off sequence as points.
+            The on-off sequence as points.  None specifies a solid line.
 
         Notes
         -----
-        ``(None, None)`` specifies a solid line.
-
         See p. 107 of to PostScript `blue book`_ for more info.
 
         .. _blue book: https://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF

src/py_converters.cpp

@@ -212,33 +212,13 @@ int convert_dashes(PyObject *dashobj, void *dashesp)
 {
     Dashes *dashes = (Dashes *)dashesp;
 
-    if (dashobj == NULL && dashobj == Py_None) {
-        return 1;
-    }
-
-    PyObject *dash_offset_obj = NULL;
     double dash_offset = 0.0;
     PyObject *dashes_seq = NULL;
 
-    if (!PyArg_ParseTuple(dashobj, "OO:dashes", &dash_offset_obj, &dashes_seq)) {
+    if (!PyArg_ParseTuple(dashobj, "dO:dashes", &dash_offset, &dashes_seq)) {
         return 0;
     }
 
-    if (dash_offset_obj != Py_None) {
-        dash_offset = PyFloat_AsDouble(dash_offset_obj);
-        if (PyErr_Occurred()) {
-            return 0;
-        }
-    } else {
-        if (PyErr_WarnEx(PyExc_FutureWarning,
-                         "Passing the dash offset as None is deprecated since "
-                         "Matplotlib 3.3 and will be removed in Matplotlib 3.5; "
-                         "pass it as zero instead.",
-                         1)) {
-            return 0;
-        }
-    }
-
     if (dashes_seq == Py_None) {
         return 1;
     }