Contour kwarg for negative_linestyles

andrew-fennell · andrew-fennell · commit bf46fece1c1d · 2022-05-23T00:05:28.000-05:00
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -721,10 +721,10 @@ class ContourSet(cm.ScalarMappable, ContourLabeler):
 
     def __init__(self, ax, *args,
                  levels=None, filled=False, linewidths=None, linestyles=None,
-                 hatches=(None,), alpha=None, origin=None, extent=None,
-                 cmap=None, colors=None, norm=None, vmin=None, vmax=None,
-                 extend='neither', antialiased=None, nchunk=0, locator=None,
-                 transform=None,
+                 negative_linestyles=None, hatches=(None,), alpha=None,
+                 origin=None, extent=None, cmap=None, colors=None, norm=None,
+                 vmin=None, vmax=None, extend='neither', antialiased=None,
+                 nchunk=0, locator=None, transform=None,
                  **kwargs):
         """
         Draw contour lines or filled regions, depending on
@@ -775,6 +775,7 @@ def __init__(self, ax, *args,
         self.filled = filled
         self.linewidths = linewidths
         self.linestyles = linestyles
+        self.negative_linestyles = negative_linestyles
         self.hatches = hatches
         self.alpha = alpha
         self.origin = origin
@@ -1296,10 +1297,14 @@ def _process_linewidths(self):
     def _process_linestyles(self):
         linestyles = self.linestyles
         Nlev = len(self.levels)
+        neg_ls = self.negative_linestyles
         if linestyles is None:
             tlinestyles = ['solid'] * Nlev
             if self.monochrome:
-                neg_ls = mpl.rcParams['contour.negative_linestyle']
+                # If negative_linestyles was not defined as a kwarg,
+                # define negative_linestyles with rcParams
+                if not neg_ls:
+                    neg_ls = mpl.rcParams['contour.negative_linestyle']
                 eps = - (self.zmax - self.zmin) * 1e-15
                 for i, lev in enumerate(self.levels):
                     if lev < eps:
@@ -1764,6 +1769,18 @@ def _initialize_x_y(self, z):
     iterable is shorter than the number of contour levels
     it will be repeated as necessary.
 
+negative_linestyles : *None* or str, optional
+                      {'solid', 'dashed', 'dashdot', 'dotted'}
+    *Only applies to* `.contour`.
+
+    If *negative_linestyles* is *None*, the default is 'dashed' for
+    negative contours.
+
+    *negative_linestyles* can also be an iterable of the above
+    strings specifying a set of linestyles to be used. If this
+    iterable is shorter than the number of contour levels
+    it will be repeated as necessary.
+
 hatches : list[str], optional
     *Only applies to* `.contourf`.
 
