Allow empty linestyle for collections

oscargus · oscargus · commit 15f37d833543 · 2022-05-26T16:42:20.000+02:00
diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
@@ -105,9 +105,9 @@ def __init__(self,
             Face color for each patch making up the collection.
         linewidths : float or list of floats, default: :rc:`patch.linewidth`
             Line width for each patch making up the collection.
-        linestyles : str or tuple or list thereof, default: 'solid'
-            Valid strings are ['solid', 'dashed', 'dashdot', 'dotted', '-',
-            '--', '-.', ':']. Dash tuples should be of the form::
+        linestyles : {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} \
+or list thereof, default: 'solid'
+            Dash tuples should be of the form::
 
                 (offset, onoffseq),
 
@@ -586,14 +586,15 @@ def set_linestyle(self, ls):
         """
         Set the linestyle(s) for the collection.
 
-        ===========================   =================
-        linestyle                     description
-        ===========================   =================
-        ``'-'`` or ``'solid'``        solid line
-        ``'--'`` or  ``'dashed'``     dashed line
-        ``'-.'`` or  ``'dashdot'``    dash-dotted line
-        ``':'`` or ``'dotted'``       dotted line
-        ===========================   =================
+        ==========================================  =================
+        linestyle                                   description
+        ==========================================  =================
+        ``'-'`` or ``'solid'``                      solid line
+        ``'--'`` or  ``'dashed'``                   dashed line
+        ``'-.'`` or  ``'dashdot'``                  dash-dotted line
+        ``':'`` or ``'dotted'``                     dotted line
+        ``'none'``, ``'None'``, ``' '``, or ``''``  draw nothing
+        ==========================================  =================
 
         Alternatively a dash tuple of the following form can be provided::
 
@@ -603,14 +604,12 @@ def set_linestyle(self, ls):
 
         Parameters
         ----------
-        ls : str or tuple or list thereof
-            Valid values for individual linestyles include {'-', '--', '-.',
-            ':', '', (offset, on-off-seq)}. See `.Line2D.set_linestyle` for a
-            complete description.
+        ls : {'-', '--', '-.', ':', '', (offset, on-off-seq), ...} \
+or list thereof, default: 'solid'
+            See `.Line2D.set_linestyle` for a complete description.
         """
         try:
             if isinstance(ls, str):
-                ls = cbook.ls_mapper.get(ls, ls)
                 dashes = [mlines._get_dash_pattern(ls)]
             else:
                 try:
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -29,17 +29,26 @@
 _log = logging.getLogger(__name__)
 
 
-def _get_dash_pattern(style):
+def _get_dash_pattern(style, return_ls=False):
     """Convert linestyle to dash pattern."""
-    # go from short hand -> full strings
     if isinstance(style, str):
+        # check valid string
+        _api.check_in_list([*Line2D._lineStyles, *ls_mapper_r], ls=style)
+        # go from short hand -> full strings
         style = ls_mapper.get(style, style)
+        # normalize empty style
+        if style in ('', ' ', 'none'):
+            style = 'None'
+        ls = style
+    else:
+        ls = 'dashed'
+
     # un-dashed styles
-    if style in ['solid', 'None']:
+    if style in ('solid', 'None'):
         offset = 0
         dashes = None
     # dashed styles
-    elif style in ['dashed', 'dashdot', 'dotted']:
+    elif style in ('dashed', 'dashdot', 'dotted'):
         offset = 0
         dashes = tuple(rcParams['lines.{}_pattern'.format(style)])
     #
@@ -52,12 +61,22 @@ def _get_dash_pattern(style):
 
     # normalize offset to be positive and shorter than the dash cycle
     if dashes is not None:
+        if any(dash < 0.0 for dash in dashes):
+            raise ValueError(
+                "All values in the dash list must be non-negative")
+        if len(dashes) and not any(dash > 0.0 for dash in dashes):
+            raise ValueError(
+                'At least one value in the dash list must be positive')
+        if offset is None:
+            raise ValueError(f'Unrecognized linestyle: {style!r}')
         dsum = sum(dashes)
         if dsum:
             offset %= dsum
 
-    return offset, dashes
-
+    if return_ls:
+        return (offset, dashes), ls
+    else:
+        return offset, dashes
 
 def _scale_dashes(offset, dashes, lw):
     if not rcParams['lines.scale_dashes']:
@@ -223,6 +242,7 @@ class Line2D(Artist):
         '-.':   '_draw_dash_dot',
         ':':    '_draw_dotted',
         'None': '_draw_nothing',
+        'none': '_draw_nothing',
         ' ':    '_draw_nothing',
         '':     '_draw_nothing',
     }
@@ -1108,16 +1128,8 @@ def set_linestyle(self, ls):
 
             For examples see :doc:`/gallery/lines_bars_and_markers/linestyles`.
         """
-        if isinstance(ls, str):
-            if ls in [' ', '', 'none']:
-                ls = 'None'
-            _api.check_in_list([*self._lineStyles, *ls_mapper_r], ls=ls)
-            if ls not in self._lineStyles:
-                ls = ls_mapper_r[ls]
-            self._linestyle = ls
-        else:
-            self._linestyle = '--'
-        self._unscaled_dash_pattern = _get_dash_pattern(ls)
+        self._unscaled_dash_pattern, self._linestyle = _get_dash_pattern(ls,
+                                                                         True)
         self._dash_pattern = _scale_dashes(
             *self._unscaled_dash_pattern, self._linewidth)
         self.stale = True
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -421,10 +421,8 @@ def set_linestyle(self, ls):
         """
         if ls is None:
             ls = "solid"
-        if ls in [' ', '', 'none']:
-            ls = 'None'
-        self._linestyle = ls
-        self._unscaled_dash_pattern = mlines._get_dash_pattern(ls)
+        self._unscaled_dash_pattern, self._linestyle = (
+            mlines._get_dash_pattern(ls, True))
         self._dash_pattern = mlines._scale_dashes(
             *self._unscaled_dash_pattern, self._linewidth)
         self.stale = True
